greenplumn lock 源码
greenplumn lock 代码
文件路径：/src/backend/storage/lmgr/lock.c
/*-------------------------------------------------------------------------
*
* lock.c
* POSTGRES primary lock mechanism
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/storage/lmgr/lock.c
*
* NOTES
* A lock table is a shared memory hash table. When
* a process tries to acquire a lock of a type that conflicts
* with existing locks, it is put to sleep using the routines
* in storage/lmgr/proc.c.
*
* For the most part, this code should be invoked via lmgr.c
* or another lock-management module, not directly.
*
* Interface:
*
* InitLocks(), GetLocksMethodTable(), GetLockTagsMethodTable(),
* LockAcquire(), LockRelease(), LockReleaseAll(),
* LockCheckConflicts(), GrantLock()
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "access/transam.h"
#include "access/twophase.h"
#include "access/twophase_rmgr.h"
#include "access/xact.h"
#include "access/xlog.h"
#include "miscadmin.h"
#include "pg_trace.h"
#include "pgstat.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/sinvaladt.h"
#include "storage/spin.h"
#include "storage/standby.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
#include "utils/resscheduler.h"
#include "utils/resource_manager.h"
#include "utils/resowner_private.h"
#include "cdb/cdbvars.h"
/* This configuration variable is used to set the lock table size */
int max_locks_per_xact; /* set by guc.c */
#define NLOCKENTS() \
mul_size(max_locks_per_xact, add_size(MaxBackends, max_prepared_xacts))
#define NRESLOCKENTS() \
MaxResourceQueues
#define NRESPROCLOCKENTS() \
mul_size(MaxResourceQueues, MaxBackends)
/*
* Data structures defining the semantics of the standard lock methods.
*
* The conflict table defines the semantics of the various lock modes.
*/
static const LOCKMASK LockConflicts[] = {
0,
/* AccessShareLock */
LOCKBIT_ON(AccessExclusiveLock),
/* RowShareLock */
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock),
/* RowExclusiveLock */
LOCKBIT_ON(ShareLock) | LOCKBIT_ON(ShareRowExclusiveLock) |
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock),
/* ShareUpdateExclusiveLock */
LOCKBIT_ON(ShareUpdateExclusiveLock) |
LOCKBIT_ON(ShareLock) | LOCKBIT_ON(ShareRowExclusiveLock) |
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock),
/* ShareLock */
LOCKBIT_ON(RowExclusiveLock) | LOCKBIT_ON(ShareUpdateExclusiveLock) |
LOCKBIT_ON(ShareRowExclusiveLock) |
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock),
/* ShareRowExclusiveLock */
LOCKBIT_ON(RowExclusiveLock) | LOCKBIT_ON(ShareUpdateExclusiveLock) |
LOCKBIT_ON(ShareLock) | LOCKBIT_ON(ShareRowExclusiveLock) |
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock),
/* ExclusiveLock */
LOCKBIT_ON(RowShareLock) |
LOCKBIT_ON(RowExclusiveLock) | LOCKBIT_ON(ShareUpdateExclusiveLock) |
LOCKBIT_ON(ShareLock) | LOCKBIT_ON(ShareRowExclusiveLock) |
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock),
/* AccessExclusiveLock */
LOCKBIT_ON(AccessShareLock) | LOCKBIT_ON(RowShareLock) |
LOCKBIT_ON(RowExclusiveLock) | LOCKBIT_ON(ShareUpdateExclusiveLock) |
LOCKBIT_ON(ShareLock) | LOCKBIT_ON(ShareRowExclusiveLock) |
LOCKBIT_ON(ExclusiveLock) | LOCKBIT_ON(AccessExclusiveLock)
};
/* Names of lock modes, for debug printouts */
static const char *const lock_mode_names[] =
{
"INVALID",
"AccessShareLock",
"RowShareLock",
"RowExclusiveLock",
"ShareUpdateExclusiveLock",
"ShareLock",
"ShareRowExclusiveLock",
"ExclusiveLock",
"AccessExclusiveLock"
};
#ifndef LOCK_DEBUG
static bool Dummy_trace = false;
#endif
const LockMethodData default_lockmethod = {
AccessExclusiveLock, /* highest valid lock mode number */
LockConflicts,
lock_mode_names,
#ifdef LOCK_DEBUG
&Trace_locks
#else
&Dummy_trace
#endif
};
const LockMethodData user_lockmethod = {
AccessExclusiveLock, /* highest valid lock mode number */
LockConflicts,
lock_mode_names,
#ifdef LOCK_DEBUG
&Trace_userlocks
#else
&Dummy_trace
#endif
};
const LockMethodData resource_lockmethod = {
AccessExclusiveLock, /* highest valid lock mode number */
LockConflicts,
lock_mode_names,
#ifdef LOCK_DEBUG
&Trace_locks
#else
&Dummy_trace
#endif
};
/*
* map from lock method id to the lock table data structures
*/
const LockMethod LockMethods[] = {
NULL,
&default_lockmethod,
&user_lockmethod,
&resource_lockmethod
};
/* Record that's written to 2PC state file when a lock is persisted */
typedef struct TwoPhaseLockRecord
{
LOCKTAG locktag;
LOCKMODE lockmode;
} TwoPhaseLockRecord;
/*
* Count of the number of fast path lock slots we believe to be used. This
* might be higher than the real number if another backend has transferred
* our locks to the primary lock table, but it can never be lower than the
* real value, since only we can acquire locks on our own behalf.
*/
static int FastPathLocalUseCount = 0;
/* Macros for manipulating proc->fpLockBits */
#define FAST_PATH_BITS_PER_SLOT 3
#define FAST_PATH_LOCKNUMBER_OFFSET 1
#define FAST_PATH_MASK ((1 << FAST_PATH_BITS_PER_SLOT) - 1)
#define FAST_PATH_GET_BITS(proc, n) \
(((proc)->fpLockBits >> (FAST_PATH_BITS_PER_SLOT * n)) & FAST_PATH_MASK)
#define FAST_PATH_BIT_POSITION(n, l) \
(AssertMacro((l) >= FAST_PATH_LOCKNUMBER_OFFSET), \
AssertMacro((l) < FAST_PATH_BITS_PER_SLOT+FAST_PATH_LOCKNUMBER_OFFSET), \
AssertMacro((n) < FP_LOCK_SLOTS_PER_BACKEND), \
((l) - FAST_PATH_LOCKNUMBER_OFFSET + FAST_PATH_BITS_PER_SLOT * (n)))
#define FAST_PATH_SET_LOCKMODE(proc, n, l) \
(proc)->fpLockBits |= UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l)
#define FAST_PATH_CLEAR_LOCKMODE(proc, n, l) \
(proc)->fpLockBits &= ~(UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l))
#define FAST_PATH_CHECK_LOCKMODE(proc, n, l) \
((proc)->fpLockBits & (UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l)))
/*
* fpHoldTillEndXactBits is used for GDD
* bits is the result of FAST_PATH_GET_BITS(proc, n)
* we simply set the whole bits to the corresponding bits
* as fpLockBits.
*/
#define FAST_PATH_SET_HOLD_TILL_END_XACT(proc, n, bits) \
(proc)->fpHoldTillEndXactBits |= (((uint64) (bits)) & FAST_PATH_MASK) << (FAST_PATH_BITS_PER_SLOT * (n))
#define FAST_PATH_GET_HOLD_TILL_END_XACT_BITS(proc, n) \
(((proc)->fpHoldTillEndXactBits >> (FAST_PATH_BITS_PER_SLOT * (n))) & FAST_PATH_MASK)
/*
* The fast-path lock mechanism is concerned only with relation locks on
* unshared relations by backends bound to a database. The fast-path
* mechanism exists mostly to accelerate acquisition and release of locks
* that rarely conflict. Because ShareUpdateExclusiveLock is
* self-conflicting, it can't use the fast-path mechanism; but it also does
* not conflict with any of the locks that do, so we can ignore it completely.
*/
#define EligibleForRelationFastPath(locktag, mode) \
((locktag)->locktag_lockmethodid == DEFAULT_LOCKMETHOD && \
(locktag)->locktag_type == LOCKTAG_RELATION && \
(locktag)->locktag_field1 == MyDatabaseId && \
MyDatabaseId != InvalidOid && \
(mode) < ShareUpdateExclusiveLock)
#define ConflictsWithRelationFastPath(locktag, mode) \
((locktag)->locktag_lockmethodid == DEFAULT_LOCKMETHOD && \
(locktag)->locktag_type == LOCKTAG_RELATION && \
(locktag)->locktag_field1 != InvalidOid && \
(mode) > ShareUpdateExclusiveLock)
static bool FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode);
static bool FastPathUnGrantRelationLock(Oid relid, LOCKMODE lockmode);
static bool FastPathTransferRelationLocks(LockMethod lockMethodTable,
const LOCKTAG *locktag, uint32 hashcode);
static PROCLOCK *FastPathGetRelationLockEntry(LOCALLOCK *locallock);
/*
* To make the fast-path lock mechanism work, we must have some way of
* preventing the use of the fast-path when a conflicting lock might be
* present. We partition* the locktag space into FAST_PATH_HASH_BUCKETS
* partitions, and maintain an integer count of the number of "strong" lockers
* in each partition. When any "strong" lockers are present (which is
* hopefully not very often), the fast-path mechanism can't be used, and we
* must fall back to the slower method of pushing matching locks directly
* into the main lock tables.
*
* The deadlock detector does not know anything about the fast path mechanism,
* so any locks that might be involved in a deadlock must be transferred from
* the fast-path queues to the main lock table.
*/
#define FAST_PATH_STRONG_LOCK_HASH_BITS 10
#define FAST_PATH_STRONG_LOCK_HASH_PARTITIONS \
(1 << FAST_PATH_STRONG_LOCK_HASH_BITS)
#define FastPathStrongLockHashPartition(hashcode) \
((hashcode) % FAST_PATH_STRONG_LOCK_HASH_PARTITIONS)
typedef struct
{
slock_t mutex;
uint32 count[FAST_PATH_STRONG_LOCK_HASH_PARTITIONS];
} FastPathStrongRelationLockData;
static volatile FastPathStrongRelationLockData *FastPathStrongRelationLocks;
/*
* Pointers to hash tables containing lock state
*
* The LockMethodLockHash and LockMethodProcLockHash hash tables are in
* shared memory; LockMethodLocalHash is local to each backend.
*/
HTAB *LockMethodLockHash;
HTAB *LockMethodProcLockHash;
HTAB *LockMethodLocalHash;
/* private state for error cleanup */
static LOCALLOCK *StrongLockInProgress;
LOCALLOCK *awaitedLock;
ResourceOwner awaitedOwner;
#ifdef LOCK_DEBUG
/*------
* The following configuration options are available for lock debugging:
*
* TRACE_LOCKS -- give a bunch of output what's going on in this file
* TRACE_USERLOCKS -- same but for user locks
* TRACE_LOCK_OIDMIN-- do not trace locks for tables below this oid
* (use to avoid output on system tables)
* TRACE_LOCK_TABLE -- trace locks on this table (oid) unconditionally
* DEBUG_DEADLOCKS -- currently dumps locks at untimely occasions ;)
*
* Furthermore, but in storage/lmgr/lwlock.c:
* TRACE_LWLOCKS -- trace lightweight locks (pretty useless)
*
* Define LOCK_DEBUG at compile time to get all these enabled.
* --------
*/
int Trace_lock_oidmin = FirstNormalObjectId;
bool Trace_locks = false;
bool Trace_userlocks = false;
int Trace_lock_table = 0;
bool Debug_deadlocks = false;
inline static bool
LOCK_DEBUG_ENABLED(const LOCKTAG *tag)
{
return
(*(LockMethods[tag->locktag_lockmethodid]->trace_flag) &&
((Oid) tag->locktag_field2 >= (Oid) Trace_lock_oidmin))
|| (Trace_lock_table &&
(tag->locktag_field2 == Trace_lock_table));
}
inline static void
LOCK_PRINT(const char *where, const LOCK *lock, LOCKMODE type)
{
if (LOCK_DEBUG_ENABLED(&lock->tag))
elog(LOG,
"%s: lock(%p) id(%u,%u,%u,%u,%u,%u) grantMask(%x) "
"req(%d,%d,%d,%d,%d,%d,%d)=%d "
"grant(%d,%d,%d,%d,%d,%d,%d)=%d wait(%d) type(%s)",
where, lock,
lock->tag.locktag_field1, lock->tag.locktag_field2,
lock->tag.locktag_field3, lock->tag.locktag_field4,
lock->tag.locktag_type, lock->tag.locktag_lockmethodid,
lock->grantMask,
lock->requested[1], lock->requested[2], lock->requested[3],
lock->requested[4], lock->requested[5], lock->requested[6],
lock->requested[7], lock->nRequested,
lock->granted[1], lock->granted[2], lock->granted[3],
lock->granted[4], lock->granted[5], lock->granted[6],
lock->granted[7], lock->nGranted,
lock->waitProcs.size,
LockMethods[LOCK_LOCKMETHOD(*lock)]->lockModeNames[type]);
}
inline static void
PROCLOCK_PRINT(const char *where, const PROCLOCK *proclockP)
{
if (LOCK_DEBUG_ENABLED(&proclockP->tag.myLock->tag))
elog(LOG,
"%s: proclock(%p) lock(%p) method(%u) proc(%p) hold(%x)",
where, proclockP, proclockP->tag.myLock,
PROCLOCK_LOCKMETHOD(*(proclockP)),
proclockP->tag.myProc, (int) proclockP->holdMask);
}
#else /* not LOCK_DEBUG */
#define LOCK_PRINT(where, lock, type) ((void) 0)
#define PROCLOCK_PRINT(where, proclockP) ((void) 0)
#endif /* not LOCK_DEBUG */
static uint32 proclock_hash(const void *key, Size keysize);
void RemoveLocalLock(LOCALLOCK *locallock);
static PROCLOCK *SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc,
const LOCKTAG *locktag, uint32 hashcode, LOCKMODE lockmode);
static void GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner);
static void BeginStrongLockAcquire(LOCALLOCK *locallock, uint32 fasthashcode);
static void FinishStrongLockAcquire(void);
static void WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner);
static void ReleaseLockIfHeld(LOCALLOCK *locallock, bool sessionLock);
static void LockReassignOwner(LOCALLOCK *locallock, ResourceOwner parent);
static bool UnGrantLock(LOCK *lock, LOCKMODE lockmode,
PROCLOCK *proclock, LockMethod lockMethodTable);
static void CleanUpLock(LOCK *lock, PROCLOCK *proclock,
LockMethod lockMethodTable, uint32 hashcode,
bool wakeupNeeded);
static void LockRefindAndRelease(LockMethod lockMethodTable, PGPROC *proc,
LOCKTAG *locktag, LOCKMODE lockmode,
bool decrement_strong_lock_count);
static bool setFPHoldTillEndXact(Oid relid);
static void GetSingleProcBlockerStatusData(PGPROC *blocked_proc,
BlockedProcsData *data);
/*
* InitLocks -- Initialize the lock manager's data structures.
*
* This is called from CreateSharedMemoryAndSemaphores(), which see for
* more comments. In the normal postmaster case, the shared hash tables
* are created here, as well as a locallock hash table that will remain
* unused and empty in the postmaster itself. Backends inherit the pointers
* to the shared tables via fork(), and also inherit an image of the locallock
* hash table, which they proceed to use. In the EXEC_BACKEND case, each
* backend re-executes this code to obtain pointers to the already existing
* shared hash tables and to create its locallock hash table.
*/
void
InitLocks(void)
{
HASHCTL info;
long init_table_size,
max_table_size;
bool found;
/*
* Compute init/max size to request for lock hashtables. Note these
* calculations must agree with LockShmemSize!
*/
max_table_size = NLOCKENTS();
/* Allow for extra entries if resource locking is enabled. */
if (Gp_role == GP_ROLE_DISPATCH && IsResQueueEnabled())
{
max_table_size = add_size(max_table_size, NRESLOCKENTS() );
max_table_size = add_size(max_table_size, NRESPROCLOCKENTS() );
}
init_table_size = max_table_size / 2;
/*
* Allocate hash table for LOCK structs. This stores per-locked-object
* information.
*/
MemSet(&info, 0, sizeof(info));
info.keysize = sizeof(LOCKTAG);
info.entrysize = sizeof(LOCK);
info.num_partitions = NUM_LOCK_PARTITIONS;
LockMethodLockHash = ShmemInitHash("LOCK hash",
init_table_size,
max_table_size,
&info,
HASH_ELEM | HASH_BLOBS | HASH_PARTITION);
/* Assume an average of 2 holders per lock */
max_table_size *= 2;
init_table_size *= 2;
/*
* Allocate hash table for PROCLOCK structs. This stores
* per-lock-per-holder information.
*/
info.keysize = sizeof(PROCLOCKTAG);
info.entrysize = sizeof(PROCLOCK);
info.hash = proclock_hash;
info.num_partitions = NUM_LOCK_PARTITIONS;
LockMethodProcLockHash = ShmemInitHash("PROCLOCK hash",
init_table_size,
max_table_size,
&info,
HASH_ELEM | HASH_FUNCTION | HASH_PARTITION);
/*
* Allocate fast-path structures.
*/
FastPathStrongRelationLocks =
ShmemInitStruct("Fast Path Strong Relation Lock Data",
sizeof(FastPathStrongRelationLockData), &found);
if (!found)
SpinLockInit(&FastPathStrongRelationLocks->mutex);
/*
* Allocate non-shared hash table for LOCALLOCK structs. This stores lock
* counts and resource owner information.
*
* The non-shared table could already exist in this process (this occurs
* when the postmaster is recreating shared memory after a backend crash).
* If so, delete and recreate it. (We could simply leave it, since it
* ought to be empty in the postmaster, but for safety let's zap it.)
*/
if (LockMethodLocalHash)
hash_destroy(LockMethodLocalHash);
info.keysize = sizeof(LOCALLOCKTAG);
info.entrysize = sizeof(LOCALLOCK);
LockMethodLocalHash = hash_create("LOCALLOCK hash",
16,
&info,
HASH_ELEM | HASH_BLOBS);
}
/*
* Fetch the lock method table associated with a given lock
*/
LockMethod
GetLocksMethodTable(const LOCK *lock)
{
LOCKMETHODID lockmethodid = LOCK_LOCKMETHOD(*lock);
Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
return LockMethods[lockmethodid];
}
/*
* Fetch the lock method table associated with a given locktag
*/
LockMethod
GetLockTagsMethodTable(const LOCKTAG *locktag)
{
LOCKMETHODID lockmethodid = (LOCKMETHODID) locktag->locktag_lockmethodid;
Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
return LockMethods[lockmethodid];
}
/*
* Compute the hash code associated with a LOCKTAG.
*
* To avoid unnecessary recomputations of the hash code, we try to do this
* just once per function, and then pass it around as needed. Aside from
* passing the hashcode to hash_search_with_hash_value(), we can extract
* the lock partition number from the hashcode.
*/
uint32
LockTagHashCode(const LOCKTAG *locktag)
{
return get_hash_value(LockMethodLockHash, (const void *) locktag);
}
/*
* Compute the hash code associated with a PROCLOCKTAG.
*
* Because we want to use just one set of partition locks for both the
* LOCK and PROCLOCK hash tables, we have to make sure that PROCLOCKs
* fall into the same partition number as their associated LOCKs.
* dynahash.c expects the partition number to be the low-order bits of
* the hash code, and therefore a PROCLOCKTAG's hash code must have the
* same low-order bits as the associated LOCKTAG's hash code. We achieve
* this with this specialized hash function.
*/
static uint32
proclock_hash(const void *key, Size keysize)
{
const PROCLOCKTAG *proclocktag = (const PROCLOCKTAG *) key;
uint32 lockhash;
Datum procptr;
Assert(keysize == sizeof(PROCLOCKTAG));
/* Look into the associated LOCK object, and compute its hash code */
lockhash = LockTagHashCode(&proclocktag->myLock->tag);
/*
* To make the hash code also depend on the PGPROC, we xor the proc
* struct's address into the hash code, left-shifted so that the
* partition-number bits don't change. Since this is only a hash, we
* don't care if we lose high-order bits of the address; use an
* intermediate variable to suppress cast-pointer-to-int warnings.
*/
procptr = PointerGetDatum(proclocktag->myProc);
lockhash ^= ((uint32) procptr) << LOG2_NUM_LOCK_PARTITIONS;
return lockhash;
}
/*
* Given two lock modes, return whether they would conflict.
*/
bool
DoLockModesConflict(LOCKMODE mode1, LOCKMODE mode2)
{
LockMethod lockMethodTable = LockMethods[DEFAULT_LOCKMETHOD];
if (lockMethodTable->conflictTab[mode1] & LOCKBIT_ON(mode2))
return true;
return false;
}
/*
* LockHeldByMe -- test whether lock 'locktag' is held with mode 'lockmode'
* by the current transaction
*/
bool
LockHeldByMe(const LOCKTAG *locktag, LOCKMODE lockmode)
{
LOCALLOCKTAG localtag;
LOCALLOCK *locallock;
/*
* See if there is a LOCALLOCK entry for this lock and lockmode
*/
MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
localtag.lock = *locktag;
localtag.mode = lockmode;
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
(void *) &localtag,
HASH_FIND, NULL);
return (locallock && locallock->nLocks > 0);
}
/*
* LockHasWaiters -- look up 'locktag' and check if releasing this
* lock would wake up other processes waiting for it.
*/
bool
LockHasWaiters(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock)
{
LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
LockMethod lockMethodTable;
LOCALLOCKTAG localtag;
LOCALLOCK *locallock;
LOCK *lock;
PROCLOCK *proclock;
LWLock *partitionLock;
bool hasWaiters = false;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
elog(ERROR, "unrecognized lock mode: %d", lockmode);
#ifdef LOCK_DEBUG
if (LOCK_DEBUG_ENABLED(locktag))
elog(LOG, "LockHasWaiters: lock [%u,%u] %s",
locktag->locktag_field1, locktag->locktag_field2,
lockMethodTable->lockModeNames[lockmode]);
#endif
/*
* Find the LOCALLOCK entry for this lock and lockmode
*/
MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
localtag.lock = *locktag;
localtag.mode = lockmode;
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
(void *) &localtag,
HASH_FIND, NULL);
/*
* let the caller print its own error message, too. Do not ereport(ERROR).
*/
if (!locallock || locallock->nLocks <= 0)
{
elog(WARNING, "you don't own a lock of type %s",
lockMethodTable->lockModeNames[lockmode]);
return false;
}
/*
* Check the shared lock table.
*/
partitionLock = LockHashPartitionLock(locallock->hashcode);
LWLockAcquire(partitionLock, LW_SHARED);
/*
* We don't need to re-find the lock or proclock, since we kept their
* addresses in the locallock table, and they couldn't have been removed
* while we were holding a lock on them.
*/
lock = locallock->lock;
LOCK_PRINT("LockHasWaiters: found", lock, lockmode);
proclock = locallock->proclock;
PROCLOCK_PRINT("LockHasWaiters: found", proclock);
/*
* Double-check that we are actually holding a lock of the type we want to
* release.
*/
if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
{
PROCLOCK_PRINT("LockHasWaiters: WRONGTYPE", proclock);
LWLockRelease(partitionLock);
elog(WARNING, "you don't own a lock of type %s",
lockMethodTable->lockModeNames[lockmode]);
RemoveLocalLock(locallock);
return false;
}
/*
* Do the checking.
*/
if ((lockMethodTable->conflictTab[lockmode] & lock->waitMask) != 0)
hasWaiters = true;
LWLockRelease(partitionLock);
return hasWaiters;
}
/*
* LockAcquire -- Check for lock conflicts, sleep if conflict found,
* set lock if/when no conflicts.
*
* Inputs:
* locktag: unique identifier for the lockable object
* lockmode: lock mode to acquire
* sessionLock: if true, acquire lock for session not current transaction
* dontWait: if true, don't wait to acquire lock
*
* Returns one of:
* LOCKACQUIRE_NOT_AVAIL lock not available, and dontWait=true
* LOCKACQUIRE_OK lock successfully acquired
* LOCKACQUIRE_ALREADY_HELD incremented count for lock already held
* LOCKACQUIRE_ALREADY_CLEAR incremented count for lock already clear
*
* In the normal case where dontWait=false and the caller doesn't need to
* distinguish a freshly acquired lock from one already taken earlier in
* this same transaction, there is no need to examine the return value.
*
* Side Effects: The lock is acquired and recorded in lock tables.
*
* NOTE: if we wait for the lock, there is no way to abort the wait
* short of aborting the transaction.
*/
LockAcquireResult
LockAcquire(const LOCKTAG *locktag,
LOCKMODE lockmode,
bool sessionLock,
bool dontWait)
{
return LockAcquireExtended(locktag, lockmode, sessionLock, dontWait,
true, NULL);
}
/*
* LockAcquireExtended - allows us to specify additional options
*
* reportMemoryError specifies whether a lock request that fills the lock
* table should generate an ERROR or not. Passing "false" allows the caller
* to attempt to recover from lock-table-full situations, perhaps by forcibly
* cancelling other lock holders and then retrying. Note, however, that the
* return code for that is LOCKACQUIRE_NOT_AVAIL, so that it's unsafe to use
* in combination with dontWait = true, as the cause of failure couldn't be
* distinguished.
*
* If locallockp isn't NULL, *locallockp receives a pointer to the LOCALLOCK
* table entry if a lock is successfully acquired, or NULL if not.
*/
LockAcquireResult
LockAcquireExtended(const LOCKTAG *locktag,
LOCKMODE lockmode,
bool sessionLock,
bool dontWait,
bool reportMemoryError,
LOCALLOCK **locallockp)
{
LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
LockMethod lockMethodTable;
LOCALLOCKTAG localtag;
LOCALLOCK *locallock;
LOCK *lock;
PROCLOCK *proclock;
bool found;
ResourceOwner owner;
uint32 hashcode;
LWLock *partitionLock;
int status;
bool log_lock = false;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
elog(ERROR, "unrecognized lock mode: %d", lockmode);
if (RecoveryInProgress() && !InRecovery &&
(locktag->locktag_type == LOCKTAG_OBJECT ||
locktag->locktag_type == LOCKTAG_RELATION) &&
lockmode > RowExclusiveLock)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("cannot acquire lock mode %s on database objects while recovery is in progress",
lockMethodTable->lockModeNames[lockmode]),
errhint("Only RowExclusiveLock or less can be acquired on database objects during recovery.")));
#ifdef LOCK_DEBUG
if (LOCK_DEBUG_ENABLED(locktag))
elog(LOG, "LockAcquire: lock [%u,%u] %s",
locktag->locktag_field1, locktag->locktag_field2,
lockMethodTable->lockModeNames[lockmode]);
#endif
/* Identify owner for lock */
if (sessionLock)
owner = NULL;
else
owner = CurrentResourceOwner;
/*
* Find or create a LOCALLOCK entry for this lock and lockmode
*/
MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
localtag.lock = *locktag;
localtag.mode = lockmode;
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
(void *) &localtag,
HASH_ENTER, &found);
/*
* if it's a new locallock object, initialize it
*/
if (!found)
{
locallock->lock = NULL;
locallock->proclock = NULL;
locallock->hashcode = LockTagHashCode(&(localtag.lock));
locallock->istemptable = false; /* will be used later, at prepare */
locallock->nLocks = 0;
locallock->holdsStrongLockCount = false;
locallock->lockCleared = false;
locallock->numLockOwners = 0;
locallock->maxLockOwners = 8;
locallock->lockOwners = NULL; /* in case next line fails */
locallock->lockOwners = (LOCALLOCKOWNER *)
MemoryContextAlloc(TopMemoryContext,
locallock->maxLockOwners * sizeof(LOCALLOCKOWNER));
}
else
{
/* Make sure there will be room to remember the lock */
if (locallock->numLockOwners >= locallock->maxLockOwners)
{
int newsize = locallock->maxLockOwners * 2;
locallock->lockOwners = (LOCALLOCKOWNER *)
repalloc(locallock->lockOwners,
newsize * sizeof(LOCALLOCKOWNER));
locallock->maxLockOwners = newsize;
}
}
hashcode = locallock->hashcode;
if (locallockp)
*locallockp = locallock;
/*
* If we already hold the lock, we can just increase the count locally.
*
* If lockCleared is already set, caller need not worry about absorbing
* sinval messages related to the lock's object.
*/
if (locallock->nLocks > 0)
{
GrantLockLocal(locallock, owner);
if (locallock->lockCleared)
return LOCKACQUIRE_ALREADY_CLEAR;
else
return LOCKACQUIRE_ALREADY_HELD;
}
/*
* lockHolder is the gang member that should hold and manage locks for this
* transaction. In Utility mode, or on the QD, it's always myself.
*
* On the QEs, it should normally be the Writer gang member.
*/
if (lockHolderProcPtr == NULL)
lockHolderProcPtr = MyProc;
if (lockmethodid == DEFAULT_LOCKMETHOD && locktag->locktag_type != LOCKTAG_TRANSACTION)
{
if (IS_QUERY_EXECUTOR_BACKEND() && !Gp_is_writer)
{
if (lockHolderProcPtr == MyProc)
{
/* Find the guy who should manage our locks */
PGPROC * proc = FindProcByGpSessionId(gp_session_id);
int count = 0;
while(proc==NULL && count < 5)
{
pg_usleep( /* microseconds */ 2000);
count++;
CHECK_FOR_INTERRUPTS();
proc = FindProcByGpSessionId(gp_session_id);
}
if (proc != NULL)
{
elog(DEBUG1,"Found writer proc entry. My Pid %d, his pid %d", MyProc-> pid, proc->pid);
lockHolderProcPtr = proc;
}
else
ereport(FATAL,
(errcode(ERRCODE_GP_INTERCONNECTION_ERROR),
errmsg(WRITER_IS_MISSING_MSG),
errdetail("lock [%u,%u] %s %d. "
"Probably because writer gang is gone somehow. "
"Maybe try rerunning.", locktag->locktag_field1,
locktag->locktag_field2, lock_mode_names[lockmode],
(int)locktag->locktag_type)));
}
}
}
/*
* Prepare to emit a WAL record if acquisition of this lock needs to be
* replayed in a standby server.
*
* Here we prepare to log; after lock is acquired we'll issue log record.
* This arrangement simplifies error recovery in case the preparation step
* fails.
*
* Only AccessExclusiveLocks can conflict with lock types that read-only
* transactions can acquire in a standby server. Make sure this definition
* matches the one in GetRunningTransactionLocks().
*/
if (lockmode >= AccessExclusiveLock &&
locktag->locktag_type == LOCKTAG_RELATION &&
!RecoveryInProgress() &&
XLogStandbyInfoActive())
{
LogAccessExclusiveLockPrepare();
log_lock = true;
}
/*
* Attempt to take lock via fast path, if eligible. But if we remember
* having filled up the fast path array, we don't attempt to make any
* further use of it until we release some locks. It's possible that some
* other backend has transferred some of those locks to the shared hash
* table, leaving space free, but it's not worth acquiring the LWLock just
* to check. It's also possible that we're acquiring a second or third
* lock type on a relation we have already locked using the fast-path, but
* for now we don't worry about that case either.
*/
if (EligibleForRelationFastPath(locktag, lockmode) &&
FastPathLocalUseCount < FP_LOCK_SLOTS_PER_BACKEND)
{
uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
bool acquired;
/*
* LWLockAcquire acts as a memory sequencing point, so it's safe to
* assume that any strong locker whose increment to
* FastPathStrongRelationLocks->counts becomes visible after we test
* it has yet to begin to transfer fast-path locks.
*/
LWLockAcquire(&MyProc->backendLock, LW_EXCLUSIVE);
if (FastPathStrongRelationLocks->count[fasthashcode] != 0)
acquired = false;
else
acquired = FastPathGrantRelationLock(locktag->locktag_field2,
lockmode);
LWLockRelease(&MyProc->backendLock);
if (acquired)
{
/*
* The locallock might contain stale pointers to some old shared
* objects; we MUST reset these to null before considering the
* lock to be acquired via fast-path.
*/
locallock->lock = NULL;
locallock->proclock = NULL;
GrantLockLocal(locallock, owner);
return LOCKACQUIRE_OK;
}
}
/*
* If this lock could potentially have been taken via the fast-path by
* some other backend, we must (temporarily) disable further use of the
* fast-path for this lock tag, and migrate any locks already taken via
* this method to the main lock table.
*/
if (ConflictsWithRelationFastPath(locktag, lockmode))
{
uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
BeginStrongLockAcquire(locallock, fasthashcode);
if (!FastPathTransferRelationLocks(lockMethodTable, locktag,
hashcode))
{
AbortStrongLockAcquire();
if (locallock->nLocks == 0)
RemoveLocalLock(locallock);
if (locallockp)
*locallockp = NULL;
if (reportMemoryError)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory"),
errhint("You might need to increase max_locks_per_transaction.")));
else
return LOCKACQUIRE_NOT_AVAIL;
}
}
/*
* We didn't find the lock in our LOCALLOCK table, and we didn't manage to
* take it via the fast-path, either, so we've got to mess with the shared
* lock table.
*/
partitionLock = LockHashPartitionLock(hashcode);
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
/*
* Find or create lock and proclock entries with this tag
*
* Note: if the locallock object already existed, it might have a pointer
* to the lock already ... but we should not assume that that pointer is
* valid, since a lock object with zero hold and request counts can go
* away anytime. So we have to use SetupLockInTable() to recompute the
* lock and proclock pointers, even if they're already set.
*/
proclock = SetupLockInTable(lockMethodTable, MyProc, locktag,
hashcode, lockmode);
if (!proclock)
{
AbortStrongLockAcquire();
LWLockRelease(partitionLock);
if (locallock->nLocks == 0)
RemoveLocalLock(locallock);
if (locallockp)
*locallockp = NULL;
if (reportMemoryError)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory"),
errhint("You might need to increase max_locks_per_transaction.")));
else
return LOCKACQUIRE_NOT_AVAIL;
}
locallock->proclock = proclock;
lock = proclock->tag.myLock;
locallock->lock = lock;
if (MyProc == lockHolderProcPtr)
{
/*
* We are a writer or utility mode connection. The following logic is
* identical to upstream PostgreSQL.
*/
/*
* If lock requested conflicts with locks requested by waiters, must join
* wait queue. Otherwise, check for conflict with already-held locks.
* (That's last because most complex check.)
*/
if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
status = STATUS_FOUND;
else
status = LockCheckConflicts(lockMethodTable, lockmode,
lock, proclock);
}
else
{
/*
* We are a reader, check waitMask conflict only if the writer doesn't
* hold this lock. We don't want a reader waiting for a lock that the
* writer is holding. This could lead to a deadlock. If writer
* doesn't hold the lock, waitMask conflict must be checked to avoid
* starvation of backends already waiting on the same lock.
*/
Assert(!Gp_is_writer);
PROCLOCKTAG writerProcLockTag;
uint32 writerProcLockHashCode;
writerProcLockTag.myLock = lock;
writerProcLockTag.myProc = lockHolderProcPtr;
writerProcLockHashCode = ProcLockHashCode(&writerProcLockTag, hashcode);
/*
* It is safe to access LockMethodProcLock hash table because
* partitionLock is already held at this point.
*/
Assert(LWLockHeldByMe(partitionLock));
PROCLOCK *writerProcLock = (PROCLOCK *)
hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &writerProcLockTag,
writerProcLockHashCode,
HASH_FIND,
&found);
if (found && writerProcLock->holdMask)
{
/* Writer holds the same lock, bypass waitMask check. */
status = LockCheckConflicts(lockMethodTable, lockmode,
lock, proclock);
}
else
{
/*
* Writer either hasn't requested this lock or is waiting on this
* lock. Checking for waitMask conflict is necessary to avoid
* starvation of existing waiters. Special case is conflict with
* awaiting writer's lockmode. Should the reader move ahead or
* continue to wait? It seems best to keep parity with behavior
* prior to this change, which is to let the reader wait.
*/
if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
status = STATUS_FOUND;
else
status = LockCheckConflicts(lockMethodTable, lockmode,
lock, proclock);
}
}
if (status == STATUS_OK)
{
if (MyProc != lockHolderProcPtr)
elog(DEBUG1, "Reader found lock %s on object %u/%u/%u doesn't conflict ",
lock_mode_names[lockmode],
lock->tag.locktag_field1, lock->tag.locktag_field2,
lock->tag.locktag_field3);
/* No conflict with held or previously requested locks */
GrantLock(lock, proclock, lockmode);
GrantLockLocal(locallock, owner);
}
else
{
Assert(status == STATUS_FOUND);
/*
* We can't acquire the lock immediately. If caller specified no
* blocking, remove useless table entries and return NOT_AVAIL without
* waiting.
*/
if (dontWait)
{
AbortStrongLockAcquire();
if (proclock->holdMask == 0)
{
uint32 proclock_hashcode;
proclock_hashcode = ProcLockHashCode(&proclock->tag, hashcode);
SHMQueueDelete(&proclock->lockLink);
SHMQueueDelete(&proclock->procLink);
if (!hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &(proclock->tag),
proclock_hashcode,
HASH_REMOVE,
NULL))
elog(PANIC, "proclock table corrupted");
}
else
PROCLOCK_PRINT("LockAcquire: NOWAIT", proclock);
lock->nRequested--;
lock->requested[lockmode]--;
LOCK_PRINT("LockAcquire: conditional lock failed", lock, lockmode);
Assert((lock->nRequested > 0) && (lock->requested[lockmode] >= 0));
Assert(lock->nGranted <= lock->nRequested);
LWLockRelease(partitionLock);
if (locallock->nLocks == 0)
RemoveLocalLock(locallock);
if (locallockp)
*locallockp = NULL;
return LOCKACQUIRE_NOT_AVAIL;
}
if (IS_QUERY_EXECUTOR_BACKEND())
{
if (!Gp_is_writer)
elog(LOG,"Reader gang member waiting on a lock [%u,%u] %s",
locktag->locktag_field1, locktag->locktag_field2,
lock_mode_names[lockmode]);
else
elog(DEBUG1,"Writer gang member waiting on a lock [%u,%u] %s",
locktag->locktag_field1, locktag->locktag_field2,
lock_mode_names[lockmode]);
}
/*
* Set bitmask of locks this process already holds on this object.
*/
MyProc->heldLocks = proclock->holdMask;
/*
* Sleep till someone wakes me up.
*/
TRACE_POSTGRESQL_LOCK_WAIT_START(locktag->locktag_field1,
locktag->locktag_field2,
locktag->locktag_field3,
locktag->locktag_field4,
locktag->locktag_type,
lockmode);
WaitOnLock(locallock, owner);
TRACE_POSTGRESQL_LOCK_WAIT_DONE(locktag->locktag_field1,
locktag->locktag_field2,
locktag->locktag_field3,
locktag->locktag_field4,
locktag->locktag_type,
lockmode);
/*
* NOTE: do not do any material change of state between here and
* return. All required changes in locktable state must have been
* done when the lock was granted to us --- see notes in WaitOnLock.
*/
/*
* Check the proclock entry status, in case something in the ipc
* communication doesn't work correctly.
*/
if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
{
AbortStrongLockAcquire();
PROCLOCK_PRINT("LockAcquire: INCONSISTENT", proclock);
LOCK_PRINT("LockAcquire: INCONSISTENT", lock, lockmode);
/* Should we retry ? */
LWLockRelease(partitionLock);
elog(ERROR, "LockAcquire failed");
}
PROCLOCK_PRINT("LockAcquire: granted", proclock);
LOCK_PRINT("LockAcquire: granted", lock, lockmode);
}
/*
* Lock state is fully up-to-date now; if we error out after this, no
* special error cleanup is required.
*/
FinishStrongLockAcquire();
LWLockRelease(partitionLock);
/*
* Emit a WAL record if acquisition of this lock needs to be replayed in a
* standby server.
*/
if (log_lock)
{
/*
* Decode the locktag back to the original values, to avoid sending
* lots of empty bytes with every message. See lock.h to check how a
* locktag is defined for LOCKTAG_RELATION
*/
LogAccessExclusiveLock(locktag->locktag_field1,
locktag->locktag_field2);
}
return LOCKACQUIRE_OK;
}
/*
* Find or create LOCK and PROCLOCK objects as needed for a new lock
* request.
*
* Returns the PROCLOCK object, or NULL if we failed to create the objects
* for lack of shared memory.
*
* The appropriate partition lock must be held at entry, and will be
* held at exit.
*/
static PROCLOCK *
SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc,
const LOCKTAG *locktag, uint32 hashcode, LOCKMODE lockmode)
{
LOCK *lock;
PROCLOCK *proclock;
PROCLOCKTAG proclocktag;
uint32 proclock_hashcode;
bool found;
/*
* Find or create a lock with this tag.
*/
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(const void *) locktag,
hashcode,
HASH_ENTER_NULL,
&found);
if (!lock)
return NULL;
/*
* if it's a new lock object, initialize it
*/
if (!found)
{
lock->grantMask = 0;
lock->waitMask = 0;
SHMQueueInit(&(lock->procLocks));
ProcQueueInit(&(lock->waitProcs));
lock->nRequested = 0;
lock->nGranted = 0;
MemSet(lock->requested, 0, sizeof(int) * MAX_LOCKMODES);
MemSet(lock->granted, 0, sizeof(int) * MAX_LOCKMODES);
/*
* By default, holdTillEndXact is true only for LOCKTAG_TRANSACTION
*/
lock->holdTillEndXact = locktag->locktag_type == LOCKTAG_TRANSACTION;
LOCK_PRINT("LockAcquire: new", lock, lockmode);
}
else
{
LOCK_PRINT("LockAcquire: found", lock, lockmode);
Assert((lock->nRequested >= 0) && (lock->requested[lockmode] >= 0));
Assert((lock->nGranted >= 0) && (lock->granted[lockmode] >= 0));
Assert(lock->nGranted <= lock->nRequested);
}
/*
* holdTillEndXact must be true for LOCKTAG_TRANSACTION and
* false for LOCKTAG_RELATION_EXTEND no matter if it is a new lock or
* an existing lock
*/
AssertImply(locktag->locktag_type == LOCKTAG_TRANSACTION,
lock->holdTillEndXact);
AssertImply(locktag->locktag_type == LOCKTAG_RELATION_EXTEND,
!(lock->holdTillEndXact));
/*
* Create the hash key for the proclock table.
*/
proclocktag.myLock = lock;
proclocktag.myProc = proc;
proclock_hashcode = ProcLockHashCode(&proclocktag, hashcode);
/*
* Find or create a proclock entry with this tag
*/
proclock = (PROCLOCK *) hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &proclocktag,
proclock_hashcode,
HASH_ENTER_NULL,
&found);
if (!proclock)
{
/* Oops, not enough shmem for the proclock */
if (lock->nRequested == 0)
{
/*
* There are no other requestors of this lock, so garbage-collect
* the lock object. We *must* do this to avoid a permanent leak
* of shared memory, because there won't be anything to cause
* anyone to release the lock object later.
*/
Assert(SHMQueueEmpty(&(lock->procLocks)));
if (!hash_search_with_hash_value(LockMethodLockHash,
(void *) &(lock->tag),
hashcode,
HASH_REMOVE,
NULL))
elog(PANIC, "lock table corrupted");
}
return NULL;
}
/*
* If new, initialize the new entry
*/
if (!found)
{
uint32 partition = LockHashPartition(hashcode);
/*
* It might seem unsafe to access proclock->groupLeader without a
* lock, but it's not really. Either we are initializing a proclock
* on our own behalf, in which case our group leader isn't changing
* because the group leader for a process can only ever be changed by
* the process itself; or else we are transferring a fast-path lock to
* the main lock table, in which case that process can't change it's
* lock group leader without first releasing all of its locks (and in
* particular the one we are currently transferring).
*/
proclock->groupLeader = proc->lockGroupLeader != NULL ?
proc->lockGroupLeader : proc;
proclock->holdMask = 0;
proclock->releaseMask = 0;
/* Add proclock to appropriate lists */
SHMQueueInsertBefore(&lock->procLocks, &proclock->lockLink);
SHMQueueInsertBefore(&(proc->myProcLocks[partition]),
&proclock->procLink);
PROCLOCK_PRINT("LockAcquire: new", proclock);
}
else
{
PROCLOCK_PRINT("LockAcquire: found", proclock);
Assert((proclock->holdMask & ~lock->grantMask) == 0);
#ifdef CHECK_DEADLOCK_RISK
/*
* Issue warning if we already hold a lower-level lock on this object
* and do not hold a lock of the requested level or higher. This
* indicates a deadlock-prone coding practice (eg, we'd have a
* deadlock if another backend were following the same code path at
* about the same time).
*
* This is not enabled by default, because it may generate log entries
* about user-level coding practices that are in fact safe in context.
* It can be enabled to help find system-level problems.
*
* XXX Doing numeric comparison on the lockmodes is a hack; it'd be
* better to use a table. For now, though, this works.
*/
{
int i;
for (i = lockMethodTable->numLockModes; i > 0; i--)
{
if (proclock->holdMask & LOCKBIT_ON(i))
{
if (i >= (int) lockmode)
break; /* safe: we have a lock >= req level */
elog(LOG, "deadlock risk: raising lock level"
" from %s to %s on object %u/%u/%u",
lockMethodTable->lockModeNames[i],
lockMethodTable->lockModeNames[lockmode],
lock->tag.locktag_field1, lock->tag.locktag_field2,
lock->tag.locktag_field3);
break;
}
}
}
#endif /* CHECK_DEADLOCK_RISK */
}
/*
* lock->nRequested and lock->requested[] count the total number of
* requests, whether granted or waiting, so increment those immediately.
* The other counts don't increment till we get the lock.
*/
lock->nRequested++;
lock->requested[lockmode]++;
Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
/*
* We shouldn't already hold the desired lock; else locallock table is
* broken.
*/
if (proclock->holdMask & LOCKBIT_ON(lockmode))
elog(ERROR, "lock %s on object %u/%u/%u is already held",
lockMethodTable->lockModeNames[lockmode],
lock->tag.locktag_field1, lock->tag.locktag_field2,
lock->tag.locktag_field3);
return proclock;
}
/*
* Subroutine to free a locallock entry
*/
void
RemoveLocalLock(LOCALLOCK *locallock)
{
int i;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (locallock->lockOwners[i].owner != NULL)
ResourceOwnerForgetLock(locallock->lockOwners[i].owner, locallock);
}
locallock->numLockOwners = 0;
if (locallock->lockOwners != NULL)
pfree(locallock->lockOwners);
locallock->lockOwners = NULL;
if (locallock->holdsStrongLockCount)
{
uint32 fasthashcode;
fasthashcode = FastPathStrongLockHashPartition(locallock->hashcode);
SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
FastPathStrongRelationLocks->count[fasthashcode]--;
locallock->holdsStrongLockCount = false;
SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
if (!hash_search(LockMethodLocalHash,
(void *) &(locallock->tag),
HASH_REMOVE, NULL))
elog(WARNING, "locallock table corrupted");
}
/*
* LockCheckConflicts -- test whether requested lock conflicts
* with those already granted
*
* Returns STATUS_FOUND if conflict, STATUS_OK if no conflict.
*
* NOTES:
* Here's what makes this complicated: one process's locks don't
* conflict with one another, no matter what purpose they are held for
* (eg, session and transaction locks do not conflict). Nor do the locks
* of one process in a lock group conflict with those of another process in
* the same group. So, we must subtract off these locks when determining
* whether the requested new lock conflicts with those already held.
*
* In Greenplum Database, the conflict is more complicated; not only the
* process itself but also other processes within the same MPP session may
* have held conflicting locks. We must take into consideration
* those MPP session member processes to subtract off the lock mask.
*/
int
LockCheckConflicts(LockMethod lockMethodTable,
LOCKMODE lockmode,
LOCK *lock,
PROCLOCK *proclock)
{
int numLockModes = lockMethodTable->numLockModes;
LOCKMASK myLocks;
int conflictMask = lockMethodTable->conflictTab[lockmode];
int conflictsRemaining[MAX_LOCKMODES];
int totalConflictsRemaining = 0;
int i;
SHM_QUEUE *procLocks;
PROCLOCK *otherproclock;
//MPP specific used variable
LOCKMASK otherLocks;
int mppSessionId;
/*
* first check for global conflicts: If no locks conflict with my request,
* then I get the lock.
*
* Checking for conflict: lock->grantMask represents the types of
* currently held locks. conflictTable[lockmode] has a bit set for each
* type of lock that conflicts with request. Bitwise compare tells if
* there is a conflict.
*/
if (!(conflictMask & lock->grantMask))
{
PROCLOCK_PRINT("LockCheckConflicts: no conflict", proclock);
return STATUS_OK;
}
/*
* GPDB_96_MERGE_FIXME:
* We do not support parallel execution yet, so it is fine to just
* handle mpp session and single process separately.
*
* After parallel execution feature is in, mpp session part should
* change.
*/
mppSessionId = proclock->tag.myProc->mppSessionId;
if (mppSessionId == InvalidGpSessionId)
{
/*
* Rats. Something conflicts. But it could still be my own lock, or a
* lock held by another member of my locking group. First, figure out how
* many conflicts remain after subtracting out any locks I hold myself.
*/
myLocks = proclock->holdMask;
for (i = 1; i <= numLockModes; i++)
{
if ((conflictMask & LOCKBIT_ON(i)) == 0)
{
conflictsRemaining[i] = 0;
continue;
}
conflictsRemaining[i] = lock->granted[i];
if (myLocks & LOCKBIT_ON(i))
--conflictsRemaining[i];
totalConflictsRemaining += conflictsRemaining[i];
}
/* If no conflicts remain, we get the lock. */
if (totalConflictsRemaining == 0)
{
PROCLOCK_PRINT("LockCheckConflicts: resolved (simple)", proclock);
return STATUS_OK;
}
/* If no group locking, it's definitely a conflict. */
if (proclock->groupLeader == MyProc && MyProc->lockGroupLeader == NULL)
{
Assert(proclock->tag.myProc == MyProc);
PROCLOCK_PRINT("LockCheckConflicts: conflicting (simple)",
proclock);
return STATUS_FOUND;
}
/*
* Locks held in conflicting modes by members of our own lock group are
* not real conflicts; we can subtract those out and see if we still have
* a conflict. This is O(N) in the number of processes holding or
* awaiting locks on this object. We could improve that by making the
* shared memory state more complex (and larger) but it doesn't seem worth
* it.
*/
procLocks = &(lock->procLocks);
otherproclock = (PROCLOCK *)
SHMQueueNext(procLocks, procLocks, offsetof(PROCLOCK, lockLink));
while (otherproclock != NULL)
{
if (proclock != otherproclock &&
proclock->groupLeader == otherproclock->groupLeader &&
(otherproclock->holdMask & conflictMask) != 0)
{
int intersectMask = otherproclock->holdMask & conflictMask;
for (i = 1; i <= numLockModes; i++)
{
if ((intersectMask & LOCKBIT_ON(i)) != 0)
{
if (conflictsRemaining[i] <= 0)
elog(PANIC, "proclocks held do not match lock");
conflictsRemaining[i]--;
totalConflictsRemaining--;
}
}
if (totalConflictsRemaining == 0)
{
PROCLOCK_PRINT("LockCheckConflicts: resolved (group)",
proclock);
return STATUS_OK;
}
}
otherproclock = (PROCLOCK *)
SHMQueueNext(procLocks, &otherproclock->lockLink,
offsetof(PROCLOCK, lockLink));
}
/* Nope, it's a real conflict. */
PROCLOCK_PRINT("LockCheckConflicts: conflicting (group)", proclock);
}
else
{
/* in mpp session */
otherLocks = 0;
for (i = 1; i <= numLockModes; i++)
{
int ourHolding = 0;
SHM_QUEUE *procLocks = &(lock->procLocks);
PROCLOCK *otherProclock =
(PROCLOCK *) SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, lockLink));
/*
* Go through the proclock queue in the lock. otherProclock
* may be this process itself.
*/
while (otherProclock)
{
PGPROC *otherProc = otherProclock->tag.myProc;
/*
* If processes in my session are holding the lock, mask
* it out so that we won't be blocked by them.
*/
if (otherProc->mppSessionId == mppSessionId &&
otherProclock->holdMask & LOCKBIT_ON(i))
ourHolding++;
otherProclock =
(PROCLOCK *) SHMQueueNext(procLocks,
&otherProclock->lockLink,
offsetof(PROCLOCK, lockLink));
}
/*
* I'll be blocked only if processes outside of the session are
* holding conflicting locks.
*/
if (lock->granted[i] > ourHolding)
otherLocks |= LOCKBIT_ON(i);
}
/*
* now check again for conflicts. 'otherLocks' describes the types of
* locks held by other sessions. If one of these conflicts with the kind
* of lock that I want, there is a conflict and I have to sleep.
*/
if (!(lockMethodTable->conflictTab[lockmode] & otherLocks))
{
/* no conflict. OK to get the lock */
PROCLOCK_PRINT("LockCheckConflicts: resolved", proclock);
return STATUS_OK;
}
PROCLOCK_PRINT("LockCheckConflicts: conflicting", proclock);
}
return STATUS_FOUND;
}
/*
* GrantLock -- update the lock and proclock data structures to show
* the lock request has been granted.
*
* NOTE: if proc was blocked, it also needs to be removed from the wait list
* and have its waitLock/waitProcLock fields cleared. That's not done here.
*
* NOTE: the lock grant also has to be recorded in the associated LOCALLOCK
* table entry; but since we may be awaking some other process, we can't do
* that here; it's done by GrantLockLocal, instead.
*/
void
GrantLock(LOCK *lock, PROCLOCK *proclock, LOCKMODE lockmode)
{
lock->nGranted++;
lock->granted[lockmode]++;
lock->grantMask |= LOCKBIT_ON(lockmode);
if (lock->granted[lockmode] == lock->requested[lockmode])
lock->waitMask &= LOCKBIT_OFF(lockmode);
proclock->holdMask |= LOCKBIT_ON(lockmode);
LOCK_PRINT("GrantLock", lock, lockmode);
Assert((lock->nGranted > 0) && (lock->granted[lockmode] > 0));
Assert(lock->nGranted <= lock->nRequested);
}
/*
* UnGrantLock -- opposite of GrantLock.
*
* Updates the lock and proclock data structures to show that the lock
* is no longer held nor requested by the current holder.
*
* Returns true if there were any waiters waiting on the lock that
* should now be woken up with ProcLockWakeup.
*/
static bool
UnGrantLock(LOCK *lock, LOCKMODE lockmode,
PROCLOCK *proclock, LockMethod lockMethodTable)
{
bool wakeupNeeded = false;
Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
Assert((lock->nGranted > 0) && (lock->granted[lockmode] > 0));
Assert(lock->nGranted <= lock->nRequested);
/*
* fix the general lock stats
*/
lock->nRequested--;
lock->requested[lockmode]--;
lock->nGranted--;
lock->granted[lockmode]--;
if (lock->granted[lockmode] == 0)
{
/* change the conflict mask. No more of this lock type. */
lock->grantMask &= LOCKBIT_OFF(lockmode);
}
LOCK_PRINT("UnGrantLock: updated", lock, lockmode);
/*
* We need only run ProcLockWakeup if the released lock conflicts with at
* least one of the lock types requested by waiter(s). Otherwise whatever
* conflict made them wait must still exist. NOTE: before MVCC, we could
* skip wakeup if lock->granted[lockmode] was still positive. But that's
* not true anymore, because the remaining granted locks might belong to
* some waiter, who could now be awakened because he doesn't conflict with
* his own locks.
*/
if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
wakeupNeeded = true;
/*
* Now fix the per-proclock state.
*/
proclock->holdMask &= LOCKBIT_OFF(lockmode);
PROCLOCK_PRINT("UnGrantLock: updated", proclock);
return wakeupNeeded;
}
/*
* CleanUpLock -- clean up after releasing a lock. We garbage-collect the
* proclock and lock objects if possible, and call ProcLockWakeup if there
* are remaining requests and the caller says it's OK. (Normally, this
* should be called after UnGrantLock, and wakeupNeeded is the result from
* UnGrantLock.)
*
* The appropriate partition lock must be held at entry, and will be
* held at exit.
*/
static void
CleanUpLock(LOCK *lock, PROCLOCK *proclock,
LockMethod lockMethodTable, uint32 hashcode,
bool wakeupNeeded)
{
/*
* If this was my last hold on this lock, delete my entry in the proclock
* table.
*/
if (proclock->holdMask == 0)
{
uint32 proclock_hashcode;
PROCLOCK_PRINT("CleanUpLock: deleting", proclock);
SHMQueueDelete(&proclock->lockLink);
SHMQueueDelete(&proclock->procLink);
proclock_hashcode = ProcLockHashCode(&proclock->tag, hashcode);
if (!hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &(proclock->tag),
proclock_hashcode,
HASH_REMOVE,
NULL))
elog(PANIC, "proclock table corrupted");
}
if (lock->nRequested == 0)
{
/*
* The caller just released the last lock, so garbage-collect the lock
* object.
*/
LOCK_PRINT("CleanUpLock: deleting", lock, 0);
Assert(SHMQueueEmpty(&(lock->procLocks)));
if (!hash_search_with_hash_value(LockMethodLockHash,
(void *) &(lock->tag),
hashcode,
HASH_REMOVE,
NULL))
elog(PANIC, "lock table corrupted");
}
else if (wakeupNeeded)
{
/* There are waiters on this lock, so wake them up. */
ProcLockWakeup(lockMethodTable, lock);
}
}
/*
* GrantLockLocal -- update the locallock data structures to show
* the lock request has been granted.
*
* We expect that LockAcquire made sure there is room to add a new
* ResourceOwner entry.
*/
static void
GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner)
{
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
int i;
Assert(locallock->numLockOwners < locallock->maxLockOwners);
/* Count the total */
locallock->nLocks++;
/* Count the per-owner lock */
for (i = 0; i < locallock->numLockOwners; i++)
{
if (lockOwners[i].owner == owner)
{
lockOwners[i].nLocks++;
return;
}
}
lockOwners[i].owner = owner;
lockOwners[i].nLocks = 1;
locallock->numLockOwners++;
if (owner != NULL)
ResourceOwnerRememberLock(owner, locallock);
}
/*
* BeginStrongLockAcquire - inhibit use of fastpath for a given LOCALLOCK,
* and arrange for error cleanup if it fails
*/
static void
BeginStrongLockAcquire(LOCALLOCK *locallock, uint32 fasthashcode)
{
Assert(StrongLockInProgress == NULL);
Assert(locallock->holdsStrongLockCount == false);
/*
* Adding to a memory location is not atomic, so we take a spinlock to
* ensure we don't collide with someone else trying to bump the count at
* the same time.
*
* XXX: It might be worth considering using an atomic fetch-and-add
* instruction here, on architectures where that is supported.
*/
SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
FastPathStrongRelationLocks->count[fasthashcode]++;
locallock->holdsStrongLockCount = true;
StrongLockInProgress = locallock;
SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
/*
* FinishStrongLockAcquire - cancel pending cleanup for a strong lock
* acquisition once it's no longer needed
*/
static void
FinishStrongLockAcquire(void)
{
StrongLockInProgress = NULL;
}
/*
* AbortStrongLockAcquire - undo strong lock state changes performed by
* BeginStrongLockAcquire.
*/
void
AbortStrongLockAcquire(void)
{
uint32 fasthashcode;
LOCALLOCK *locallock = StrongLockInProgress;
if (locallock == NULL)
return;
fasthashcode = FastPathStrongLockHashPartition(locallock->hashcode);
Assert(locallock->holdsStrongLockCount == true);
SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
FastPathStrongRelationLocks->count[fasthashcode]--;
locallock->holdsStrongLockCount = false;
StrongLockInProgress = NULL;
SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
/*
* GrantAwaitedLock -- call GrantLockLocal for the lock we are doing
* WaitOnLock on.
*
* proc.c needs this for the case where we are booted off the lock by
* timeout, but discover that someone granted us the lock anyway.
*
* We could just export GrantLockLocal, but that would require including
* resowner.h in lock.h, which creates circularity.
*/
void
GrantAwaitedLock(void)
{
GrantLockLocal(awaitedLock, awaitedOwner);
}
/*
* MarkLockClear -- mark an acquired lock as "clear"
*
* This means that we know we have absorbed all sinval messages that other
* sessions generated before we acquired this lock, and so we can confidently
* assume we know about any catalog changes protected by this lock.
*/
void
MarkLockClear(LOCALLOCK *locallock)
{
Assert(locallock->nLocks > 0);
locallock->lockCleared = true;
}
/*
* WaitOnLock -- wait to acquire a lock
*
* Caller must have set MyProc->heldLocks to reflect locks already held
* on the lockable object by this process.
*
* The appropriate partition lock must be held at entry.
*/
static void
WaitOnLock(LOCALLOCK *locallock, ResourceOwner owner)
{
LOCKMETHODID lockmethodid = LOCALLOCK_LOCKMETHOD(*locallock);
LockMethod lockMethodTable = LockMethods[lockmethodid];
char *volatile new_status = NULL;
LOCK_PRINT("WaitOnLock: sleeping on lock",
locallock->lock, locallock->tag.mode);
/* Report change to waiting status */
if (update_process_title)
{
const char *old_status;
int len;
old_status = get_real_act_ps_display(&len);
new_status = (char *) palloc(len + 8 + 1);
memcpy(new_status, old_status, len);
strcpy(new_status + len, " waiting");
set_ps_display(new_status, false);
new_status[len] = '\0'; /* truncate off " waiting" */
}
awaitedLock = locallock;
awaitedOwner = owner;
/*
* NOTE: Think not to put any shared-state cleanup after the call to
* ProcSleep, in either the normal or failure path. The lock state must
* be fully set by the lock grantor, or by CheckDeadLock if we give up
* waiting for the lock. This is necessary because of the possibility
* that a cancel/die interrupt will interrupt ProcSleep after someone else
* grants us the lock, but before we've noticed it. Hence, after granting,
* the locktable state must fully reflect the fact that we own the lock;
* we can't do additional work on return.
*
* We can and do use a PG_TRY block to try to clean up after failure, but
* this still has a major limitation: elog(FATAL) can occur while waiting
* (eg, a "die" interrupt), and then control won't come back here. So all
* cleanup of essential state should happen in LockErrorCleanup, not here.
* We can use PG_TRY to clear the "waiting" status flags, since doing that
* is unimportant if the process exits.
*/
PG_TRY();
{
if (ProcSleep(locallock, lockMethodTable) != STATUS_OK)
{
/*
* We failed as a result of a deadlock, see CheckDeadLock(). Quit
* now.
*/
awaitedLock = NULL;
LOCK_PRINT("WaitOnLock: aborting on lock",
locallock->lock, locallock->tag.mode);
LWLockRelease(LockHashPartitionLock(locallock->hashcode));
/*
* Now that we aren't holding the partition lock, we can give an
* error report including details about the detected deadlock.
*/
DeadLockReport();
/* not reached */
}
}
PG_CATCH();
{
/* In this path, awaitedLock remains set until LockErrorCleanup */
/* Report change to non-waiting status */
if (update_process_title)
{
set_ps_display(new_status, false);
pfree(new_status);
}
/* and propagate the error */
PG_RE_THROW();
}
PG_END_TRY();
awaitedLock = NULL;
/* Report change to non-waiting status */
if (update_process_title)
{
set_ps_display(new_status, false);
pfree(new_status);
}
LOCK_PRINT("WaitOnLock: wakeup on lock",
locallock->lock, locallock->tag.mode);
}
/*
* Remove a proc from the wait-queue it is on (caller must know it is on one).
* This is only used when the proc has failed to get the lock, so we set its
* waitStatus to STATUS_ERROR.
*
* Appropriate partition lock must be held by caller. Also, caller is
* responsible for signaling the proc if needed.
*
* NB: this does not clean up any locallock object that may exist for the lock.
*/
void
RemoveFromWaitQueue(PGPROC *proc, uint32 hashcode)
{
LOCK *waitLock = proc->waitLock;
PROCLOCK *proclock = proc->waitProcLock;
LOCKMODE lockmode = proc->waitLockMode;
LOCKMETHODID lockmethodid = LOCK_LOCKMETHOD(*waitLock);
/* Make lockmethod is appropriate. */
Assert(lockmethodid != RESOURCE_LOCKMETHOD);
/* Make sure proc is waiting */
Assert(proc->waitStatus == STATUS_WAITING);
Assert(proc->links.next != NULL);
Assert(waitLock);
Assert(waitLock->waitProcs.size > 0);
Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
/* Remove proc from lock's wait queue */
SHMQueueDelete(&(proc->links));
waitLock->waitProcs.size--;
/* Undo increments of request counts by waiting process */
Assert(waitLock->nRequested > 0);
Assert(waitLock->nRequested > proc->waitLock->nGranted);
waitLock->nRequested--;
Assert(waitLock->requested[lockmode] > 0);
waitLock->requested[lockmode]--;
/* don't forget to clear waitMask bit if appropriate */
if (waitLock->granted[lockmode] == waitLock->requested[lockmode])
waitLock->waitMask &= LOCKBIT_OFF(lockmode);
/* Clean up the proc's own state, and pass it the ok/fail signal */
proc->waitLock = NULL;
proc->waitProcLock = NULL;
proc->waitStatus = STATUS_ERROR;
/*
* Delete the proclock immediately if it represents no already-held locks.
* (This must happen now because if the owner of the lock decides to
* release it, and the requested/granted counts then go to zero,
* LockRelease expects there to be no remaining proclocks.) Then see if
* any other waiters for the lock can be woken up now.
*/
CleanUpLock(waitLock, proclock,
LockMethods[lockmethodid], hashcode,
true);
}
/*
* LockRelease -- look up 'locktag' and release one 'lockmode' lock on it.
* Release a session lock if 'sessionLock' is true, else release a
* regular transaction lock.
*
* Side Effects: find any waiting processes that are now wakable,
* grant them their requested locks and awaken them.
* (We have to grant the lock here to avoid a race between
* the waking process and any new process to
* come along and request the lock.)
*/
bool
LockRelease(const LOCKTAG *locktag, LOCKMODE lockmode, bool sessionLock)
{
LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
LockMethod lockMethodTable;
LOCALLOCKTAG localtag;
LOCALLOCK *locallock;
LOCK *lock;
PROCLOCK *proclock;
LWLock *partitionLock;
bool wakeupNeeded;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
elog(ERROR, "unrecognized lock mode: %d", lockmode);
#ifdef LOCK_DEBUG
if (LOCK_DEBUG_ENABLED(locktag))
elog(LOG, "LockRelease: lock [%u,%u] %s",
locktag->locktag_field1, locktag->locktag_field2,
lockMethodTable->lockModeNames[lockmode]);
#endif
/*
* Find the LOCALLOCK entry for this lock and lockmode
*/
MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
localtag.lock = *locktag;
localtag.mode = lockmode;
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
(void *) &localtag,
HASH_FIND, NULL);
/*
* let the caller print its own error message, too. Do not ereport(ERROR).
*/
if (!locallock || locallock->nLocks <= 0)
{
elog(WARNING, "you don't own a lock of type %s",
lockMethodTable->lockModeNames[lockmode]);
return false;
}
/*
* Decrease the count for the resource owner.
*/
{
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
ResourceOwner owner;
int i;
/* Identify owner for lock */
if (sessionLock)
owner = NULL;
else
owner = CurrentResourceOwner;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (lockOwners[i].owner == owner)
{
Assert(lockOwners[i].nLocks > 0);
if (--lockOwners[i].nLocks == 0)
{
if (owner != NULL)
ResourceOwnerForgetLock(owner, locallock);
/* compact out unused slot */
locallock->numLockOwners--;
if (i < locallock->numLockOwners)
lockOwners[i] = lockOwners[locallock->numLockOwners];
}
break;
}
}
if (i < 0)
{
/* don't release a lock belonging to another owner */
elog(WARNING, "you don't own a lock of type %s",
lockMethodTable->lockModeNames[lockmode]);
return false;
}
}
/*
* Decrease the total local count. If we're still holding the lock, we're
* done.
*/
locallock->nLocks--;
if (locallock->nLocks > 0)
return true;
/*
* At this point we can no longer suppose we are clear of invalidation
* messages related to this lock. Although we'll delete the LOCALLOCK
* object before any intentional return from this routine, it seems worth
* the trouble to explicitly reset lockCleared right now, just in case
* some error prevents us from deleting the LOCALLOCK.
*/
locallock->lockCleared = false;
/*
* At this point we can no longer suppose we are clear of invalidation
* messages related to this lock. Although we'll delete the LOCALLOCK
* object before any intentional return from this routine, it seems worth
* the trouble to explicitly reset lockCleared right now, just in case
* some error prevents us from deleting the LOCALLOCK.
*/
locallock->lockCleared = false;
/* Attempt fast release of any lock eligible for the fast path. */
if (EligibleForRelationFastPath(locktag, lockmode) &&
FastPathLocalUseCount > 0)
{
bool released;
/*
* We might not find the lock here, even if we originally entered it
* here. Another backend may have moved it to the main table.
*/
LWLockAcquire(&MyProc->backendLock, LW_EXCLUSIVE);
released = FastPathUnGrantRelationLock(locktag->locktag_field2,
lockmode);
LWLockRelease(&MyProc->backendLock);
if (released)
{
RemoveLocalLock(locallock);
return true;
}
}
/*
* Otherwise we've got to mess with the shared lock table.
*/
partitionLock = LockHashPartitionLock(locallock->hashcode);
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
/*
* Normally, we don't need to re-find the lock or proclock, since we kept
* their addresses in the locallock table, and they couldn't have been
* removed while we were holding a lock on them. But it's possible that
* the lock was taken fast-path and has since been moved to the main hash
* table by another backend, in which case we will need to look up the
* objects here. We assume the lock field is NULL if so.
*/
lock = locallock->lock;
if (!lock)
{
PROCLOCKTAG proclocktag;
Assert(EligibleForRelationFastPath(locktag, lockmode));
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(const void *) locktag,
locallock->hashcode,
HASH_FIND,
NULL);
if (!lock)
elog(ERROR, "failed to re-find shared lock object");
locallock->lock = lock;
proclocktag.myLock = lock;
proclocktag.myProc = MyProc;
locallock->proclock = (PROCLOCK *) hash_search(LockMethodProcLockHash,
(void *) &proclocktag,
HASH_FIND,
NULL);
if (!locallock->proclock)
elog(ERROR, "failed to re-find shared proclock object");
}
LOCK_PRINT("LockRelease: found", lock, lockmode);
proclock = locallock->proclock;
PROCLOCK_PRINT("LockRelease: found", proclock);
/*
* Double-check that we are actually holding a lock of the type we want to
* release.
*/
if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
{
PROCLOCK_PRINT("LockRelease: WRONGTYPE", proclock);
LWLockRelease(partitionLock);
elog(WARNING, "you don't own a lock of type %s",
lockMethodTable->lockModeNames[lockmode]);
RemoveLocalLock(locallock);
return false;
}
/*
* There are 3 possibilities for holdTillEndXact:
* 1. must be true for LOCKTAG_TRANSACTION
* 2. might be true or false for LOCKTAG_RELATION
* 3. must be false for others
*/
if(locktag->locktag_type == LOCKTAG_TRANSACTION)
{
/* must be true */
Assert(lock->holdTillEndXact);
}
else if(locktag->locktag_type == LOCKTAG_RELATION)
{
/* might be true or false, no assert */
}
else
{
/* must be false for others */
Assert(!(lock->holdTillEndXact));
}
/*
* Do the releasing. CleanUpLock will waken any now-wakable waiters.
*/
wakeupNeeded = UnGrantLock(lock, lockmode, proclock, lockMethodTable);
CleanUpLock(lock, proclock,
lockMethodTable, locallock->hashcode,
wakeupNeeded);
LWLockRelease(partitionLock);
RemoveLocalLock(locallock);
return true;
}
void
LockSetHoldTillEndXact(const LOCKTAG *locktag)
{
LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
LockMethod lockMethodTable;
LOCALLOCKTAG localtag;
LOCALLOCK *locallock;
LOCKMODE lm;
Oid relid;
/*
* A relation lock would exist either in fast-pach or in shared lock
* table. So we could return immediately if we have found it in fast-path.
*/
relid = locktag->locktag_field2;
if (setFPHoldTillEndXact(relid))
return;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
for (lm = 1; lm <= lockMethodTable->numLockModes; lm++)
{
#ifdef LOCK_DEBUG
if (LOCK_DEBUG_ENABLED(locktag))
elog(LOG, "LockRelease: lock [%u,%u] %s",
locktag->locktag_field1, locktag->locktag_field2,
lockMethodTable->lockModeNames[lm]);
#endif
/*
* Find the LOCALLOCK entry for this lock and lockmode
*/
MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
localtag.lock = *locktag;
localtag.mode = lm;
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash,
(void *) &localtag,
HASH_FIND, NULL);
if (!locallock || locallock->nLocks <= 0)
continue;
if (locallock->lock)
locallock->lock->holdTillEndXact = true;
}
}
/*
* LockReleaseAll -- Release all locks of the specified lock method that
* are held by the current process.
*
* Well, not necessarily *all* locks. The available behaviors are:
* allLocks == true: release all locks including session locks.
* allLocks == false: release all non-session locks.
*/
void
LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks)
{
HASH_SEQ_STATUS status;
LockMethod lockMethodTable;
int i,
numLockModes;
LOCALLOCK *locallock;
LOCK *lock;
PROCLOCK *proclock;
int partition;
bool have_fast_path_lwlock = false;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
#ifdef LOCK_DEBUG
if (*(lockMethodTable->trace_flag))
elog(LOG, "LockReleaseAll: lockmethod=%d", lockmethodid);
#endif
/*
* Get rid of our fast-path VXID lock, if appropriate. Note that this is
* the only way that the lock we hold on our own VXID can ever get
* released: it is always and only released when a toplevel transaction
* ends.
*/
if (lockmethodid == DEFAULT_LOCKMETHOD)
VirtualXactLockTableCleanup();
numLockModes = lockMethodTable->numLockModes;
/*
* First we run through the locallock table and get rid of unwanted
* entries, then we scan the process's proclocks and get rid of those. We
* do this separately because we may have multiple locallock entries
* pointing to the same proclock, and we daren't end up with any dangling
* pointers. Fast-path locks are cleaned up during the locallock table
* scan, though.
*/
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
{
/*
* If the LOCALLOCK entry is unused, we must've run out of shared
* memory while trying to set up this lock. Just forget the local
* entry.
*/
if (locallock->nLocks == 0)
{
RemoveLocalLock(locallock);
continue;
}
/* Ignore items that are not of the lockmethod to be removed */
if (LOCALLOCK_LOCKMETHOD(*locallock) != lockmethodid)
continue;
/*
* If we are asked to release all locks, we can just zap the entry.
* Otherwise, must scan to see if there are session locks. We assume
* there is at most one lockOwners entry for session locks.
*/
if (!allLocks)
{
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
/* If session lock is above array position 0, move it down to 0 */
for (i = 0; i < locallock->numLockOwners; i++)
{
if (lockOwners[i].owner == NULL)
lockOwners[0] = lockOwners[i];
else
ResourceOwnerForgetLock(lockOwners[i].owner, locallock);
}
if (locallock->numLockOwners > 0 &&
lockOwners[0].owner == NULL &&
lockOwners[0].nLocks > 0)
{
/* Fix the locallock to show just the session locks */
locallock->nLocks = lockOwners[0].nLocks;
locallock->numLockOwners = 1;
/* We aren't deleting this locallock, so done */
continue;
}
else
locallock->numLockOwners = 0;
}
/*
* If the lock or proclock pointers are NULL, this lock was taken via
* the relation fast-path (and is not known to have been transferred).
*/
if (locallock->proclock == NULL || locallock->lock == NULL)
{
LOCKMODE lockmode = locallock->tag.mode;
Oid relid;
/* Verify that a fast-path lock is what we've got. */
if (!EligibleForRelationFastPath(&locallock->tag.lock, lockmode))
elog(PANIC, "locallock table corrupted");
/*
* If we don't currently hold the LWLock that protects our
* fast-path data structures, we must acquire it before attempting
* to release the lock via the fast-path. We will continue to
* hold the LWLock until we're done scanning the locallock table,
* unless we hit a transferred fast-path lock. (XXX is this
* really such a good idea? There could be a lot of entries ...)
*/
if (!have_fast_path_lwlock)
{
LWLockAcquire(&MyProc->backendLock, LW_EXCLUSIVE);
have_fast_path_lwlock = true;
}
/* Attempt fast-path release. */
relid = locallock->tag.lock.locktag_field2;
if (FastPathUnGrantRelationLock(relid, lockmode))
{
RemoveLocalLock(locallock);
continue;
}
/*
* Our lock, originally taken via the fast path, has been
* transferred to the main lock table. That's going to require
* some extra work, so release our fast-path lock before starting.
*/
LWLockRelease(&MyProc->backendLock);
have_fast_path_lwlock = false;
/*
* Now dump the lock. We haven't got a pointer to the LOCK or
* PROCLOCK in this case, so we have to handle this a bit
* differently than a normal lock release. Unfortunately, this
* requires an extra LWLock acquire-and-release cycle on the
* partitionLock, but hopefully it shouldn't happen often.
*/
LockRefindAndRelease(lockMethodTable, MyProc,
&locallock->tag.lock, lockmode, false);
RemoveLocalLock(locallock);
continue;
}
/* Mark the proclock to show we need to release this lockmode */
if (locallock->nLocks > 0)
locallock->proclock->releaseMask |= LOCKBIT_ON(locallock->tag.mode);
/* And remove the locallock hashtable entry */
RemoveLocalLock(locallock);
}
/* Done with the fast-path data structures */
if (have_fast_path_lwlock)
LWLockRelease(&MyProc->backendLock);
/*
* Now, scan each lock partition separately.
*/
for (partition = 0; partition < NUM_LOCK_PARTITIONS; partition++)
{
LWLock *partitionLock;
SHM_QUEUE *procLocks = &(MyProc->myProcLocks[partition]);
PROCLOCK *nextplock;
partitionLock = LockHashPartitionLockByIndex(partition);
/*
* If the proclock list for this partition is empty, we can skip
* acquiring the partition lock. This optimization is trickier than
* it looks, because another backend could be in process of adding
* something to our proclock list due to promoting one of our
* fast-path locks. However, any such lock must be one that we
* decided not to delete above, so it's okay to skip it again now;
* we'd just decide not to delete it again. We must, however, be
* careful to re-fetch the list header once we've acquired the
* partition lock, to be sure we have a valid, up-to-date pointer.
* (There is probably no significant risk if pointer fetch/store is
* atomic, but we don't wish to assume that.)
*
* XXX This argument assumes that the locallock table correctly
* represents all of our fast-path locks. While allLocks mode
* guarantees to clean up all of our normal locks regardless of the
* locallock situation, we lose that guarantee for fast-path locks.
* This is not ideal.
*/
if (SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, procLink)) == NULL)
continue; /* needn't examine this partition */
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
for (proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, procLink));
proclock;
proclock = nextplock)
{
bool wakeupNeeded = false;
/* Get link first, since we may unlink/delete this proclock */
nextplock = (PROCLOCK *)
SHMQueueNext(procLocks, &proclock->procLink,
offsetof(PROCLOCK, procLink));
Assert(proclock->tag.myProc == MyProc);
lock = proclock->tag.myLock;
/* Ignore items that are not of the lockmethod to be removed */
if (LOCK_LOCKMETHOD(*lock) != lockmethodid)
continue;
/*
* In allLocks mode, force release of all locks even if locallock
* table had problems
*/
if (allLocks)
proclock->releaseMask = proclock->holdMask;
else
Assert((proclock->releaseMask & ~proclock->holdMask) == 0);
/*
* Ignore items that have nothing to be released, unless they have
* holdMask == 0 and are therefore recyclable
*/
if (proclock->releaseMask == 0 && proclock->holdMask != 0)
continue;
PROCLOCK_PRINT("LockReleaseAll", proclock);
LOCK_PRINT("LockReleaseAll", lock, 0);
Assert(lock->nRequested >= 0);
Assert(lock->nGranted >= 0);
Assert(lock->nGranted <= lock->nRequested);
Assert((proclock->holdMask & ~lock->grantMask) == 0);
/*
* Release the previously-marked lock modes
*/
for (i = 1; i <= numLockModes; i++)
{
if (proclock->releaseMask & LOCKBIT_ON(i))
wakeupNeeded |= UnGrantLock(lock, i, proclock,
lockMethodTable);
}
Assert((lock->nRequested >= 0) && (lock->nGranted >= 0));
Assert(lock->nGranted <= lock->nRequested);
LOCK_PRINT("LockReleaseAll: updated", lock, 0);
proclock->releaseMask = 0;
/* CleanUpLock will wake up waiters if needed. */
CleanUpLock(lock, proclock,
lockMethodTable,
LockTagHashCode(&lock->tag),
wakeupNeeded);
} /* loop over PROCLOCKs within this partition */
LWLockRelease(partitionLock);
} /* loop over partitions */
#ifdef LOCK_DEBUG
if (*(lockMethodTable->trace_flag))
elog(LOG, "LockReleaseAll done");
#endif
}
/*
* LockReleaseSession -- Release all session locks of the specified lock method
* that are held by the current process.
*/
void
LockReleaseSession(LOCKMETHODID lockmethodid)
{
HASH_SEQ_STATUS status;
LOCALLOCK *locallock;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
{
/* Ignore items that are not of the specified lock method */
if (LOCALLOCK_LOCKMETHOD(*locallock) != lockmethodid)
continue;
ReleaseLockIfHeld(locallock, true);
}
}
/*
* LockReleaseCurrentOwner
* Release all locks belonging to CurrentResourceOwner
*
* If the caller knows what those locks are, it can pass them as an array.
* That speeds up the call significantly, when a lot of locks are held.
* Otherwise, pass NULL for locallocks, and we'll traverse through our hash
* table to find them.
*/
void
LockReleaseCurrentOwner(LOCALLOCK **locallocks, int nlocks)
{
if (locallocks == NULL)
{
HASH_SEQ_STATUS status;
LOCALLOCK *locallock;
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
ReleaseLockIfHeld(locallock, false);
}
else
{
int i;
for (i = nlocks - 1; i >= 0; i--)
ReleaseLockIfHeld(locallocks[i], false);
}
}
/*
* ReleaseLockIfHeld
* Release any session-level locks on this lockable object if sessionLock
* is true; else, release any locks held by CurrentResourceOwner.
*
* It is tempting to pass this a ResourceOwner pointer (or NULL for session
* locks), but without refactoring LockRelease() we cannot support releasing
* locks belonging to resource owners other than CurrentResourceOwner.
* If we were to refactor, it'd be a good idea to fix it so we don't have to
* do a hashtable lookup of the locallock, too. However, currently this
* function isn't used heavily enough to justify refactoring for its
* convenience.
*/
static void
ReleaseLockIfHeld(LOCALLOCK *locallock, bool sessionLock)
{
ResourceOwner owner;
LOCALLOCKOWNER *lockOwners;
int i;
/* Identify owner for lock (must match LockRelease!) */
if (sessionLock)
owner = NULL;
else
owner = CurrentResourceOwner;
/* Scan to see if there are any locks belonging to the target owner */
lockOwners = locallock->lockOwners;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (lockOwners[i].owner == owner)
{
Assert(lockOwners[i].nLocks > 0);
if (lockOwners[i].nLocks < locallock->nLocks)
{
/*
* We will still hold this lock after forgetting this
* ResourceOwner.
*/
locallock->nLocks -= lockOwners[i].nLocks;
/* compact out unused slot */
locallock->numLockOwners--;
if (owner != NULL)
ResourceOwnerForgetLock(owner, locallock);
if (i < locallock->numLockOwners)
lockOwners[i] = lockOwners[locallock->numLockOwners];
}
else
{
Assert(lockOwners[i].nLocks == locallock->nLocks);
/* We want to call LockRelease just once */
lockOwners[i].nLocks = 1;
locallock->nLocks = 1;
if (!LockRelease(&locallock->tag.lock,
locallock->tag.mode,
sessionLock))
elog(WARNING, "ReleaseLockIfHeld: failed??");
}
break;
}
}
}
/*
* LockReassignCurrentOwner
* Reassign all locks belonging to CurrentResourceOwner to belong
* to its parent resource owner.
*
* If the caller knows what those locks are, it can pass them as an array.
* That speeds up the call significantly, when a lot of locks are held
* (e.g pg_dump with a large schema). Otherwise, pass NULL for locallocks,
* and we'll traverse through our hash table to find them.
*/
void
LockReassignCurrentOwner(LOCALLOCK **locallocks, int nlocks)
{
ResourceOwner parent = ResourceOwnerGetParent(CurrentResourceOwner);
Assert(parent != NULL);
if (locallocks == NULL)
{
HASH_SEQ_STATUS status;
LOCALLOCK *locallock;
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
LockReassignOwner(locallock, parent);
}
else
{
int i;
for (i = nlocks - 1; i >= 0; i--)
LockReassignOwner(locallocks[i], parent);
}
}
/*
* Subroutine of LockReassignCurrentOwner. Reassigns a given lock belonging to
* CurrentResourceOwner to its parent.
*/
static void
LockReassignOwner(LOCALLOCK *locallock, ResourceOwner parent)
{
LOCALLOCKOWNER *lockOwners;
int i;
int ic = -1;
int ip = -1;
/*
* Scan to see if there are any locks belonging to current owner or its
* parent
*/
lockOwners = locallock->lockOwners;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (lockOwners[i].owner == CurrentResourceOwner)
ic = i;
else if (lockOwners[i].owner == parent)
ip = i;
}
if (ic < 0)
return; /* no current locks */
if (ip < 0)
{
/* Parent has no slot, so just give it the child's slot */
lockOwners[ic].owner = parent;
ResourceOwnerRememberLock(parent, locallock);
}
else
{
/* Merge child's count with parent's */
lockOwners[ip].nLocks += lockOwners[ic].nLocks;
/* compact out unused slot */
locallock->numLockOwners--;
if (ic < locallock->numLockOwners)
lockOwners[ic] = lockOwners[locallock->numLockOwners];
}
ResourceOwnerForgetLock(CurrentResourceOwner, locallock);
}
/*
* FastPathGrantRelationLock
* Grant lock using per-backend fast-path array, if there is space.
*/
static bool
FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode)
{
uint32 f;
uint32 unused_slot = FP_LOCK_SLOTS_PER_BACKEND;
/* Scan for existing entry for this relid, remembering empty slot. */
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
{
if (FAST_PATH_GET_BITS(MyProc, f) == 0)
unused_slot = f;
else if (MyProc->fpRelId[f] == relid)
{
Assert(!FAST_PATH_CHECK_LOCKMODE(MyProc, f, lockmode));
FAST_PATH_SET_LOCKMODE(MyProc, f, lockmode);
return true;
}
}
/* If no existing entry, use any empty slot. */
if (unused_slot < FP_LOCK_SLOTS_PER_BACKEND)
{
MyProc->fpRelId[unused_slot] = relid;
FAST_PATH_SET_HOLD_TILL_END_XACT(MyProc, unused_slot, 0);
FAST_PATH_SET_LOCKMODE(MyProc, unused_slot, lockmode);
++FastPathLocalUseCount;
return true;
}
/* No existing entry, and no empty slot. */
return false;
}
/*
* FastPathUnGrantRelationLock
* Release fast-path lock, if present. Update backend-private local
* use count, while we're at it.
*/
static bool
FastPathUnGrantRelationLock(Oid relid, LOCKMODE lockmode)
{
uint32 f;
bool result = false;
FastPathLocalUseCount = 0;
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
{
if (MyProc->fpRelId[f] == relid
&& FAST_PATH_CHECK_LOCKMODE(MyProc, f, lockmode))
{
Assert(!result);
FAST_PATH_CLEAR_LOCKMODE(MyProc, f, lockmode);
result = true;
/* we continue iterating so as to update FastPathLocalUseCount */
}
if (FAST_PATH_GET_BITS(MyProc, f) != 0)
++FastPathLocalUseCount;
}
return result;
}
/*
* FastPathTransferRelationLocks
* Transfer locks matching the given lock tag from per-backend fast-path
* arrays to the shared hash table.
*
* Returns true if successful, false if ran out of shared memory.
*/
static bool
FastPathTransferRelationLocks(LockMethod lockMethodTable, const LOCKTAG *locktag,
uint32 hashcode)
{
LWLock *partitionLock = LockHashPartitionLock(hashcode);
Oid relid = locktag->locktag_field2;
uint32 i;
/*
* Every PGPROC that can potentially hold a fast-path lock is present in
* ProcGlobal->allProcs. Prepared transactions are not, but any
* outstanding fast-path locks held by prepared transactions are
* transferred to the main lock table.
*/
for (i = 0; i < ProcGlobal->allProcCount; i++)
{
PGPROC *proc = &ProcGlobal->allProcs[i];
uint32 f;
LWLockAcquire(&proc->backendLock, LW_EXCLUSIVE);
/*
* If the target backend isn't referencing the same database as the
* lock, then we needn't examine the individual relation IDs at all;
* none of them can be relevant.
*
* proc->databaseId is set at backend startup time and never changes
* thereafter, so it might be safe to perform this test before
* acquiring &proc->backendLock. In particular, it's certainly safe
* to assume that if the target backend holds any fast-path locks, it
* must have performed a memory-fencing operation (in particular, an
* LWLock acquisition) since setting proc->databaseId. However, it's
* less clear that our backend is certain to have performed a memory
* fencing operation since the other backend set proc->databaseId. So
* for now, we test it after acquiring the LWLock just to be safe.
*/
if (proc->databaseId != locktag->locktag_field1)
{
LWLockRelease(&proc->backendLock);
continue;
}
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
{
uint32 lockmode;
/* Look for an allocated slot matching the given relid. */
if (relid != proc->fpRelId[f] || FAST_PATH_GET_BITS(proc, f) == 0)
continue;
/* Find or create lock object. */
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
for (lockmode = FAST_PATH_LOCKNUMBER_OFFSET;
lockmode < FAST_PATH_LOCKNUMBER_OFFSET + FAST_PATH_BITS_PER_SLOT;
++lockmode)
{
PROCLOCK *proclock;
if (!FAST_PATH_CHECK_LOCKMODE(proc, f, lockmode))
continue;
proclock = SetupLockInTable(lockMethodTable, proc, locktag,
hashcode, lockmode);
if (!proclock)
{
LWLockRelease(partitionLock);
LWLockRelease(&proc->backendLock);
return false;
}
/* Set holdTillEndXact of proclock */
proclock->tag.myLock->holdTillEndXact = \
FAST_PATH_GET_HOLD_TILL_END_XACT_BITS(proc, f) > 0;
GrantLock(proclock->tag.myLock, proclock, lockmode);
FAST_PATH_CLEAR_LOCKMODE(proc, f, lockmode);
}
LWLockRelease(partitionLock);
/* No need to examine remaining slots. */
break;
}
LWLockRelease(&proc->backendLock);
}
return true;
}
/*
* FastPathGetLockEntry
* Return the PROCLOCK for a lock originally taken via the fast-path,
* transferring it to the primary lock table if necessary.
*
* Note: caller takes care of updating the locallock object.
*/
static PROCLOCK *
FastPathGetRelationLockEntry(LOCALLOCK *locallock)
{
LockMethod lockMethodTable = LockMethods[DEFAULT_LOCKMETHOD];
LOCKTAG *locktag = &locallock->tag.lock;
PROCLOCK *proclock = NULL;
LWLock *partitionLock = LockHashPartitionLock(locallock->hashcode);
Oid relid = locktag->locktag_field2;
uint32 f;
LWLockAcquire(&MyProc->backendLock, LW_EXCLUSIVE);
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
{
uint32 lockmode;
/* Look for an allocated slot matching the given relid. */
if (relid != MyProc->fpRelId[f] || FAST_PATH_GET_BITS(MyProc, f) == 0)
continue;
/* If we don't have a lock of the given mode, forget it! */
lockmode = locallock->tag.mode;
if (!FAST_PATH_CHECK_LOCKMODE(MyProc, f, lockmode))
break;
/* Find or create lock object. */
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
proclock = SetupLockInTable(lockMethodTable, MyProc, locktag,
locallock->hashcode, lockmode);
if (!proclock)
{
LWLockRelease(partitionLock);
LWLockRelease(&MyProc->backendLock);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory"),
errhint("You might need to increase max_locks_per_transaction.")));
}
GrantLock(proclock->tag.myLock, proclock, lockmode);
FAST_PATH_CLEAR_LOCKMODE(MyProc, f, lockmode);
LWLockRelease(partitionLock);
/* No need to examine remaining slots. */
break;
}
LWLockRelease(&MyProc->backendLock);
/* Lock may have already been transferred by some other backend. */
if (proclock == NULL)
{
LOCK *lock;
PROCLOCKTAG proclocktag;
uint32 proclock_hashcode;
LWLockAcquire(partitionLock, LW_SHARED);
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(void *) locktag,
locallock->hashcode,
HASH_FIND,
NULL);
if (!lock)
elog(ERROR, "failed to re-find shared lock object");
proclocktag.myLock = lock;
proclocktag.myProc = MyProc;
proclock_hashcode = ProcLockHashCode(&proclocktag, locallock->hashcode);
proclock = (PROCLOCK *)
hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &proclocktag,
proclock_hashcode,
HASH_FIND,
NULL);
if (!proclock)
elog(ERROR, "failed to re-find shared proclock object");
LWLockRelease(partitionLock);
}
return proclock;
}
/*
* GetLockConflicts
* Get an array of VirtualTransactionIds of xacts currently holding locks
* that would conflict with the specified lock/lockmode.
* xacts merely awaiting such a lock are NOT reported.
*
* The result array is palloc'd and is terminated with an invalid VXID.
* *countp, if not null, is updated to the number of items set.
*
* Of course, the result could be out of date by the time it's returned,
* so use of this function has to be thought about carefully.
*
* Note we never include the current xact's vxid in the result array,
* since an xact never blocks itself. Also, prepared transactions are
* ignored, which is a bit more debatable but is appropriate for current
* uses of the result.
*/
VirtualTransactionId *
GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode, int *countp)
{
static VirtualTransactionId *vxids;
LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
LockMethod lockMethodTable;
LOCK *lock;
LOCKMASK conflictMask;
SHM_QUEUE *procLocks;
PROCLOCK *proclock;
uint32 hashcode;
LWLock *partitionLock;
int count = 0;
int fast_count = 0;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
if (lockmode <= 0 || lockmode > lockMethodTable->numLockModes)
elog(ERROR, "unrecognized lock mode: %d", lockmode);
/*
* Allocate memory to store results, and fill with InvalidVXID. We only
* need enough space for MaxBackends + a terminator, since prepared xacts
* don't count. InHotStandby allocate once in TopMemoryContext.
*/
if (InHotStandby)
{
if (vxids == NULL)
vxids = (VirtualTransactionId *)
MemoryContextAlloc(TopMemoryContext,
sizeof(VirtualTransactionId) * (MaxBackends + 1));
}
else
vxids = (VirtualTransactionId *)
palloc0(sizeof(VirtualTransactionId) * (MaxBackends + 1));
/* Compute hash code and partition lock, and look up conflicting modes. */
hashcode = LockTagHashCode(locktag);
partitionLock = LockHashPartitionLock(hashcode);
conflictMask = lockMethodTable->conflictTab[lockmode];
/*
* Fast path locks might not have been entered in the primary lock table.
* If the lock we're dealing with could conflict with such a lock, we must
* examine each backend's fast-path array for conflicts.
*/
if (ConflictsWithRelationFastPath(locktag, lockmode))
{
int i;
Oid relid = locktag->locktag_field2;
VirtualTransactionId vxid;
/*
* Iterate over relevant PGPROCs. Anything held by a prepared
* transaction will have been transferred to the primary lock table,
* so we need not worry about those. This is all a bit fuzzy, because
* new locks could be taken after we've visited a particular
* partition, but the callers had better be prepared to deal with that
* anyway, since the locks could equally well be taken between the
* time we return the value and the time the caller does something
* with it.
*/
for (i = 0; i < ProcGlobal->allProcCount; i++)
{
PGPROC *proc = &ProcGlobal->allProcs[i];
uint32 f;
/* A backend never blocks itself */
if (proc == MyProc)
continue;
LWLockAcquire(&proc->backendLock, LW_SHARED);
/*
* If the target backend isn't referencing the same database as
* the lock, then we needn't examine the individual relation IDs
* at all; none of them can be relevant.
*
* See FastPathTransferLocks() for discussion of why we do this
* test after acquiring the lock.
*/
if (proc->databaseId != locktag->locktag_field1)
{
LWLockRelease(&proc->backendLock);
continue;
}
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; f++)
{
uint32 lockmask;
/* Look for an allocated slot matching the given relid. */
if (relid != proc->fpRelId[f])
continue;
lockmask = FAST_PATH_GET_BITS(proc, f);
if (!lockmask)
continue;
lockmask <<= FAST_PATH_LOCKNUMBER_OFFSET;
/*
* There can only be one entry per relation, so if we found it
* and it doesn't conflict, we can skip the rest of the slots.
*/
if ((lockmask & conflictMask) == 0)
break;
/* Conflict! */
GET_VXID_FROM_PGPROC(vxid, *proc);
/*
* If we see an invalid VXID, then either the xact has already
* committed (or aborted), or it's a prepared xact. In either
* case we may ignore it.
*/
if (VirtualTransactionIdIsValid(vxid))
vxids[count++] = vxid;
/* No need to examine remaining slots. */
break;
}
LWLockRelease(&proc->backendLock);
}
}
/* Remember how many fast-path conflicts we found. */
fast_count = count;
/*
* Look up the lock object matching the tag.
*/
LWLockAcquire(partitionLock, LW_SHARED);
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(const void *) locktag,
hashcode,
HASH_FIND,
NULL);
if (!lock)
{
/*
* If the lock object doesn't exist, there is nothing holding a lock
* on this lockable object.
*/
LWLockRelease(partitionLock);
vxids[count].backendId = InvalidBackendId;
vxids[count].localTransactionId = InvalidLocalTransactionId;
if (countp)
*countp = count;
return vxids;
}
/*
* Examine each existing holder (or awaiter) of the lock.
*/
procLocks = &(lock->procLocks);
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, lockLink));
while (proclock)
{
if (conflictMask & proclock->holdMask)
{
PGPROC *proc = proclock->tag.myProc;
/* A backend never blocks itself */
if (proc != MyProc)
{
VirtualTransactionId vxid;
GET_VXID_FROM_PGPROC(vxid, *proc);
/*
* If we see an invalid VXID, then either the xact has already
* committed (or aborted), or it's a prepared xact. In either
* case we may ignore it.
*/
if (VirtualTransactionIdIsValid(vxid))
{
int i;
/* Avoid duplicate entries. */
for (i = 0; i < fast_count; ++i)
if (VirtualTransactionIdEquals(vxids[i], vxid))
break;
if (i >= fast_count)
vxids[count++] = vxid;
}
}
}
proclock = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->lockLink,
offsetof(PROCLOCK, lockLink));
}
LWLockRelease(partitionLock);
if (count > MaxBackends) /* should never happen */
elog(PANIC, "too many conflicting locks found");
vxids[count].backendId = InvalidBackendId;
vxids[count].localTransactionId = InvalidLocalTransactionId;
if (countp)
*countp = count;
return vxids;
}
/*
* Find a lock in the shared lock table and release it. It is the caller's
* responsibility to verify that this is a sane thing to do. (For example, it
* would be bad to release a lock here if there might still be a LOCALLOCK
* object with pointers to it.)
*
* We currently use this in two situations: first, to release locks held by
* prepared transactions on commit (see lock_twophase_postcommit); and second,
* to release locks taken via the fast-path, transferred to the main hash
* table, and then released (see LockReleaseAll).
*/
static void
LockRefindAndRelease(LockMethod lockMethodTable, PGPROC *proc,
LOCKTAG *locktag, LOCKMODE lockmode,
bool decrement_strong_lock_count)
{
LOCK *lock;
PROCLOCK *proclock;
PROCLOCKTAG proclocktag;
uint32 hashcode;
uint32 proclock_hashcode;
LWLock *partitionLock;
bool wakeupNeeded;
hashcode = LockTagHashCode(locktag);
partitionLock = LockHashPartitionLock(hashcode);
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
/*
* Re-find the lock object (it had better be there).
*/
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(void *) locktag,
hashcode,
HASH_FIND,
NULL);
if (!lock)
elog(PANIC, "failed to re-find shared lock object");
/*
* Re-find the proclock object (ditto).
*/
proclocktag.myLock = lock;
proclocktag.myProc = proc;
proclock_hashcode = ProcLockHashCode(&proclocktag, hashcode);
proclock = (PROCLOCK *) hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &proclocktag,
proclock_hashcode,
HASH_FIND,
NULL);
if (!proclock)
elog(PANIC, "failed to re-find shared proclock object");
/*
* Double-check that we are actually holding a lock of the type we want to
* release.
*/
if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
{
PROCLOCK_PRINT("lock_twophase_postcommit: WRONGTYPE", proclock);
LWLockRelease(partitionLock);
elog(WARNING, "you don't own a lock of type %s",
lockMethodTable->lockModeNames[lockmode]);
return;
}
/*
* Do the releasing. CleanUpLock will waken any now-wakable waiters.
*/
wakeupNeeded = UnGrantLock(lock, lockmode, proclock, lockMethodTable);
CleanUpLock(lock, proclock,
lockMethodTable, hashcode,
wakeupNeeded);
LWLockRelease(partitionLock);
/*
* Decrement strong lock count. This logic is needed only for 2PC.
*/
if (decrement_strong_lock_count
&& ConflictsWithRelationFastPath(locktag, lockmode))
{
uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
Assert(FastPathStrongRelationLocks->count[fasthashcode] > 0);
FastPathStrongRelationLocks->count[fasthashcode]--;
SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
}
/*
* Prepare for prepare, while we're still in a transaction.
*
* This marks LOCALLOCK objects on temporary tables, so that we can
* ignore them while writing the prepare record. Figuring out which
* tables are temporary requires catalog access, hence we must do this
* before we start actually preparing.
*
* If new locks are taken after this, they will be considered as
* not temp.
*/
void
PrePrepare_Locks(void)
{
HASH_SEQ_STATUS status;
LOCALLOCK *locallock;
/*
* Scan the local locks, and set the 'istemptable' flags.
*/
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
{
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
bool haveSessionLock;
bool haveXactLock;
int i;
locallock->istemptable = false;
/*
* Skip locks that would be ignored by AtPrepare_Locks() anyway.
*
* NOTE: these conditions should be kept in sync with AtPrepare_Locks()!
*/
/*
* Ignore VXID locks. We don't want those to be held by prepared
* transactions, since they aren't meaningful after a restart.
*/
if (locallock->tag.lock.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
continue;
/* Ignore it if we don't actually hold the lock */
if (locallock->nLocks <= 0)
continue;
/* Scan to see whether we hold it at session or transaction level */
haveSessionLock = haveXactLock = false;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (lockOwners[i].owner == NULL)
haveSessionLock = true;
else
haveXactLock = true;
}
/* Ignore it if we have only session lock */
if (!haveXactLock)
continue;
/*
* If we have both session- and transaction-level locks, fail. This
* should never happen with regular locks, since we only take those at
* session level in some special operations like VACUUM. It's
* possible to hit this with advisory locks, though.
*
* It would be nice if we could keep the session hold and give away
* the transactional hold to the prepared xact. However, that would
* require two PROCLOCK objects, and we cannot be sure that another
* PROCLOCK will be available when it comes time for PostPrepare_Locks
* to do the deed. So for now, we error out while we can still do so
* safely.
*/
if (haveSessionLock)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE while holding both session-level and transaction-level locks on the same object")));
/* gp-change
*
* We allow 2PC commit transactions to include temp objects.
* After PREPARE we WILL NOT transfer locks on the temp objects
* into our 2PC record. Instead, we will keep them with the proc which
* will be released at the end of the session.
*
* There doesn't seem to be any reason not to do this. Once the txn
* is prepared, it will be committed or aborted regardless of the state
* of the temp table. and quite possibly, the temp table will be
* destroyed at the end of the session, while the transaction will be
* committed from another session.
*/
locallock->istemptable = LockTagIsTemp(&locallock->tag.lock);
}
}
/*
* AtPrepare_Locks
* Do the preparatory work for a PREPARE: make 2PC state file records
* for all locks currently held.
*
* Session-level locks are ignored, as are VXID locks.
*
* There are some special cases that we error out on: we can't be holding any
* locks at both session and transaction level (since we must either keep or
* give away the PROCLOCK object), and we can't be holding any locks on
* temporary objects (since that would mess up the current backend if it tries
* to exit before the prepared xact is committed).
*/
void
AtPrepare_Locks(void)
{
HASH_SEQ_STATUS status;
LOCALLOCK *locallock;
/*
* For the most part, we don't need to touch shared memory for this ---
* all the necessary state information is in the locallock table.
* Fast-path locks are an exception, however: we move any such locks to
* the main table before allowing PREPARE TRANSACTION to succeed.
*/
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
{
TwoPhaseLockRecord record;
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
bool haveSessionLock;
bool haveXactLock;
int i;
/*
* Ignore VXID locks. We don't want those to be held by prepared
* transactions, since they aren't meaningful after a restart.
*/
if (locallock->tag.lock.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
continue;
/* Ignore it if we don't actually hold the lock */
if (locallock->nLocks <= 0)
continue;
/* Scan to see whether we hold it at session or transaction level */
haveSessionLock = haveXactLock = false;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (lockOwners[i].owner == NULL)
haveSessionLock = true;
else
haveXactLock = true;
}
/* Ignore it if we have only session lock */
if (!haveXactLock)
continue;
/*
* If we have both session- and transaction-level locks, fail. This
* should never happen with regular locks, since we only take those at
* session level in some special operations like VACUUM. It's
* possible to hit this with advisory locks, though.
*
* It would be nice if we could keep the session hold and give away
* the transactional hold to the prepared xact. However, that would
* require two PROCLOCK objects, and we cannot be sure that another
* PROCLOCK will be available when it comes time for PostPrepare_Locks
* to do the deed. So for now, we error out while we can still do so
* safely.
*/
if (haveSessionLock)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE while holding both session-level and transaction-level locks on the same object")));
/*
* If the local lock was taken via the fast-path, we need to move it
* to the primary lock table, or just get a pointer to the existing
* primary lock table entry if by chance it's already been
* transferred.
*/
if (locallock->proclock == NULL)
{
locallock->proclock = FastPathGetRelationLockEntry(locallock);
locallock->lock = locallock->proclock->tag.myLock;
}
/*
* Arrange to not release any strong lock count held by this lock
* entry. We must retain the count until the prepared transaction is
* committed or rolled back.
*/
locallock->holdsStrongLockCount = false;
/* gp-change
*
* We allow 2PC commit transactions to include temp objects.
* After PREPARE we WILL NOT transfer locks on the temp objects
* into our 2PC record. Instead, we will keep them with the proc which
* will be released at the end of the session.
*
* There doesn't seem to be any reason not to do this. Once the txn
* is prepared, it will be committed or aborted regardless of the state
* of the temp table. and quite possibly, the temp table will be
* destroyed at the end of the session, while the transaction will be
* committed from another session.
*/
if (locallock->istemptable)
continue;
/*
* Create a 2PC record.
*/
memcpy(&(record.locktag), &(locallock->tag.lock), sizeof(LOCKTAG));
record.lockmode = locallock->tag.mode;
RegisterTwoPhaseRecord(TWOPHASE_RM_LOCK_ID, 0,
&record, sizeof(TwoPhaseLockRecord));
}
}
/*
* PostPrepare_Locks
* Clean up after successful PREPARE
*
* Here, we want to transfer ownership of our locks to a dummy PGPROC
* that's now associated with the prepared transaction, and we want to
* clean out the corresponding entries in the LOCALLOCK table.
*
* Note: by removing the LOCALLOCK entries, we are leaving dangling
* pointers in the transaction's resource owner. This is OK at the
* moment since resowner.c doesn't try to free locks retail at a toplevel
* transaction commit or abort. We could alternatively zero out nLocks
* and leave the LOCALLOCK entries to be garbage-collected by LockReleaseAll,
* but that probably costs more cycles.
*/
void
PostPrepare_Locks(TransactionId xid)
{
PGPROC *newproc = TwoPhaseGetDummyProc(xid, false);
HASH_SEQ_STATUS status;
LOCALLOCK *locallock;
LOCK *lock;
PROCLOCK *proclock;
PROCLOCKTAG proclocktag;
int partition;
/* Can't prepare a lock group follower. */
Assert(MyProc->lockGroupLeader == NULL ||
MyProc->lockGroupLeader == MyProc);
/* This is a critical section: any error means big trouble */
START_CRIT_SECTION();
/*
* First we run through the locallock table and get rid of unwanted
* entries, then we scan the process's proclocks and transfer them to the
* target proc.
*
* We do this separately because we may have multiple locallock entries
* pointing to the same proclock, and we daren't end up with any dangling
* pointers.
*/
hash_seq_init(&status, LockMethodLocalHash);
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
{
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
bool haveSessionLock;
bool haveXactLock;
int i;
if (locallock->proclock == NULL || locallock->lock == NULL)
{
/*
* We must've run out of shared memory while trying to set up this
* lock. Just forget the local entry.
*/
Assert(locallock->nLocks == 0);
RemoveLocalLock(locallock);
continue;
}
/* Ignore VXID locks */
if (locallock->tag.lock.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
continue;
/* MPP change for temp objects in 2PC. we skip over temp objects. */
if (locallock->istemptable)
continue;
/* Scan to see whether we hold it at session or transaction level */
haveSessionLock = haveXactLock = false;
for (i = locallock->numLockOwners - 1; i >= 0; i--)
{
if (lockOwners[i].owner == NULL)
haveSessionLock = true;
else
haveXactLock = true;
}
/* Ignore it if we have only session lock */
if (!haveXactLock)
continue;
/* This can't happen, because we already checked it */
if (haveSessionLock)
ereport(PANIC,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot PREPARE while holding both session-level and transaction-level locks on the same object")));
/* Mark the proclock to show we need to release this lockmode */
if (locallock->nLocks > 0)
locallock->proclock->releaseMask |= LOCKBIT_ON(locallock->tag.mode);
/* And remove the locallock hashtable entry */
RemoveLocalLock(locallock);
}
/*
* Now, scan each lock partition separately.
*/
for (partition = 0; partition < NUM_LOCK_PARTITIONS; partition++)
{
LWLock *partitionLock;
SHM_QUEUE *procLocks = &(MyProc->myProcLocks[partition]);
PROCLOCK *nextplock;
partitionLock = LockHashPartitionLockByIndex(partition);
/*
* If the proclock list for this partition is empty, we can skip
* acquiring the partition lock. This optimization is safer than the
* situation in LockReleaseAll, because we got rid of any fast-path
* locks during AtPrepare_Locks, so there cannot be any case where
* another backend is adding something to our lists now. For safety,
* though, we code this the same way as in LockReleaseAll.
*/
if (SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, procLink)) == NULL)
continue; /* needn't examine this partition */
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
for (proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, procLink));
proclock;
proclock = nextplock)
{
/* Get link first, since we may unlink/relink this proclock */
nextplock = (PROCLOCK *)
SHMQueueNext(procLocks, &proclock->procLink,
offsetof(PROCLOCK, procLink));
Assert(proclock->tag.myProc == MyProc);
lock = proclock->tag.myLock;
/* MPP change for support of temp objects in 2PC.
*
* The case where the releaseMask is different than the holdMask is only
* for session locks. Temp objects is the only session lock we could
* have here and we DO NOT want to release this lock. so we
* skip over it.
*/
if (proclock->releaseMask != proclock->holdMask)
continue;
/* Ignore VXID locks */
if (lock->tag.locktag_type == LOCKTAG_VIRTUALTRANSACTION)
continue;
PROCLOCK_PRINT("PostPrepare_Locks", proclock);
LOCK_PRINT("PostPrepare_Locks", lock, 0);
Assert(lock->nRequested >= 0);
Assert(lock->nGranted >= 0);
Assert(lock->nGranted <= lock->nRequested);
Assert((proclock->holdMask & ~lock->grantMask) == 0);
/* Ignore it if nothing to release (must be a session lock) */
if (proclock->releaseMask == 0)
continue;
/* Else we should be releasing all locks */
if (proclock->releaseMask != proclock->holdMask)
elog(PANIC, "we seem to have dropped a bit somewhere");
/*
* We cannot simply modify proclock->tag.myProc to reassign
* ownership of the lock, because that's part of the hash key and
* the proclock would then be in the wrong hash chain. Instead
* use hash_update_hash_key. (We used to create a new hash entry,
* but that risks out-of-memory failure if other processes are
* busy making proclocks too.) We must unlink the proclock from
* our procLink chain and put it into the new proc's chain, too.
*
* Note: the updated proclock hash key will still belong to the
* same hash partition, cf proclock_hash(). So the partition lock
* we already hold is sufficient for this.
*/
SHMQueueDelete(&proclock->procLink);
/*
* Create the new hash key for the proclock.
*/
proclocktag.myLock = lock;
proclocktag.myProc = newproc;
/*
* Update groupLeader pointer to point to the new proc. (We'd
* better not be a member of somebody else's lock group!)
*/
Assert(proclock->groupLeader == proclock->tag.myProc);
proclock->groupLeader = newproc;
/*
* Update the proclock. We should not find any existing entry for
* the same hash key, since there can be only one entry for any
* given lock with my own proc.
*/
if (!hash_update_hash_key(LockMethodProcLockHash,
(void *) proclock,
(void *) &proclocktag))
elog(PANIC, "duplicate entry found while reassigning a prepared transaction's locks");
/* Re-link into the new proc's proclock list */
SHMQueueInsertBefore(&(newproc->myProcLocks[partition]),
&proclock->procLink);
PROCLOCK_PRINT("PostPrepare_Locks: updated", proclock);
} /* loop over PROCLOCKs within this partition */
LWLockRelease(partitionLock);
} /* loop over partitions */
END_CRIT_SECTION();
}
/*
* Estimate shared-memory space used for lock tables
*/
Size
LockShmemSize(void)
{
Size size = 0;
long max_table_size;
/* lock hash table */
max_table_size = NLOCKENTS();
if (Gp_role == GP_ROLE_DISPATCH && IsResQueueEnabled())
{
max_table_size = add_size(max_table_size, NRESLOCKENTS() );
}
size = add_size(size, hash_estimate_size(max_table_size, sizeof(LOCK)));
if (Gp_role == GP_ROLE_DISPATCH && IsResQueueEnabled())
{
max_table_size = add_size(max_table_size, NRESPROCLOCKENTS() );
}
/* proclock hash table */
max_table_size *= 2;
size = add_size(size, hash_estimate_size(max_table_size, sizeof(PROCLOCK)));
/*
* Since NLOCKENTS is only an estimate, add 10% safety margin.
*/
size = add_size(size, size / 10);
return size;
}
/*
* GetLockStatusData - Return a summary of the lock manager's internal
* status, for use in a user-level reporting function.
*
* The return data consists of an array of LockInstanceData objects,
* which are a lightly abstracted version of the PROCLOCK data structures,
* i.e. there is one entry for each unique lock and interested PGPROC.
* It is the caller's responsibility to match up related items (such as
* references to the same lockable object or PGPROC) if wanted.
*
* The design goal is to hold the LWLocks for as short a time as possible;
* thus, this function simply makes a copy of the necessary data and releases
* the locks, allowing the caller to contemplate and format the data for as
* long as it pleases.
*/
LockData *
GetLockStatusData(void)
{
LockData *data;
PROCLOCK *proclock;
HASH_SEQ_STATUS seqstat;
int els;
int el;
int i;
data = (LockData *) palloc(sizeof(LockData));
/* Guess how much space we'll need. */
els = MaxBackends;
el = 0;
data->locks = (LockInstanceData *) palloc(sizeof(LockInstanceData) * els);
/*
* First, we iterate through the per-backend fast-path arrays, locking
* them one at a time. This might produce an inconsistent picture of the
* system state, but taking all of those LWLocks at the same time seems
* impractical (in particular, note MAX_SIMUL_LWLOCKS). It shouldn't
* matter too much, because none of these locks can be involved in lock
* conflicts anyway - anything that might must be present in the main lock
* table. (For the same reason, we don't sweat about making leaderPid
* completely valid. We cannot safely dereference another backend's
* lockGroupLeader field without holding all lock partition locks, and
* it's not worth that.)
*/
for (i = 0; i < ProcGlobal->allProcCount; ++i)
{
PGPROC *proc = &ProcGlobal->allProcs[i];
TMGXACT *tmGxact = &ProcGlobal->allTmGxact[i];
uint32 f;
DistributedTransactionId distribXid;
LWLockAcquire(&proc->backendLock, LW_SHARED);
distribXid = (Gp_role == GP_ROLE_DISPATCH)? tmGxact->gxid : proc->localDistribXactData.distribXid;
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; ++f)
{
LockInstanceData *instance;
uint32 lockbits = FAST_PATH_GET_BITS(proc, f);
uint32 holdTillEndXactBits = FAST_PATH_GET_HOLD_TILL_END_XACT_BITS(proc, f);
/* Skip unallocated slots. */
if (!lockbits)
continue;
if (el >= els)
{
els += MaxBackends;
data->locks = (LockInstanceData *)
repalloc(data->locks, sizeof(LockInstanceData) * els);
}
instance = &data->locks[el];
SET_LOCKTAG_RELATION(instance->locktag, proc->databaseId,
proc->fpRelId[f]);
instance->holdMask = lockbits << FAST_PATH_LOCKNUMBER_OFFSET;
instance->waitLockMode = NoLock;
instance->backend = proc->backendId;
instance->lxid = proc->lxid;
instance->pid = proc->pid;
instance->leaderPid = proc->pid;
instance->fastpath = true;
instance->databaseId = proc->databaseId;
instance->mppSessionId = proc->mppSessionId;
instance->mppIsWriter = proc->mppIsWriter;
instance->distribXid = distribXid;
instance->holdTillEndXact = (holdTillEndXactBits > 0);
el++;
}
if (proc->fpVXIDLock)
{
VirtualTransactionId vxid;
LockInstanceData *instance;
if (el >= els)
{
els += MaxBackends;
data->locks = (LockInstanceData *)
repalloc(data->locks, sizeof(LockInstanceData) * els);
}
vxid.backendId = proc->backendId;
vxid.localTransactionId = proc->fpLocalTransactionId;
instance = &data->locks[el];
SET_LOCKTAG_VIRTUALTRANSACTION(instance->locktag, vxid);
instance->holdMask = LOCKBIT_ON(ExclusiveLock);
instance->waitLockMode = NoLock;
instance->backend = proc->backendId;
instance->lxid = proc->lxid;
instance->pid = proc->pid;
instance->leaderPid = proc->pid;
instance->fastpath = true;
instance->databaseId = proc->databaseId;
instance->mppSessionId = proc->mppSessionId;
instance->mppIsWriter = proc->mppIsWriter;
instance->distribXid = distribXid;
instance->holdTillEndXact = false;
el++;
}
LWLockRelease(&proc->backendLock);
}
/*
* Next, acquire lock on the entire shared lock data structure. We do
* this so that, at least for locks in the primary lock table, the state
* will be self-consistent.
*
* Since this is a read-only operation, we take shared instead of
* exclusive lock. There's not a whole lot of point to this, because all
* the normal operations require exclusive lock, but it doesn't hurt
* anything either. It will at least allow two backends to do
* GetLockStatusData in parallel.
*
* Must grab LWLocks in partition-number order to avoid LWLock deadlock.
*/
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
LWLockAcquire(LockHashPartitionLockByIndex(i), LW_SHARED);
/* Now we can safely count the number of proclocks */
data->nelements = el + hash_get_num_entries(LockMethodProcLockHash);
if (data->nelements > els)
{
els = data->nelements;
data->locks = (LockInstanceData *)
repalloc(data->locks, sizeof(LockInstanceData) * els);
}
/* Now scan the tables to copy the data */
hash_seq_init(&seqstat, LockMethodProcLockHash);
while ((proclock = (PROCLOCK *) hash_seq_search(&seqstat)))
{
PGPROC *proc = proclock->tag.myProc;
LOCK *lock = proclock->tag.myLock;
LockInstanceData *instance = &data->locks[el];
TMGXACT *tmGxact = &ProcGlobal->allTmGxact[proc->pgprocno];
memcpy(&instance->locktag, &lock->tag, sizeof(LOCKTAG));
instance->holdMask = proclock->holdMask;
if (proc->waitLock == proclock->tag.myLock)
instance->waitLockMode = proc->waitLockMode;
else
instance->waitLockMode = NoLock;
instance->backend = proc->backendId;
instance->lxid = proc->lxid;
instance->pid = proc->pid;
instance->leaderPid = proclock->groupLeader->pid;
instance->fastpath = false;
instance->databaseId = proc->databaseId;
instance->mppSessionId = proc->mppSessionId;
instance->mppIsWriter = proc->mppIsWriter;
instance->distribXid = (Gp_role == GP_ROLE_DISPATCH)?
tmGxact->gxid :
proc->localDistribXactData.distribXid;
instance->holdTillEndXact = proclock->tag.myLock->holdTillEndXact;
el++;
}
/*
* And release locks. We do this in reverse order for two reasons: (1)
* Anyone else who needs more than one of the locks will be trying to lock
* them in increasing order; we don't want to release the other process
* until it can get all the locks it needs. (2) This avoids O(N^2)
* behavior inside LWLockRelease.
*/
for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
LWLockRelease(LockHashPartitionLockByIndex(i));
Assert(el == data->nelements);
return data;
}
/*
* GetBlockerStatusData - Return a summary of the lock manager's state
* concerning locks that are blocking the specified PID or any member of
* the PID's lock group, for use in a user-level reporting function.
*
* For each PID within the lock group that is awaiting some heavyweight lock,
* the return data includes an array of LockInstanceData objects, which are
* the same data structure used by GetLockStatusData; but unlike that function,
* this one reports only the PROCLOCKs associated with the lock that that PID
* is blocked on. (Hence, all the locktags should be the same for any one
* blocked PID.) In addition, we return an array of the PIDs of those backends
* that are ahead of the blocked PID in the lock's wait queue. These can be
* compared with the PIDs in the LockInstanceData objects to determine which
* waiters are ahead of or behind the blocked PID in the queue.
*
* If blocked_pid isn't a valid backend PID or nothing in its lock group is
* waiting on any heavyweight lock, return empty arrays.
*
* The design goal is to hold the LWLocks for as short a time as possible;
* thus, this function simply makes a copy of the necessary data and releases
* the locks, allowing the caller to contemplate and format the data for as
* long as it pleases.
*/
BlockedProcsData *
GetBlockerStatusData(int blocked_pid)
{
BlockedProcsData *data;
PGPROC *proc;
int i;
data = (BlockedProcsData *) palloc(sizeof(BlockedProcsData));
/*
* Guess how much space we'll need, and preallocate. Most of the time
* this will avoid needing to do repalloc while holding the LWLocks. (We
* assume, but check with an Assert, that MaxBackends is enough entries
* for the procs[] array; the other two could need enlargement, though.)
*/
data->nprocs = data->nlocks = data->npids = 0;
data->maxprocs = data->maxlocks = data->maxpids = MaxBackends;
data->procs = (BlockedProcData *) palloc(sizeof(BlockedProcData) * data->maxprocs);
data->locks = (LockInstanceData *) palloc(sizeof(LockInstanceData) * data->maxlocks);
data->waiter_pids = (int *) palloc(sizeof(int) * data->maxpids);
/*
* In order to search the ProcArray for blocked_pid and assume that that
* entry won't immediately disappear under us, we must hold ProcArrayLock.
* In addition, to examine the lock grouping fields of any other backend,
* we must hold all the hash partition locks. (Only one of those locks is
* actually relevant for any one lock group, but we can't know which one
* ahead of time.) It's fairly annoying to hold all those locks
* throughout this, but it's no worse than GetLockStatusData(), and it
* does have the advantage that we're guaranteed to return a
* self-consistent instantaneous state.
*/
LWLockAcquire(ProcArrayLock, LW_SHARED);
proc = BackendPidGetProcWithLock(blocked_pid);
/* Nothing to do if it's gone */
if (proc != NULL)
{
/*
* Acquire lock on the entire shared lock data structure. See notes
* in GetLockStatusData().
*/
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
LWLockAcquire(LockHashPartitionLockByIndex(i), LW_SHARED);
if (proc->lockGroupLeader == NULL)
{
/* Easy case, proc is not a lock group member */
GetSingleProcBlockerStatusData(proc, data);
}
else
{
/* Examine all procs in proc's lock group */
dlist_iter iter;
dlist_foreach(iter, &proc->lockGroupLeader->lockGroupMembers)
{
PGPROC *memberProc;
memberProc = dlist_container(PGPROC, lockGroupLink, iter.cur);
GetSingleProcBlockerStatusData(memberProc, data);
}
}
/*
* And release locks. See notes in GetLockStatusData().
*/
for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
LWLockRelease(LockHashPartitionLockByIndex(i));
Assert(data->nprocs <= data->maxprocs);
}
LWLockRelease(ProcArrayLock);
return data;
}
/* Accumulate data about one possibly-blocked proc for GetBlockerStatusData */
static void
GetSingleProcBlockerStatusData(PGPROC *blocked_proc, BlockedProcsData *data)
{
LOCK *theLock = blocked_proc->waitLock;
BlockedProcData *bproc;
SHM_QUEUE *procLocks;
PROCLOCK *proclock;
PROC_QUEUE *waitQueue;
PGPROC *proc;
int queue_size;
int i;
/* Nothing to do if this proc is not blocked */
if (theLock == NULL)
return;
/* Set up a procs[] element */
bproc = &data->procs[data->nprocs++];
bproc->pid = blocked_proc->pid;
bproc->first_lock = data->nlocks;
bproc->first_waiter = data->npids;
/*
* We may ignore the proc's fast-path arrays, since nothing in those could
* be related to a contended lock.
*/
/* Collect all PROCLOCKs associated with theLock */
procLocks = &(theLock->procLocks);
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, lockLink));
while (proclock)
{
PGPROC *proc = proclock->tag.myProc;
LOCK *lock = proclock->tag.myLock;
LockInstanceData *instance;
if (data->nlocks >= data->maxlocks)
{
data->maxlocks += MaxBackends;
data->locks = (LockInstanceData *)
repalloc(data->locks, sizeof(LockInstanceData) * data->maxlocks);
}
instance = &data->locks[data->nlocks];
memcpy(&instance->locktag, &lock->tag, sizeof(LOCKTAG));
instance->holdMask = proclock->holdMask;
if (proc->waitLock == lock)
instance->waitLockMode = proc->waitLockMode;
else
instance->waitLockMode = NoLock;
instance->backend = proc->backendId;
instance->lxid = proc->lxid;
instance->pid = proc->pid;
instance->leaderPid = proclock->groupLeader->pid;
instance->fastpath = false;
data->nlocks++;
proclock = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->lockLink,
offsetof(PROCLOCK, lockLink));
}
/* Enlarge waiter_pids[] if it's too small to hold all wait queue PIDs */
waitQueue = &(theLock->waitProcs);
queue_size = waitQueue->size;
if (queue_size > data->maxpids - data->npids)
{
data->maxpids = Max(data->maxpids + MaxBackends,
data->npids + queue_size);
data->waiter_pids = (int *) repalloc(data->waiter_pids,
sizeof(int) * data->maxpids);
}
/* Collect PIDs from the lock's wait queue, stopping at blocked_proc */
proc = (PGPROC *) waitQueue->links.next;
for (i = 0; i < queue_size; i++)
{
if (proc == blocked_proc)
break;
data->waiter_pids[data->npids++] = proc->pid;
proc = (PGPROC *) proc->links.next;
}
bproc->num_locks = data->nlocks - bproc->first_lock;
bproc->num_waiters = data->npids - bproc->first_waiter;
}
/*
* Returns a list of currently held AccessExclusiveLocks, for use by
* LogStandbySnapshot(). The result is a palloc'd array,
* with the number of elements returned into *nlocks.
*
* XXX This currently takes a lock on all partitions of the lock table,
* but it's possible to do better. By reference counting locks and storing
* the value in the ProcArray entry for each backend we could tell if any
* locks need recording without having to acquire the partition locks and
* scan the lock table. Whether that's worth the additional overhead
* is pretty dubious though.
*/
xl_standby_lock *
GetRunningTransactionLocks(int *nlocks)
{
xl_standby_lock *accessExclusiveLocks;
PROCLOCK *proclock;
HASH_SEQ_STATUS seqstat;
int i;
int index;
int els;
/*
* Acquire lock on the entire shared lock data structure.
*
* Must grab LWLocks in partition-number order to avoid LWLock deadlock.
*/
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
LWLockAcquire(LockHashPartitionLockByIndex(i), LW_SHARED);
/* Now we can safely count the number of proclocks */
els = hash_get_num_entries(LockMethodProcLockHash);
/*
* Allocating enough space for all locks in the lock table is overkill,
* but it's more convenient and faster than having to enlarge the array.
*/
accessExclusiveLocks = palloc(els * sizeof(xl_standby_lock));
/* Now scan the tables to copy the data */
hash_seq_init(&seqstat, LockMethodProcLockHash);
/*
* If lock is a currently granted AccessExclusiveLock then it will have
* just one proclock holder, so locks are never accessed twice in this
* particular case. Don't copy this code for use elsewhere because in the
* general case this will give you duplicate locks when looking at
* non-exclusive lock types.
*/
index = 0;
while ((proclock = (PROCLOCK *) hash_seq_search(&seqstat)))
{
/* make sure this definition matches the one used in LockAcquire */
if ((proclock->holdMask & LOCKBIT_ON(AccessExclusiveLock)) &&
proclock->tag.myLock->tag.locktag_type == LOCKTAG_RELATION)
{
PGPROC *proc = proclock->tag.myProc;
PGXACT *pgxact = &ProcGlobal->allPgXact[proc->pgprocno];
LOCK *lock = proclock->tag.myLock;
TransactionId xid = pgxact->xid;
/*
* Don't record locks for transactions if we know they have
* already issued their WAL record for commit but not yet released
* lock. It is still possible that we see locks held by already
* complete transactions, if they haven't yet zeroed their xids.
*/
if (!TransactionIdIsValid(xid))
continue;
accessExclusiveLocks[index].xid = xid;
accessExclusiveLocks[index].dbOid = lock->tag.locktag_field1;
accessExclusiveLocks[index].relOid = lock->tag.locktag_field2;
index++;
}
}
Assert(index <= els);
/*
* And release locks. We do this in reverse order for two reasons: (1)
* Anyone else who needs more than one of the locks will be trying to lock
* them in increasing order; we don't want to release the other process
* until it can get all the locks it needs. (2) This avoids O(N^2)
* behavior inside LWLockRelease.
*/
for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
LWLockRelease(LockHashPartitionLockByIndex(i));
*nlocks = index;
return accessExclusiveLocks;
}
/* Provide the textual name of any lock mode */
const char *
GetLockmodeName(LOCKMETHODID lockmethodid, LOCKMODE mode)
{
Assert(lockmethodid > 0 && lockmethodid < lengthof(LockMethods));
Assert(mode > 0 && mode <= LockMethods[lockmethodid]->numLockModes);
return LockMethods[lockmethodid]->lockModeNames[mode];
}
#ifdef LOCK_DEBUG
/*
* Dump all locks in the given proc's myProcLocks lists.
*
* Caller is responsible for having acquired appropriate LWLocks.
*/
void
DumpLocks(PGPROC *proc)
{
SHM_QUEUE *procLocks;
PROCLOCK *proclock;
LOCK *lock;
int i;
if (proc == NULL)
return;
if (proc->waitLock)
LOCK_PRINT("DumpLocks: waiting on", proc->waitLock, 0);
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
{
procLocks = &(proc->myProcLocks[i]);
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
offsetof(PROCLOCK, procLink));
while (proclock)
{
Assert(proclock->tag.myProc == proc);
lock = proclock->tag.myLock;
PROCLOCK_PRINT("DumpLocks", proclock);
LOCK_PRINT("DumpLocks", lock, 0);
proclock = (PROCLOCK *)
SHMQueueNext(procLocks, &proclock->procLink,
offsetof(PROCLOCK, procLink));
}
}
}
/*
* Dump all lmgr locks.
*
* Caller is responsible for having acquired appropriate LWLocks.
*/
void
DumpAllLocks(void)
{
PGPROC *proc;
PROCLOCK *proclock;
LOCK *lock;
HASH_SEQ_STATUS status;
proc = MyProc;
if (proc && proc->waitLock)
LOCK_PRINT("DumpAllLocks: waiting on", proc->waitLock, 0);
hash_seq_init(&status, LockMethodProcLockHash);
while ((proclock = (PROCLOCK *) hash_seq_search(&status)) != NULL)
{
PROCLOCK_PRINT("DumpAllLocks", proclock);
lock = proclock->tag.myLock;
if (lock)
LOCK_PRINT("DumpAllLocks", lock, 0);
else
elog(LOG, "DumpAllLocks: proclock->tag.myLock = NULL");
}
}
#endif /* LOCK_DEBUG */
/*
* LOCK 2PC resource manager's routines
*/
/*
* Re-acquire a lock belonging to a transaction that was prepared.
*
* Because this function is run at db startup, re-acquiring the locks should
* never conflict with running transactions because there are none. We
* assume that the lock state represented by the stored 2PC files is legal.
*
* When switching from Hot Standby mode to normal operation, the locks will
* be already held by the startup process. The locks are acquired for the new
* procs without checking for conflicts, so we don't get a conflict between the
* startup process and the dummy procs, even though we will momentarily have
* a situation where two procs are holding the same AccessExclusiveLock,
* which isn't normally possible because the conflict. If we're in standby
* mode, but a recovery snapshot hasn't been established yet, it's possible
* that some but not all of the locks are already held by the startup process.
*
* This approach is simple, but also a bit dangerous, because if there isn't
* enough shared memory to acquire the locks, an error will be thrown, which
* is promoted to FATAL and recovery will abort, bringing down postmaster.
* A safer approach would be to transfer the locks like we do in
* AtPrepare_Locks, but then again, in hot standby mode it's possible for
* read-only backends to use up all the shared lock memory anyway, so that
* replaying the WAL record that needs to acquire a lock will throw an error
* and PANIC anyway.
*/
void
lock_twophase_recover(TransactionId xid, uint16 info,
void *recdata, uint32 len)
{
TwoPhaseLockRecord *rec = (TwoPhaseLockRecord *) recdata;
PGPROC *proc = TwoPhaseGetDummyProc(xid, false);
LOCKTAG *locktag;
LOCKMODE lockmode;
LOCKMETHODID lockmethodid;
LOCK *lock;
PROCLOCK *proclock;
PROCLOCKTAG proclocktag;
bool found;
uint32 hashcode;
uint32 proclock_hashcode;
int partition;
LWLock *partitionLock;
LockMethod lockMethodTable;
Assert(len == sizeof(TwoPhaseLockRecord));
locktag = &rec->locktag;
lockmode = rec->lockmode;
lockmethodid = locktag->locktag_lockmethodid;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
hashcode = LockTagHashCode(locktag);
partition = LockHashPartition(hashcode);
partitionLock = LockHashPartitionLock(hashcode);
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
/*
* Find or create a lock with this tag.
*/
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(void *) locktag,
hashcode,
HASH_ENTER_NULL,
&found);
if (!lock)
{
LWLockRelease(partitionLock);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory"),
errhint("You might need to increase max_locks_per_transaction.")));
}
/*
* if it's a new lock object, initialize it
*/
if (!found)
{
lock->grantMask = 0;
lock->waitMask = 0;
SHMQueueInit(&(lock->procLocks));
ProcQueueInit(&(lock->waitProcs));
lock->nRequested = 0;
lock->nGranted = 0;
lock->holdTillEndXact = false;
MemSet(lock->requested, 0, sizeof(int) * MAX_LOCKMODES);
MemSet(lock->granted, 0, sizeof(int) * MAX_LOCKMODES);
LOCK_PRINT("lock_twophase_recover: new", lock, lockmode);
}
else
{
LOCK_PRINT("lock_twophase_recover: found", lock, lockmode);
Assert((lock->nRequested >= 0) && (lock->requested[lockmode] >= 0));
Assert((lock->nGranted >= 0) && (lock->granted[lockmode] >= 0));
Assert(lock->nGranted <= lock->nRequested);
}
/*
* Create the hash key for the proclock table.
*/
proclocktag.myLock = lock;
proclocktag.myProc = proc;
proclock_hashcode = ProcLockHashCode(&proclocktag, hashcode);
/*
* Find or create a proclock entry with this tag
*/
proclock = (PROCLOCK *) hash_search_with_hash_value(LockMethodProcLockHash,
(void *) &proclocktag,
proclock_hashcode,
HASH_ENTER_NULL,
&found);
if (!proclock)
{
/* Oops, not enough shmem for the proclock */
if (lock->nRequested == 0)
{
/*
* There are no other requestors of this lock, so garbage-collect
* the lock object. We *must* do this to avoid a permanent leak
* of shared memory, because there won't be anything to cause
* anyone to release the lock object later.
*/
Assert(SHMQueueEmpty(&(lock->procLocks)));
if (!hash_search_with_hash_value(LockMethodLockHash,
(void *) &(lock->tag),
hashcode,
HASH_REMOVE,
NULL))
elog(PANIC, "lock table corrupted");
}
LWLockRelease(partitionLock);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory"),
errhint("You might need to increase max_locks_per_transaction.")));
}
/*
* If new, initialize the new entry
*/
if (!found)
{
Assert(proc->lockGroupLeader == NULL);
proclock->groupLeader = proc;
proclock->holdMask = 0;
proclock->releaseMask = 0;
/* Add proclock to appropriate lists */
SHMQueueInsertBefore(&lock->procLocks, &proclock->lockLink);
SHMQueueInsertBefore(&(proc->myProcLocks[partition]),
&proclock->procLink);
PROCLOCK_PRINT("lock_twophase_recover: new", proclock);
}
else
{
PROCLOCK_PRINT("lock_twophase_recover: found", proclock);
Assert((proclock->holdMask & ~lock->grantMask) == 0);
}
/*
* lock->nRequested and lock->requested[] count the total number of
* requests, whether granted or waiting, so increment those immediately.
*/
lock->nRequested++;
lock->requested[lockmode]++;
Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
/*
* We shouldn't already hold the desired lock.
*/
if (proclock->holdMask & LOCKBIT_ON(lockmode))
ereport(ERROR, (errmsg("lock %s on object %u/%u/%u is already held",
lockMethodTable->lockModeNames[lockmode],
lock->tag.locktag_field1, lock->tag.locktag_field2,
lock->tag.locktag_field3)));
/*
* We ignore any possible conflicts and just grant ourselves the lock. Not
* only because we don't bother, but also to avoid deadlocks when
* switching from standby to normal mode. See function comment.
*/
GrantLock(lock, proclock, lockmode);
/*
* Bump strong lock count, to make sure any fast-path lock requests won't
* be granted without consulting the primary lock table.
*/
if (ConflictsWithRelationFastPath(&lock->tag, lockmode))
{
uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode);
SpinLockAcquire(&FastPathStrongRelationLocks->mutex);
FastPathStrongRelationLocks->count[fasthashcode]++;
SpinLockRelease(&FastPathStrongRelationLocks->mutex);
}
LWLockRelease(partitionLock);
}
/*
* Re-acquire a lock belonging to a transaction that was prepared, when
* starting up into hot standby mode.
*/
void
lock_twophase_standby_recover(TransactionId xid, uint16 info,
void *recdata, uint32 len)
{
TwoPhaseLockRecord *rec = (TwoPhaseLockRecord *) recdata;
LOCKTAG *locktag;
LOCKMODE lockmode;
LOCKMETHODID lockmethodid;
Assert(len == sizeof(TwoPhaseLockRecord));
locktag = &rec->locktag;
lockmode = rec->lockmode;
lockmethodid = locktag->locktag_lockmethodid;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
if (lockmode == AccessExclusiveLock &&
locktag->locktag_type == LOCKTAG_RELATION)
{
StandbyAcquireAccessExclusiveLock(xid,
locktag->locktag_field1 /* dboid */ ,
locktag->locktag_field2 /* reloid */ );
}
}
/*
* 2PC processing routine for COMMIT PREPARED case.
*
* Find and release the lock indicated by the 2PC record.
*/
void
lock_twophase_postcommit(TransactionId xid, uint16 info,
void *recdata, uint32 len)
{
TwoPhaseLockRecord *rec = (TwoPhaseLockRecord *) recdata;
PGPROC *proc = TwoPhaseGetDummyProc(xid, true);
LOCKTAG *locktag;
LOCKMETHODID lockmethodid;
LockMethod lockMethodTable;
Assert(len == sizeof(TwoPhaseLockRecord));
locktag = &rec->locktag;
lockmethodid = locktag->locktag_lockmethodid;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
lockMethodTable = LockMethods[lockmethodid];
LockRefindAndRelease(lockMethodTable, proc, locktag, rec->lockmode, true);
}
/*
* 2PC processing routine for ROLLBACK PREPARED case.
*
* This is actually just the same as the COMMIT case.
*/
void
lock_twophase_postabort(TransactionId xid, uint16 info,
void *recdata, uint32 len)
{
lock_twophase_postcommit(xid, info, recdata, len);
}
/*
* VirtualXactLockTableInsert
*
* Take vxid lock via the fast-path. There can't be any pre-existing
* lockers, as we haven't advertised this vxid via the ProcArray yet.
*
* Since MyProc->fpLocalTransactionId will normally contain the same data
* as MyProc->lxid, you might wonder if we really need both. The
* difference is that MyProc->lxid is set and cleared unlocked, and
* examined by procarray.c, while fpLocalTransactionId is protected by
* backendLock and is used only by the locking subsystem. Doing it this
* way makes it easier to verify that there are no funny race conditions.
*
* We don't bother recording this lock in the local lock table, since it's
* only ever released at the end of a transaction. Instead,
* LockReleaseAll() calls VirtualXactLockTableCleanup().
*/
void
VirtualXactLockTableInsert(VirtualTransactionId vxid)
{
Assert(VirtualTransactionIdIsValid(vxid));
LWLockAcquire(&MyProc->backendLock, LW_EXCLUSIVE);
Assert(MyProc->backendId == vxid.backendId);
Assert(MyProc->fpLocalTransactionId == InvalidLocalTransactionId);
Assert(MyProc->fpVXIDLock == false);
MyProc->fpVXIDLock = true;
MyProc->fpLocalTransactionId = vxid.localTransactionId;
LWLockRelease(&MyProc->backendLock);
}
/*
* VirtualXactLockTableCleanup
*
* Check whether a VXID lock has been materialized; if so, release it,
* unblocking waiters.
*/
void
VirtualXactLockTableCleanup(void)
{
bool fastpath;
LocalTransactionId lxid;
Assert(MyProc->backendId != InvalidBackendId);
/*
* Clean up shared memory state.
*/
LWLockAcquire(&MyProc->backendLock, LW_EXCLUSIVE);
fastpath = MyProc->fpVXIDLock;
lxid = MyProc->fpLocalTransactionId;
MyProc->fpVXIDLock = false;
MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
LWLockRelease(&MyProc->backendLock);
/*
* If fpVXIDLock has been cleared without touching fpLocalTransactionId,
* that means someone transferred the lock to the main lock table.
*/
if (!fastpath && LocalTransactionIdIsValid(lxid))
{
VirtualTransactionId vxid;
LOCKTAG locktag;
vxid.backendId = MyBackendId;
vxid.localTransactionId = lxid;
SET_LOCKTAG_VIRTUALTRANSACTION(locktag, vxid);
LockRefindAndRelease(LockMethods[DEFAULT_LOCKMETHOD], MyProc,
&locktag, ExclusiveLock, false);
}
}
/*
* VirtualXactLock
*
* If wait = true, wait until the given VXID has been released, and then
* return true.
*
* If wait = false, just check whether the VXID is still running, and return
* true or false.
*/
bool
VirtualXactLock(VirtualTransactionId vxid, bool wait)
{
LOCKTAG tag;
PGPROC *proc;
Assert(VirtualTransactionIdIsValid(vxid));
SET_LOCKTAG_VIRTUALTRANSACTION(tag, vxid);
/*
* If a lock table entry must be made, this is the PGPROC on whose behalf
* it must be done. Note that the transaction might end or the PGPROC
* might be reassigned to a new backend before we get around to examining
* it, but it doesn't matter. If we find upon examination that the
* relevant lxid is no longer running here, that's enough to prove that
* it's no longer running anywhere.
*/
proc = BackendIdGetProc(vxid.backendId);
if (proc == NULL)
return true;
/*
* We must acquire this lock before checking the backendId and lxid
* against the ones we're waiting for. The target backend will only set
* or clear lxid while holding this lock.
*/
LWLockAcquire(&proc->backendLock, LW_EXCLUSIVE);
/* If the transaction has ended, our work here is done. */
if (proc->backendId != vxid.backendId
|| proc->fpLocalTransactionId != vxid.localTransactionId)
{
LWLockRelease(&proc->backendLock);
return true;
}
/*
* If we aren't asked to wait, there's no need to set up a lock table
* entry. The transaction is still in progress, so just return false.
*/
if (!wait)
{
LWLockRelease(&proc->backendLock);
return false;
}
/*
* OK, we're going to need to sleep on the VXID. But first, we must set
* up the primary lock table entry, if needed (ie, convert the proc's
* fast-path lock on its VXID to a regular lock).
*/
if (proc->fpVXIDLock)
{
PROCLOCK *proclock;
uint32 hashcode;
LWLock *partitionLock;
hashcode = LockTagHashCode(&tag);
partitionLock = LockHashPartitionLock(hashcode);
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
proclock = SetupLockInTable(LockMethods[DEFAULT_LOCKMETHOD], proc,
&tag, hashcode, ExclusiveLock);
if (!proclock)
{
LWLockRelease(partitionLock);
LWLockRelease(&proc->backendLock);
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of shared memory"),
errhint("You might need to increase max_locks_per_transaction.")));
}
GrantLock(proclock->tag.myLock, proclock, ExclusiveLock);
LWLockRelease(partitionLock);
proc->fpVXIDLock = false;
}
/* Done with proc->fpLockBits */
LWLockRelease(&proc->backendLock);
/* Time to wait. */
(void) LockAcquire(&tag, ShareLock, false, false);
LockRelease(&tag, ShareLock, false);
return true;
}
/*
* setFPHoldTillEndXact
* Some locks are acquired via fast path, this function is
* to set the HoldTillEndXact field for those relation locks.
*/
static bool
setFPHoldTillEndXact(Oid relid)
{
uint32 f;
bool result = false;
PGPROC *proc = MyProc;
LWLockAcquire(&proc->backendLock, LW_EXCLUSIVE);
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; ++f)
{
uint32 lockbits;
if (proc->fpRelId[f] != relid ||
(lockbits = FAST_PATH_GET_BITS(proc, f)) == 0)
continue;
/* one relid only occupies one slot. */
FAST_PATH_SET_HOLD_TILL_END_XACT(proc, f, lockbits);
result = true;
break;
}
LWLockRelease(&proc->backendLock);
return result;
}
/*
* Check whether a waiter's request lockmode conflict with
* the holder's hold mask
*/
bool
CheckWaitLockModeConflictHoldMask(LOCKTAG tag, LOCKMODE waitLockMode, LOCKMASK holderMask)
{
int waiterConflictMask;
LOCKMETHODID lockmethodid = (LOCKMETHODID) tag.locktag_lockmethodid;
Assert(0 < lockmethodid && lockmethodid < lengthof(LockMethods));
waiterConflictMask = LockMethods[lockmethodid]->conflictTab[waitLockMode];
if (holderMask & waiterConflictMask)
return true;
return false;
}
/*
* LockWaiterCount
*
* Find the number of lock requester on this locktag
*/
int
LockWaiterCount(const LOCKTAG *locktag)
{
LOCKMETHODID lockmethodid = locktag->locktag_lockmethodid;
LOCK *lock;
bool found;
uint32 hashcode;
LWLock *partitionLock;
int waiters = 0;
if (lockmethodid <= 0 || lockmethodid >= lengthof(LockMethods))
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
hashcode = LockTagHashCode(locktag);
partitionLock = LockHashPartitionLock(hashcode);
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
lock = (LOCK *) hash_search_with_hash_value(LockMethodLockHash,
(const void *) locktag,
hashcode,
HASH_FIND,
&found);
if (found)
{
Assert(lock != NULL);
waiters = lock->nRequested;
}
LWLockRelease(partitionLock);
return waiters;
}
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