diff options
Diffstat (limited to 'src/backend/commands')
| -rw-r--r-- | src/backend/commands/async.c | 37 | ||||
| -rw-r--r-- | src/backend/commands/vacuum.c | 13 |
2 files changed, 40 insertions, 10 deletions
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c index fb944911ee9..8e1c821cc5d 100644 --- a/src/backend/commands/async.c +++ b/src/backend/commands/async.c @@ -223,19 +223,22 @@ typedef struct QueueBackendStatus /* * Shared memory state for LISTEN/NOTIFY (excluding its SLRU stuff) * - * The AsyncQueueControl structure is protected by the AsyncQueueLock. + * The AsyncQueueControl structure is protected by the AsyncQueueLock and + * NotifyQueueTailLock. * - * When holding the lock in SHARED mode, backends may only inspect their own - * entries as well as the head and tail pointers. Consequently we can allow a - * backend to update its own record while holding only SHARED lock (since no - * other backend will inspect it). + * When holding AsyncQueueLock in SHARED mode, backends may only inspect their + * own entries as well as the head and tail pointers. Consequently we can + * allow a backend to update its own record while holding only SHARED lock + * (since no other backend will inspect it). * - * When holding the lock in EXCLUSIVE mode, backends can inspect the entries - * of other backends and also change the head and tail pointers. + * When holding AsyncQueueLock in EXCLUSIVE mode, backends can inspect the + * entries of other backends and also change the head pointer. When holding + * both AsyncQueueLock and NotifyQueueTailLock in EXCLUSIVE mode, backends can + * change the tail pointer. * * AsyncCtlLock is used as the control lock for the pg_notify SLRU buffers. - * In order to avoid deadlocks, whenever we need both locks, we always first - * get AsyncQueueLock and then AsyncCtlLock. + * In order to avoid deadlocks, whenever we need multiple locks, we first get + * NotifyQueueTailLock, then AsyncQueueLock, and lastly AsyncCtlLock. * * Each backend uses the backend[] array entry with index equal to its * BackendId (which can range from 1 to MaxBackends). We rely on this to make @@ -2012,6 +2015,10 @@ asyncQueueAdvanceTail(void) int newtailpage; int boundary; + /* Restrict task to one backend per cluster; see SimpleLruTruncate(). */ + LWLockAcquire(NotifyQueueTailLock, LW_EXCLUSIVE); + + /* Compute the new tail. */ LWLockAcquire(AsyncQueueLock, LW_EXCLUSIVE); min = QUEUE_HEAD; for (i = 1; i <= MaxBackends; i++) @@ -2020,7 +2027,6 @@ asyncQueueAdvanceTail(void) min = QUEUE_POS_MIN(min, QUEUE_BACKEND_POS(i)); } oldtailpage = QUEUE_POS_PAGE(QUEUE_TAIL); - QUEUE_TAIL = min; LWLockRelease(AsyncQueueLock); /* @@ -2040,6 +2046,17 @@ asyncQueueAdvanceTail(void) */ SimpleLruTruncate(AsyncCtl, newtailpage); } + + /* + * Advertise the new tail. This changes asyncQueueIsFull()'s verdict for + * the segment immediately prior to the new tail, allowing fresh data into + * that segment. + */ + LWLockAcquire(AsyncQueueLock, LW_EXCLUSIVE); + QUEUE_TAIL = min; + LWLockRelease(AsyncQueueLock); + + LWLockRelease(NotifyQueueTailLock); } /* diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 7c2ef933352..f5a0b600f9e 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -1296,6 +1296,14 @@ vac_update_datfrozenxid(void) bool dirty = false; /* + * Restrict this task to one backend per database. This avoids race + * conditions that would move datfrozenxid or datminmxid backward. It + * avoids calling vac_truncate_clog() with a datfrozenxid preceding a + * datfrozenxid passed to an earlier vac_truncate_clog() call. + */ + LockDatabaseFrozenIds(ExclusiveLock); + + /* * Initialize the "min" calculation with GetOldestXmin, which is a * reasonable approximation to the minimum relfrozenxid for not-yet- * committed pg_class entries for new tables; see AddNewRelationTuple(). @@ -1484,6 +1492,9 @@ vac_truncate_clog(TransactionId frozenXID, bool bogus = false; bool frozenAlreadyWrapped = false; + /* Restrict task to one backend per cluster; see SimpleLruTruncate(). */ + LWLockAcquire(WrapLimitsVacuumLock, LW_EXCLUSIVE); + /* init oldest datoids to sync with my frozenXID/minMulti values */ oldestxid_datoid = MyDatabaseId; minmulti_datoid = MyDatabaseId; @@ -1593,6 +1604,8 @@ vac_truncate_clog(TransactionId frozenXID, */ SetTransactionIdLimit(frozenXID, oldestxid_datoid); SetMultiXactIdLimit(minMulti, minmulti_datoid, false); + + LWLockRelease(WrapLimitsVacuumLock); } |