diff options
Diffstat (limited to 'src')
-rw-r--r-- | src/backend/access/transam/xact.c | 36 | ||||
-rw-r--r-- | src/backend/access/transam/xlog.c | 18 | ||||
-rw-r--r-- | src/include/storage/lwlock.h | 3 |
3 files changed, 47 insertions, 10 deletions
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 0023d47f13a..6c14ef36468 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.135.2.1 2002/11/18 01:17:50 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.135.2.2 2004/08/11 04:08:39 tgl Exp $ * * NOTES * Transaction aborts can now occur two ways: @@ -523,6 +523,7 @@ RecordTransactionCommit(void) if (MyXactMadeXLogEntry || MyXactMadeTempRelUpdate) { TransactionId xid = GetCurrentTransactionId(); + bool madeTCentries; XLogRecPtr recptr; /* Tell bufmgr and smgr to prepare for commit */ @@ -531,12 +532,29 @@ RecordTransactionCommit(void) START_CRIT_SECTION(); /* - * We only need to log the commit in xlog if the transaction made - * any transaction-controlled XLOG entries. (Otherwise, its XID - * appears nowhere in permanent storage, so no one else will ever - * care if it committed.) + * If our transaction made any transaction-controlled XLOG entries, + * we need to lock out checkpoint start between writing our XLOG + * record and updating pg_clog. Otherwise it is possible for the + * checkpoint to set REDO after the XLOG record but fail to flush the + * pg_clog update to disk, leading to loss of the transaction commit + * if we crash a little later. Slightly klugy fix for problem + * discovered 2004-08-10. + * + * (If it made no transaction-controlled XLOG entries, its XID + * appears nowhere in permanent storage, so no one else will ever care + * if it committed; so it doesn't matter if we lose the commit flag.) + * + * Note we only need a shared lock. */ - if (MyLastRecPtr.xrecoff != 0) + madeTCentries = (MyLastRecPtr.xrecoff != 0); + if (madeTCentries) + LWLockAcquire(CheckpointStartLock, LW_SHARED); + + /* + * We only need to log the commit in XLOG if the transaction made + * any transaction-controlled XLOG entries. + */ + if (madeTCentries) { /* Need to emit a commit record */ XLogRecData rdata; @@ -605,6 +623,10 @@ RecordTransactionCommit(void) if (MyLastRecPtr.xrecoff != 0 || MyXactMadeTempRelUpdate) TransactionIdCommit(xid); + /* Unlock checkpoint lock if we acquired it */ + if (madeTCentries) + LWLockRelease(CheckpointStartLock); + END_CRIT_SECTION(); } @@ -724,6 +746,8 @@ RecordTransactionAbort(void) * care if it committed.) We do not flush XLOG to disk in any * case, since the default assumption after a crash would be that * we aborted, anyway. + * For the same reason, we don't need to worry about interlocking + * against checkpoint start. */ if (MyLastRecPtr.xrecoff != 0) { diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index e4961af4307..a97f59490b3 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.109.2.3 2003/07/17 16:45:25 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.109.2.4 2004/08/11 04:08:39 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -2994,6 +2994,15 @@ CreateCheckPoint(bool shutdown, bool force) checkPoint.ThisStartUpID = ThisStartUpID; checkPoint.time = time(NULL); + /* + * We must hold CheckpointStartLock while determining the checkpoint + * REDO pointer. This ensures that any concurrent transaction commits + * will be either not yet logged, or logged and recorded in pg_clog. + * See notes in RecordTransactionCommit(). + */ + LWLockAcquire(CheckpointStartLock, LW_EXCLUSIVE); + + /* And we need WALInsertLock too */ LWLockAcquire(WALInsertLock, LW_EXCLUSIVE); /* @@ -3025,6 +3034,7 @@ CreateCheckPoint(bool shutdown, bool force) ControlFile->checkPointCopy.redo.xrecoff) { LWLockRelease(WALInsertLock); + LWLockRelease(CheckpointStartLock); LWLockRelease(CheckpointLock); END_CRIT_SECTION(); return; @@ -3091,11 +3101,13 @@ CreateCheckPoint(bool shutdown, bool force) #endif /* - * Now we can release insert lock, allowing other xacts to proceed - * even while we are flushing disk buffers. + * Now we can release insert lock and checkpoint start lock, allowing + * other xacts to proceed even while we are flushing disk buffers. */ LWLockRelease(WALInsertLock); + LWLockRelease(CheckpointStartLock); + /* * Get the other info we need for the checkpoint record. */ diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h index e061cd82b7e..f6e12a94885 100644 --- a/src/include/storage/lwlock.h +++ b/src/include/storage/lwlock.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: lwlock.h,v 1.6 2002/06/20 20:29:52 momjian Exp $ + * $Id: lwlock.h,v 1.6.2.1 2004/08/11 04:08:40 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -37,6 +37,7 @@ typedef enum LWLockId WALWriteLock, ControlFileLock, CheckpointLock, + CheckpointStartLock, CLogControlLock, RelCacheInitLock, |