diff options
Diffstat (limited to 'src/backend/access/transam/xact.c')
| -rw-r--r-- | src/backend/access/transam/xact.c | 36 |
1 files changed, 30 insertions, 6 deletions
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index e6767d4c4b1..3409de03a56 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 1.156 2003/10/16 16:50:41 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.156.2.1 2004/08/11 04:08:00 tgl Exp $ * * NOTES * Transaction aborts can now occur two ways: @@ -503,6 +503,7 @@ RecordTransactionCommit(void) if (MyXactMadeXLogEntry || MyXactMadeTempRelUpdate) { TransactionId xid = GetCurrentTransactionId(); + bool madeTCentries; XLogRecPtr recptr; /* Tell bufmgr and smgr to prepare for commit */ @@ -511,12 +512,29 @@ 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; @@ -585,6 +603,10 @@ RecordTransactionCommit(void) if (MyLastRecPtr.xrecoff != 0 || MyXactMadeTempRelUpdate) TransactionIdCommit(xid); + /* Unlock checkpoint lock if we acquired it */ + if (madeTCentries) + LWLockRelease(CheckpointStartLock); + END_CRIT_SECTION(); } @@ -698,6 +720,8 @@ 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) { |