diff options
Diffstat (limited to 'src/backend/access/transam/xact.c')
| -rw-r--r-- | src/backend/access/transam/xact.c | 48 |
1 files changed, 25 insertions, 23 deletions
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index f8058a8f5e9..d47dae0c412 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -10,7 +10,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.238 2007/03/22 19:55:04 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.239 2007/04/03 16:34:35 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -717,34 +717,36 @@ RecordTransactionCommit(void) START_CRIT_SECTION(); /* - * 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. - */ - 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 or will delete files. */ + madeTCentries = (MyLastRecPtr.xrecoff != 0); if (madeTCentries || nrels > 0) { XLogRecData rdata[3]; int lastrdata = 0; xl_xact_commit xlrec; + /* + * Mark ourselves as within our "commit critical section". This + * forces any concurrent checkpoint to wait until we've updated + * pg_clog. Without this, 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 + * the system crashes a little later. + * + * Note: we could, but don't bother to, set this flag in + * RecordTransactionAbort. That's because loss of a transaction + * abort is noncritical; the presumption would be that it aborted, + * anyway. + * + * It's safe to change the inCommit flag of our own backend + * without holding the ProcArrayLock, since we're the only one + * modifying it. This makes checkpoint's determination of which + * xacts are inCommit a bit fuzzy, but it doesn't matter. + */ + MyProc->inCommit = true; + xlrec.xtime = time(NULL); xlrec.nrels = nrels; xlrec.nsubxacts = nchildren; @@ -825,9 +827,8 @@ RecordTransactionCommit(void) TransactionIdCommitTree(nchildren, children); } - /* Unlock checkpoint lock if we acquired it */ - if (madeTCentries) - LWLockRelease(CheckpointStartLock); + /* Checkpoint can proceed now */ + MyProc->inCommit = false; END_CRIT_SECTION(); } @@ -1961,6 +1962,7 @@ AbortTransaction(void) MyProc->xid = InvalidTransactionId; MyProc->xmin = InvalidTransactionId; MyProc->inVacuum = false; /* must be cleared with xid/xmin */ + MyProc->inCommit = false; /* be sure this gets cleared */ /* Clear the subtransaction-XID cache too while holding the lock */ MyProc->subxids.nxids = 0; |