diff options
Diffstat (limited to 'src/backend/access/transam/xlog.c')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 51 |
1 files changed, 17 insertions, 34 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 1e593a9c823..0af9d2910d4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.142 2004/05/21 16:08:46 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.143 2004/05/27 17:12:42 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -166,9 +166,10 @@ XLogRecPtr ProcLastRecEnd = {0, 0}; * XLogCtl->Insert.RedoRecPtr, whenever we can safely do so (ie, when we * hold the Insert lock). See XLogInsert for details. We are also allowed * to update from XLogCtl->Insert.RedoRecPtr if we hold the info_lck; - * see GetRedoRecPtr. + * see GetRedoRecPtr. A freshly spawned backend obtains the value during + * InitXLOGAccess. */ -NON_EXEC_STATIC XLogRecPtr RedoRecPtr; +static XLogRecPtr RedoRecPtr; /*---------- * Shared-memory data structures for XLOG control @@ -280,10 +281,6 @@ typedef struct XLogCtlData uint32 XLogCacheBlck; /* highest allocated xlog buffer index */ StartUpID ThisStartUpID; - /* This value is not protected by *any* lock... */ - /* see SetSavedRedoRecPtr/GetSavedRedoRecPtr */ - XLogRecPtr SavedRedoRecPtr; - slock_t info_lck; /* locks shared LogwrtRqst/LogwrtResult */ } XLogCtlData; @@ -2893,8 +2890,7 @@ StartupXLOG(void) else ThisStartUpID = checkPoint.ThisStartUpID; - RedoRecPtr = XLogCtl->Insert.RedoRecPtr = - XLogCtl->SavedRedoRecPtr = checkPoint.redo; + RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo; if (XLByteLT(RecPtr, checkPoint.redo)) ereport(PANIC, @@ -3251,35 +3247,22 @@ ReadCheckpointRecord(XLogRecPtr RecPtr, } /* - * Postmaster uses this to initialize ThisStartUpID & RedoRecPtr from - * XLogCtlData located in shmem after successful startup. + * This must be called during startup of a backend process, except that + * it need not be called in a standalone backend (which does StartupXLOG + * instead). We need to initialize the local copies of ThisStartUpID and + * RedoRecPtr. + * + * Note: before Postgres 7.5, we went to some effort to keep the postmaster + * process's copies of ThisStartUpID and RedoRecPtr valid too. This was + * unnecessary however, since the postmaster itself never touches XLOG anyway. */ void -SetThisStartUpID(void) +InitXLOGAccess(void) { + /* ThisStartUpID doesn't change so we need no lock to copy it */ ThisStartUpID = XLogCtl->ThisStartUpID; - RedoRecPtr = XLogCtl->SavedRedoRecPtr; -} - -/* - * CheckPoint process called by postmaster saves copy of new RedoRecPtr - * in shmem (using SetSavedRedoRecPtr). When checkpointer completes, - * postmaster calls GetSavedRedoRecPtr to update its own copy of RedoRecPtr, - * so that subsequently-spawned backends will start out with a reasonably - * up-to-date local RedoRecPtr. Since these operations are not protected by - * any lock and copying an XLogRecPtr isn't atomic, it's unsafe to use either - * of these routines at other times! - */ -void -SetSavedRedoRecPtr(void) -{ - XLogCtl->SavedRedoRecPtr = RedoRecPtr; -} - -void -GetSavedRedoRecPtr(void) -{ - RedoRecPtr = XLogCtl->SavedRedoRecPtr; + /* Use GetRedoRecPtr to copy the RedoRecPtr safely */ + (void) GetRedoRecPtr(); } /* |