From b487979a362f90b866a86b1600791178b5574a75 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Fri, 29 Jan 2021 22:34:58 -0300 Subject: [PATCH v2 3/3] add barriers --- src/backend/access/transam/xlog.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 8073a92ceb..458efc5a55 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -1169,6 +1169,8 @@ XLogInsertRecord(XLogRecData *rdata, { /* advance global request to include new block(s) */ pg_atomic_monotonic_advance_u64(&XLogCtl->LogwrtRqst.Write, EndPos); + pg_memory_barrier(); + /* update local result copy */ LogwrtResult.Write = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Write); LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); @@ -2165,6 +2167,7 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, bool opportunistic) /* Before waiting, update LogwrtResult */ pg_atomic_monotonic_advance_u64(&XLogCtl->LogwrtRqst.Write, OldPageRqstPtr); + pg_memory_barrier(); LogwrtResult.Write = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Write); LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); @@ -2678,6 +2681,7 @@ XLogWrite(XLogwrt WriteRqst, bool flexible) pg_atomic_monotonic_advance_u64(&XLogCtl->LogwrtRqst.Write, LogwrtResult.Write); pg_atomic_monotonic_advance_u64(&XLogCtl->LogwrtRqst.Flush, LogwrtResult.Flush); + pg_write_barrier(); } } @@ -2905,6 +2909,7 @@ XLogFlush(XLogRecPtr record) WriteRqstPtr = pg_atomic_read_u64(&XLogCtl->LogwrtRqst.Write); LogwrtResult.Write = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Write); LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); + pg_read_barrier(); /* done already? */ if (record <= LogwrtResult.Flush) @@ -2936,6 +2941,7 @@ XLogFlush(XLogRecPtr record) /* Got the lock; recheck whether request is satisfied */ LogwrtResult.Write = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Write); LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); + pg_read_barrier(); if (record <= LogwrtResult.Flush) { LWLockRelease(WALWriteLock); @@ -3055,6 +3061,7 @@ XLogBackgroundFlush(void) LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); WriteRqst.Write = pg_atomic_read_u64(&XLogCtl->LogwrtRqst.Write); WriteRqst.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtRqst.Flush); + pg_read_barrier(); /* back off to last completed page boundary */ WriteRqst.Write -= WriteRqst.Write % XLOG_BLCKSZ; @@ -3138,6 +3145,7 @@ XLogBackgroundFlush(void) LWLockAcquire(WALWriteLock, LW_EXCLUSIVE); LogwrtResult.Write = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Write); LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); + pg_read_barrier(); if (WriteRqst.Write > LogwrtResult.Write || WriteRqst.Flush > LogwrtResult.Flush) { @@ -3227,6 +3235,7 @@ XLogNeedsFlush(XLogRecPtr record) /* read LogwrtResult and update local state */ LogwrtResult.Write = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Write); LogwrtResult.Flush = pg_atomic_read_u64(&XLogCtl->LogwrtResult.Flush); + pg_read_barrier(); /* check again */ if (record <= LogwrtResult.Flush) @@ -7780,6 +7789,7 @@ StartupXLOG(void) pg_atomic_write_u64(&XLogCtl->LogwrtRqst.Write, EndOfLog); pg_atomic_write_u64(&XLogCtl->LogwrtRqst.Flush, EndOfLog); + pg_write_barrier(); /* * Update full_page_writes in shared memory and write an XLOG_FPW_CHANGE -- 2.20.1