diff options
Diffstat (limited to 'src/backend/replication/syncrep.c')
| -rw-r--r-- | src/backend/replication/syncrep.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c index 32db2bc4c52..56af4237e80 100644 --- a/src/backend/replication/syncrep.c +++ b/src/backend/replication/syncrep.c @@ -166,13 +166,6 @@ SyncRepWaitForLSN(XLogRecPtr XactCommitLSN) { int syncRepState; - /* - * Wait on latch for up to 60 seconds. This allows us to check for - * postmaster death regularly while waiting. Note that timeout here - * does not necessarily release from loop. - */ - WaitLatch(&MyProc->waitLatch, WL_LATCH_SET | WL_TIMEOUT, 60000000L); - /* Must reset the latch before testing state. */ ResetLatch(&MyProc->waitLatch); @@ -184,6 +177,12 @@ SyncRepWaitForLSN(XLogRecPtr XactCommitLSN) * walsender changes the state to SYNC_REP_WAIT_COMPLETE, it will * never update it again, so we can't be seeing a stale value in that * case. + * + * Note: on machines with weak memory ordering, the acquisition of + * the lock is essential to avoid race conditions: we cannot be sure + * the sender's state update has reached main memory until we acquire + * the lock. We could get rid of this dance if SetLatch/ResetLatch + * contained memory barriers. */ syncRepState = MyProc->syncRepState; if (syncRepState == SYNC_REP_WAITING) @@ -246,6 +245,13 @@ SyncRepWaitForLSN(XLogRecPtr XactCommitLSN) SyncRepCancelWait(); break; } + + /* + * Wait on latch for up to 60 seconds. This allows us to check for + * cancel/die signal or postmaster death regularly while waiting. Note + * that timeout here does not necessarily release from loop. + */ + WaitLatch(&MyProc->waitLatch, WL_LATCH_SET | WL_TIMEOUT, 60000000L); } /* |