Don't call elog() while holding spinlock.

MasaoFujii · MasaoFujii · commit caa3c4242cf8 · 2020-06-02T19:21:04.000+09:00
Previously UpdateSpillStats() called elog(DEBUG2) while holding the spinlock even though the local variables that the elog() accesses don't need to be protected by the lock. Since spinlocks are intended for very short-term locks, they should not be used when calling elog(DEBUG2). So this commit moves that elog() out of spinlock period. Author: Kyotaro Horiguchi Reviewed-by: Amit Kapila and Fujii Masao Discussion: https://postgr.es/m/20200602.161518.1399689010416646074.horikyota.ntt@gmail.com
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
@@ -3685,17 +3685,15 @@ UpdateSpillStats(LogicalDecodingContext *ctx)
 {
 	ReorderBuffer *rb = ctx->reorder;
 
-	SpinLockAcquire(&MyWalSnd->mutex);
-
-	MyWalSnd->spillTxns = rb->spillTxns;
-	MyWalSnd->spillCount = rb->spillCount;
-	MyWalSnd->spillBytes = rb->spillBytes;
-
 	elog(DEBUG2, "UpdateSpillStats: updating stats %p %lld %lld %lld",
 		 rb,
 		 (long long) rb->spillTxns,
 		 (long long) rb->spillCount,
 		 (long long) rb->spillBytes);
 
+	SpinLockAcquire(&MyWalSnd->mutex);
+	MyWalSnd->spillTxns = rb->spillTxns;
+	MyWalSnd->spillCount = rb->spillCount;
+	MyWalSnd->spillBytes = rb->spillBytes;
 	SpinLockRelease(&MyWalSnd->mutex);
 }
