Fix failure in CreateCheckPoint on some Alpha boxes --- it's not OK to

assume that TAS() will always succeed the first time, even if the lock
is known to be free.  Also, make sure that code will eventually time out
and report a stuck spinlock, rather than looping forever.  Small cleanups
in s_lock.h, too.

1 files changed, 27 insertions, 55 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 7294b97ff34..ff8916cd37b 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.45 2000/12/28 13:00:08 vadim Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.46 2000/12/29 21:31:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -411,7 +411,7 @@ begin:;
 					}
 				}
 			}
-			s_lock_sleep(i++);
+			S_LOCK_SLEEP(&(XLogCtl->insert_lck), i++);
 			if (!TAS(&(XLogCtl->insert_lck)))
 				break;
 		}
@@ -599,17 +599,10 @@ begin:;
 
 	if (updrqst)
 	{
-		for (;;)
-		{
-			if (!TAS(&(XLogCtl->info_lck)))
-			{
-				if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrRqst.Write))
-					XLogCtl->LgwrRqst.Write = LgwrRqst.Write;
-				S_UNLOCK(&(XLogCtl->info_lck));
-				break;
-			}
-			s_lock_sleep(i++);
-		}
+		S_LOCK(&(XLogCtl->info_lck));
+		if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrRqst.Write))
+			XLogCtl->LgwrRqst.Write = LgwrRqst.Write;
+		S_UNLOCK(&(XLogCtl->info_lck));
 	}
 
 	END_CRIT_CODE;
@@ -622,7 +615,7 @@ XLogFlush(XLogRecPtr record)
 	XLogRecPtr	WriteRqst;
 	char		buffer[BLCKSZ];
 	char	   *usebuf = NULL;
-	unsigned	i = 0;
+	unsigned	spins = 0;
 	bool		force_lgwr = false;
 
 	if (XLOG_DEBUG)
@@ -715,7 +708,7 @@ XLogFlush(XLogRecPtr record)
 				break;
 			}
 		}
-		s_lock_sleep(i++);
+		S_LOCK_SLEEP(&(XLogCtl->lgwr_lck), spins++);
 	}
 
 	if (logFile >= 0 && (LgwrResult.Write.xlogid != logId ||
@@ -740,18 +733,12 @@ XLogFlush(XLogRecPtr record)
 			 logId, logSeg);
 	LgwrResult.Flush = LgwrResult.Write;
 
-	for (i = 0;;)
-	{
-		if (!TAS(&(XLogCtl->info_lck)))
-		{
-			XLogCtl->LgwrResult = LgwrResult;
-			if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
-				XLogCtl->LgwrRqst.Write = LgwrResult.Write;
-			S_UNLOCK(&(XLogCtl->info_lck));
-			break;
-		}
-		s_lock_sleep(i++);
-	}
+	S_LOCK(&(XLogCtl->info_lck));
+	XLogCtl->LgwrResult = LgwrResult;
+	if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
+		XLogCtl->LgwrRqst.Write = LgwrResult.Write;
+	S_UNLOCK(&(XLogCtl->info_lck));
+
 	XLogCtl->Write.LgwrResult = LgwrResult;
 
 	S_UNLOCK(&(XLogCtl->lgwr_lck));
@@ -767,6 +754,7 @@ GetFreeXLBuffer()
 	XLogCtlInsert *Insert = &XLogCtl->Insert;
 	XLogCtlWrite *Write = &XLogCtl->Write;
 	uint16		curridx = NextBufIdx(Insert->curridx);
+	unsigned	spins = 0;
 
 	LgwrRqst.Write = XLogCtl->xlblocks[Insert->curridx];
 	for (;;)
@@ -809,9 +797,8 @@ GetFreeXLBuffer()
 			InitXLBuffer(curridx);
 			return;
 		}
+		S_LOCK_SLEEP(&(XLogCtl->lgwr_lck), spins++);
 	}
-
-	return;
 }
 
 static void
@@ -820,7 +807,6 @@ XLogWrite(char *buffer)
 	XLogCtlWrite *Write = &XLogCtl->Write;
 	char	   *from;
 	uint32		wcnt = 0;
-	int			i = 0;
 	bool		usexistent;
 
 	for (; XLByteLT(LgwrResult.Write, LgwrRqst.Write);)
@@ -919,18 +905,12 @@ XLogWrite(char *buffer)
 		LgwrResult.Flush = LgwrResult.Write;
 	}
 
-	for (;;)
-	{
-		if (!TAS(&(XLogCtl->info_lck)))
-		{
-			XLogCtl->LgwrResult = LgwrResult;
-			if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
-				XLogCtl->LgwrRqst.Write = LgwrResult.Write;
-			S_UNLOCK(&(XLogCtl->info_lck));
-			break;
-		}
-		s_lock_sleep(i++);
-	}
+	S_LOCK(&(XLogCtl->info_lck));
+	XLogCtl->LgwrResult = LgwrResult;
+	if (XLByteLT(XLogCtl->LgwrRqst.Write, LgwrResult.Write))
+		XLogCtl->LgwrRqst.Write = LgwrResult.Write;
+	S_UNLOCK(&(XLogCtl->info_lck));
+
 	Write->LgwrResult = LgwrResult;
 }
 
@@ -2062,18 +2042,17 @@ CreateCheckPoint(bool shutdown)
 	uint32		_logId;
 	uint32		_logSeg;
 	char		archdir[MAXPGPATH];
+	unsigned	spins = 0;
 
 	if (MyLastRecPtr.xrecoff != 0)
 		elog(ERROR, "CreateCheckPoint: cannot be called inside transaction block");
  
 	START_CRIT_CODE;
+
+	/* Grab lock, using larger than normal sleep between tries (1 sec) */
 	while (TAS(&(XLogCtl->chkp_lck)))
 	{
-		struct timeval delay = {2, 0};
-
-		if (shutdown)
-			elog(STOP, "Checkpoint lock is busy while data base is shutting down");
-		(void) select(0, NULL, NULL, NULL, &delay);
+		S_LOCK_SLEEP_INTERVAL(&(XLogCtl->chkp_lck), spins++, 1000000);
 	}
 
 	memset(&checkPoint, 0, sizeof(checkPoint));
@@ -2087,14 +2066,7 @@ CreateCheckPoint(bool shutdown)
 	checkPoint.Shutdown = shutdown;
 
 	/* Get REDO record ptr */
-	while (TAS(&(XLogCtl->insert_lck)))
-	{
-		struct timeval delay = {1, 0};
-
-		if (shutdown)
-			elog(STOP, "XLog insert lock is busy while data base is shutting down");
-		(void) select(0, NULL, NULL, NULL, &delay);
-	}
+	S_LOCK(&(XLogCtl->insert_lck));
 	freespace = ((char *) Insert->currpage) + BLCKSZ - Insert->currpos;
 	if (freespace < SizeOfXLogRecord)
 	{