Wait more time for writer gang

The mechanism of fork gang adopts the asynchronous mode,
Search for writer proc entry and retry only 5 times.
Waiting for a total of 5 * 2=10 milliseconds,
the writer process may not have started.
Add the guc parameter find_writer_proc_retry_time to control
the number of retries. When the fork gang takes a long time,
you can increase the parameters.

Author: kongfanhsen

src/backend/storage/lmgr/lock.c

@@ -330,6 +330,8 @@ static LOCALLOCK *StrongLockInProgress;
 LOCALLOCK *awaitedLock;
 ResourceOwner awaitedOwner;
 
+/* find writer proc entry retry time */
+int	find_writer_proc_retry_time = 5;
 
 #ifdef LOCK_DEBUG
 
@@ -938,7 +940,7 @@ LockAcquireExtended(const LOCKTAG *locktag,
 				/* Find the guy who should manage our locks */
 				volatile PGPROC * proc = FindProcByGpSessionId(gp_session_id);
 				int count = 0;
-				while(proc==NULL && count < 5)
+				while(proc==NULL && count < find_writer_proc_retry_time)
 				{
 					pg_usleep( /* microseconds */ 2000);
 					count++;

src/backend/utils/misc/guc.c

@@ -2652,6 +2652,16 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"find_writer_proc_retry_time", PGC_USERSET, DEVELOPER_OPTIONS,
+			gettext_noop("Sets the retry time of find writer proc entry."),
+			NULL
+		},
+		&find_writer_proc_retry_time,
+		5, 1, 5000,
+		NULL, NULL, NULL
+	},
+
 #ifdef LOCK_DEBUG
 	{
 		{"trace_lock_oidmin", PGC_SUSET, DEVELOPER_OPTIONS,

src/include/storage/lock.h

@@ -35,6 +35,7 @@ typedef struct PROC_QUEUE
 
 /* GUC variables */
 extern int	max_locks_per_xact;
+extern int	find_writer_proc_retry_time;
 
 #ifdef LOCK_DEBUG
 extern int	Trace_lock_oidmin;

src/include/utils/sync_guc_name.h

@@ -199,3 +199,4 @@
 		"wal_sender_timeout",
 		"work_mem",
 		"zero_damaged_pages",
+		"find_writer_proc_retry_time",