Add an Assert() to max_parallel_workers enforcement.

robertmhaas · robertmhaas · commit 6599c9ac3340 · 2017-04-11T13:03:44.000-04:00
To prevent future bugs along the lines of the one corrected by commit 8ff5186, or find any that remain in the current code, add an Assert() that the difference between parallel_register_count and parallel_terminate_count is in a sane range. Kuntal Ghosh, with considerable tidying-up by me, per a suggestion from Neha Khatri. Reviewed by Tomas Vondra. Discussion: http://postgr.es/m/CAFO0U+-E8yzchwVnvn5BeRDPgX2z9vZUxQ8dxx9c0XFGBC7N1Q@mail.gmail.com
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
@@ -971,6 +971,9 @@ RegisterDynamicBackgroundWorker(BackgroundWorker *worker,
 					 BackgroundWorkerData->parallel_terminate_count) >=
 		max_parallel_workers)
 	{
+		Assert(BackgroundWorkerData->parallel_register_count -
+			   BackgroundWorkerData->parallel_terminate_count <=
+			   MAX_PARALLEL_WORKER_LIMIT);
 		LWLockRelease(BackgroundWorkerLock);
 		return false;
 	}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
@@ -57,7 +57,7 @@
 #include "parser/scansup.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
-#include "postmaster/bgworker.h"
+#include "postmaster/bgworker_internals.h"
 #include "postmaster/bgwriter.h"
 #include "postmaster/postmaster.h"
 #include "postmaster/syslogger.h"
@@ -2713,7 +2713,7 @@ static struct config_int ConfigureNamesInt[] =
 			NULL
 		},
 		&max_parallel_workers_per_gather,
-		2, 0, 1024,
+		2, 0, MAX_PARALLEL_WORKER_LIMIT,
 		NULL, NULL, NULL
 	},
 
@@ -2723,7 +2723,7 @@ static struct config_int ConfigureNamesInt[] =
 			NULL
 		},
 		&max_parallel_workers,
-		8, 0, 1024,
+		8, 0, MAX_PARALLEL_WORKER_LIMIT,
 		NULL, NULL, NULL
 	},
 
diff --git a/src/include/postmaster/bgworker_internals.h b/src/include/postmaster/bgworker_internals.h
@@ -16,6 +16,13 @@
 #include "lib/ilist.h"
 #include "postmaster/bgworker.h"
 
+/* GUC options */
+
+/*
+ * Maximum possible value of parallel workers.
+ */
+#define MAX_PARALLEL_WORKER_LIMIT 1024
+
 /*
  * List of background workers, private to postmaster.
  *

Original file line number	Diff line number	Diff line change
`@@ -971,6 +971,9 @@ RegisterDynamicBackgroundWorker(BackgroundWorker *worker,`
`971`	`971`	`BackgroundWorkerData->parallel_terminate_count) >=`
`972`	`972`	`max_parallel_workers)`
`973`	`973`	`{`
	`974`	`+ Assert(BackgroundWorkerData->parallel_register_count -`
	`975`	`+ BackgroundWorkerData->parallel_terminate_count <=`
	`976`	`+ MAX_PARALLEL_WORKER_LIMIT);`
`974`	`977`	`LWLockRelease(BackgroundWorkerLock);`
`975`	`978`	`return false;`
`976`	`979`	`}`