From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 11 Apr 2017 17:03:44 +0000 (-0400)
Subject: Add an Assert() to max_parallel_workers enforcement.
X-Git-Tag: REL_10_BETA1~299
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=6599c9ac3340b6cd3d86a0a7f866b80a009fecab;p=postgresql

Add an Assert() to max_parallel_workers enforcement.

To prevent future bugs along the lines of the one corrected by commit
8ff518699f19dd0a5076f5090bac8400b8233f7f, 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
index 6b2385c471..9ad3e915db 100644
--- 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
index 6e39a67609..9ad8361a9b 100644
--- 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
index 9a2de4f4d0..9e0b0621cf 100644
--- 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.
  *