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 6b2385c4711edabd65beafac8f9ef0d85be12b0b..9ad3e915db30efb5645be3f315fb585612a6a04d 100644 (file)
--- 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 6e39a676094c8402865fb306179ff18187344f14..9ad8361a9bd6a81bd2ea82c35992946b932528a1 100644 (file)
--- 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 9a2de4f4d04a991d73cce38c247501add2e5e800..9e0b0621cf4794ed25d1827a41b2586862b5b4be 100644 (file)
--- 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.
  *