From fd048e0cb5aa45ef67b5b2b0446f4b1b6bdefbf3 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 24 Oct 2020 13:12:08 -0400 Subject: [PATCH] Fix ancient bug in ecpg's pthread_once() emulation for Windows. We must not set the "done" flag until after we've executed the initialization function. Otherwise, other threads can fall through the initial unlocked test before initialization is really complete. This has been seen to cause rare failures of ecpg's thread/descriptor test, and it could presumably cause other sorts of misbehavior in threaded ECPG-using applications, since ecpglib relies on pthread_once() in several places. Diagnosis and patch by me, based on investigation by Alexander Lakhin. Back-patch to all supported branches (the bug dates to 2007). Discussion: https://postgr.es/m/16685-d6cd241872c101d3@postgresql.org --- src/interfaces/ecpg/ecpglib/misc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/interfaces/ecpg/ecpglib/misc.c b/src/interfaces/ecpg/ecpglib/misc.c index a07d0dfb9f..1feb5c03e1 100644 --- a/src/interfaces/ecpg/ecpglib/misc.c +++ b/src/interfaces/ecpg/ecpglib/misc.c @@ -477,8 +477,8 @@ win32_pthread_once(volatile pthread_once_t *once, void (*fn) (void)) pthread_mutex_lock(&win32_pthread_once_lock); if (!*once) { - *once = true; fn(); + *once = true; } pthread_mutex_unlock(&win32_pthread_once_lock); }