From: Tom Lane Date: Sat, 24 Oct 2020 17:12:08 +0000 (-0400) Subject: Fix ancient bug in ecpg's pthread_once() emulation for Windows. X-Git-Tag: REL_12_5~36 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bdc79ddd10790fcbaecc92e9ac3a64caa44d71e1;p=thirdparty%2Fpostgresql.git 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 --- diff --git a/src/interfaces/ecpg/ecpglib/misc.c b/src/interfaces/ecpg/ecpglib/misc.c index 2eec54a2d99..a51dc619a2a 100644 --- a/src/interfaces/ecpg/ecpglib/misc.c +++ b/src/interfaces/ecpg/ecpglib/misc.c @@ -482,8 +482,8 @@ 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); }