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On Darwin, detect and report a multithreaded postmaster.

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Darwin --enable-nls builds use a substitute setlocale() that may start a
thread.  Buildfarm member orangutan experienced BackendList corruption
on account of different postmaster threads executing signal handlers
simultaneously.  Furthermore, a multithreaded postmaster risks undefined
behavior from sigprocmask() and fork().  Emit LOG messages about the
problem and its workaround.  Back-patch to 9.0 (all supported versions).
This commit is contained in:
Noah Misch
2015-01-07 22:35:44 -05:00
parent 6fdba8ceb0
commit 894459e59f
5 changed files with 60 additions and 2 deletions
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43
src/backend/postmaster/postmaster.c
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@@ -87,6 +87,10 @@
#include <dns_sd.h>
#endif
#ifdef HAVE_PTHREAD_IS_THREADED_NP
#include <pthread.h>
#endif
#include "access/transam.h"
#include "access/xlog.h"
#include "bootstrap/bootstrap.h"
@@ -1200,6 +1204,24 @@ PostmasterMain(int argc, char *argv[])
*/
RemovePgTempFiles();
#ifdef HAVE_PTHREAD_IS_THREADED_NP
/*
* On Darwin, libintl replaces setlocale() with a version that calls
* CFLocaleCopyCurrent() when its second argument is "" and every relevant
* environment variable is unset or empty. CFLocaleCopyCurrent() makes
* the process multithreaded. The postmaster calls sigprocmask() and
* calls fork() without an immediate exec(), both of which have undefined
* behavior in a multithreaded program. A multithreaded postmaster is the
* normal case on Windows, which offers neither fork() nor sigprocmask().
*/
if (pthread_is_threaded_np() != 0)
ereport(LOG,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("postmaster became multithreaded during startup"),
errhint("Set the LC_ALL environment variable to a valid locale.")));
#endif
/*
* Remember postmaster startup time
*/
@@ -1657,6 +1679,15 @@ ServerLoop(void)
last_touch_time = now;
}
#ifdef HAVE_PTHREAD_IS_THREADED_NP
/*
* With assertions enabled, check regularly for appearance of
* additional threads. All builds check at start and exit.
*/
Assert(pthread_is_threaded_np() == 0);
#endif
/*
* If we already sent SIGQUIT to children and they are slow to shut
* down, it's time to send them SIGKILL. This doesn't happen
@@ -4745,6 +4776,18 @@ SubPostmasterMain(int argc, char *argv[])
static void
ExitPostmaster(int status)
{
#ifdef HAVE_PTHREAD_IS_THREADED_NP
/*
* There is no known cause for a postmaster to become multithreaded after
* startup. Recheck to account for the possibility of unknown causes.
*/
if (pthread_is_threaded_np() != 0)
ereport(LOG,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("postmaster became multithreaded")));
#endif
/* should cleanup shared memory and kill all backends */
/*