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Fix undefined behaviour in pulseaudio --start.

Browse source 
Don't call pthread_join() to join a thread from a different
process than the thread was created in. Doing so can lead to
undefined behaviour.

On OpenBSD, the symptom was a pulseaudio process with a single
thread waiting forever for other threads to join. Since that
process also held the autospawn lock, starting new pulseaudio
processes with --start kept failing. The problem was analyzed
with help from Philip Guenther.

This patch adds a pa_thread_free_nojoin() function which can
be used to free resources for a thread without a join, as
suggested by Tanu Kaskinen.

See https://bugs.freedesktop.org/show_bug.cgi?id=71738
This commit is contained in:
Stefan Sperling 2013-11-21 18:47:42 +01:00 • committed by Tanu Kaskinen
parent 303cff04eb
commit d8e2b3a78c
3 changed files with 16 additions and 1 deletions
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9
src/pulsecore/lock-autospawn.c
View file

@ -114,8 +114,15 @@ static void unref(bool after_fork) {
if (n_ref > 0)
return;
/* Join threads only in the process the new thread was created in
* to avoid undefined behaviour.
* POSIX.1-2008 XSH 2.9.2 Thread IDs: "applications should only assume
* that thread IDs are usable and unique within a single process." */
if (thread) {
pa_thread_free(thread);
if (after_fork)
pa_thread_free_nojoin(thread);
else
pa_thread_free(thread);
thread = NULL;
}