From 3a024859a420780da37a7c1927e0356a25874174 Mon Sep 17 00:00:00 2001 From: Stefan Sperling Date: Thu, 21 Nov 2013 18:47:42 +0100 Subject: [PATCH] Fix undefined behaviour in pulseaudio --start. 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 --- src/pulsecore/lock-autospawn.c | 9 ++++++++- src/pulsecore/thread-posix.c | 7 +++++++ src/pulsecore/thread.h | 1 + 3 files changed, 16 insertions(+), 1 deletion(-) diff --git a/src/pulsecore/lock-autospawn.c b/src/pulsecore/lock-autospawn.c index 72806f8..82518db 100644 --- a/src/pulsecore/lock-autospawn.c +++ b/src/pulsecore/lock-autospawn.c @@ -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; } diff --git a/src/pulsecore/thread-posix.c b/src/pulsecore/thread-posix.c index b422ab0..5c19b43 100644 --- a/src/pulsecore/thread-posix.c +++ b/src/pulsecore/thread-posix.c @@ -127,6 +127,13 @@ void pa_thread_free(pa_thread *t) { pa_xfree(t); } +void pa_thread_free_nojoin(pa_thread *t) { + pa_assert(t); + + pa_xfree(t->name); + pa_xfree(t); +} + int pa_thread_join(pa_thread *t) { pa_assert(t); pa_assert(t->thread_func); diff --git a/src/pulsecore/thread.h b/src/pulsecore/thread.h index 9cabb89..a6e5f42 100644 --- a/src/pulsecore/thread.h +++ b/src/pulsecore/thread.h @@ -39,6 +39,7 @@ typedef void (*pa_thread_func_t) (void *userdata); pa_thread* pa_thread_new(const char *name, pa_thread_func_t thread_func, void *userdata); void pa_thread_free(pa_thread *t); +void pa_thread_free_nojoin(pa_thread *t); int pa_thread_join(pa_thread *t); int pa_thread_is_running(pa_thread *t); pa_thread *pa_thread_self(void); -- 1.8.4.3