diff options
Diffstat (limited to 'lib/libthr/thread/thr_exit.c')
| -rw-r--r-- | lib/libthr/thread/thr_exit.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/lib/libthr/thread/thr_exit.c b/lib/libthr/thread/thr_exit.c index 8c4a060..dd510b1 100644 --- a/lib/libthr/thread/thr_exit.c +++ b/lib/libthr/thread/thr_exit.c @@ -94,7 +94,7 @@ _thread_exit_cleanup(void) void _pthread_exit(void *status) { - pthread_t pthread; + pthread_t pthread, joiner; int exitNow = 0; /* Check if this thread is already in the process of exiting: */ @@ -122,10 +122,27 @@ _pthread_exit(void *status) _thread_cleanupspecific(); } +retry: + /* + * Proper lock order, to minimize deadlocks, between joining + * and exiting threads is: DEAD_LIST, THREAD_LIST, exiting, joiner. + * In order to do this *and* protect from races, we must resort + * this test-and-retry loop. + */ + joiner = curthread->joiner; + /* Lock the dead list first to maintain correct lock order */ DEAD_LIST_LOCK; + THREAD_LIST_LOCK; _thread_critical_enter(curthread); + if (joiner != curthread->joiner) { + _thread_critical_exit(curthread); + THREAD_LIST_UNLOCK; + DEAD_LIST_UNLOCK; + goto retry; + } + /* Check if there is a thread joining this one: */ if (curthread->joiner != NULL) { pthread = curthread->joiner; @@ -151,7 +168,6 @@ _pthread_exit(void *status) * Add this thread to the list of dead threads, and * also remove it from the active threads list. */ - THREAD_LIST_LOCK; TAILQ_INSERT_HEAD(&_dead_list, curthread, dle); TAILQ_REMOVE(&_thread_list, curthread, tle); PTHREAD_SET_STATE(curthread, PS_DEAD); |
