From 2d7a958ca586c5f767a7800f99dbe11b76ee69e3 Mon Sep 17 00:00:00 2001 From: jasone Date: Sun, 19 Aug 2001 20:05:42 +0000 Subject: Fix logic errors in pthread_cond_wait() and pthread_cond_timedwait() that could cause deadlock after interruption due to a signal. Reviewed by: deischen --- lib/libpthread/thread/thr_cond.c | 120 +++++++++++++++++---------------------- 1 file changed, 52 insertions(+), 68 deletions(-) (limited to 'lib/libpthread/thread') diff --git a/lib/libpthread/thread/thr_cond.c b/lib/libpthread/thread/thr_cond.c index ea8215d..7f3fe7a 100644 --- a/lib/libpthread/thread/thr_cond.c +++ b/lib/libpthread/thread/thr_cond.c @@ -170,7 +170,6 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) int rval = 0; int done = 0; int interrupted = 0; - int unlock_mutex = 1; int seqno; _thread_enter_cancellation_point(); @@ -238,8 +237,7 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) curthread->wakeup_time.tv_sec = -1; /* Unlock the mutex: */ - if ((unlock_mutex != 0) && - ((rval = _mutex_cv_unlock(mutex)) != 0)) { + if ((rval = _mutex_cv_unlock(mutex)) != 0) { /* * Cannot unlock the mutex, so remove * the running thread from the condition @@ -254,15 +252,7 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) /* Unlock the condition variable structure: */ _SPINUNLOCK(&(*cond)->lock); - } - else { - /* - * Don't unlock the mutex in the event - * this thread has to be requeued in - * condition variable queue: - */ - unlock_mutex = 0; - + } else { /* * Schedule the next thread and unlock * the condition variable structure: @@ -272,8 +262,24 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) done = (seqno != (*cond)->c_seqno); - if ((curthread->flags & - PTHREAD_FLAGS_IN_CONDQ) != 0) { + interrupted = curthread->interrupted; + + /* + * Check if the wait was interrupted + * (canceled) or needs to be resumed + * after handling a signal. + */ + if (interrupted != 0) { + /* + * Lock the mutex and ignore any + * errors. Note that even + * though this thread may have + * been canceled, POSIX requires + * that the mutex be reaquired + * prior to cancellation. + */ + (void)_mutex_cv_lock(mutex); + } else { /* * Lock the condition variable * while removing the thread. @@ -288,20 +294,10 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) (*cond)->c_mutex = NULL; _SPINUNLOCK(&(*cond)->lock); - } - - /* - * Save the interrupted flag; locking - * the mutex will destroy it. - */ - interrupted = curthread->interrupted; - /* - * Note that even though this thread may have - * been canceled, POSIX requires that the mutex - * be reaquired prior to cancellation. - */ - rval = _mutex_cv_lock(mutex); + /* Lock the mutex: */ + rval = _mutex_cv_lock(mutex); + } } } break; @@ -334,7 +330,6 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, int rval = 0; int done = 0; int interrupted = 0; - int unlock_mutex = 1; int seqno; _thread_enter_cancellation_point(); @@ -404,8 +399,7 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, seqno = (*cond)->c_seqno; /* Unlock the mutex: */ - if ((unlock_mutex != 0) && - ((rval = _mutex_cv_unlock(mutex)) != 0)) { + if ((rval = _mutex_cv_unlock(mutex)) != 0) { /* * Cannot unlock the mutex, so remove * the running thread from the condition @@ -421,13 +415,6 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, _SPINUNLOCK(&(*cond)->lock); } else { /* - * Don't unlock the mutex in the event - * this thread has to be requeued in - * condition variable queue: - */ - unlock_mutex = 0; - - /* * Schedule the next thread and unlock * the condition variable structure: */ @@ -436,25 +423,30 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, done = (seqno != (*cond)->c_seqno); + interrupted = curthread->interrupted; + /* - * Check if the wait timedout, was - * interrupted (canceled), or needs to - * be resumed after handling a signal. + * Check if the wait was interrupted + * (canceled) or needs to be resumed + * after handling a signal. */ - if ((curthread->timeout == 0) && - (curthread->interrupted == 0) && - (done != 0)) { - /* Lock the mutex: */ - rval = _mutex_cv_lock(mutex); + if (interrupted != 0) { + /* + * Lock the mutex and ignore any + * errors. Note that even + * though this thread may have + * been canceled, POSIX requires + * that the mutex be reaquired + * prior to cancellation. + */ + (void)_mutex_cv_lock(mutex); } else { - /* Lock the CV structure: */ - _SPINLOCK(&(*cond)->lock); - /* - * The wait timed out; remove - * the thread from the condition - * variable queue: + * Lock the condition variable + * while removing the thread. */ + _SPINLOCK(&(*cond)->lock); + cond_queue_remove(*cond, curthread); @@ -462,28 +454,20 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, if (TAILQ_FIRST(&(*cond)->c_queue) == NULL) (*cond)->c_mutex = NULL; - /* Unock the CV structure: */ _SPINUNLOCK(&(*cond)->lock); - /* Return a timeout error: */ - if (curthread->timeout != 0) - rval = ETIMEDOUT; - /* - * Save the interrupted flag; - * locking the mutex will - * destroy it. - */ - interrupted = curthread->interrupted; + /* Lock the mutex: */ + rval = _mutex_cv_lock(mutex); /* - * Lock the mutex and ignore any - * errors. Note that even though - * this thread may have been - * canceled, POSIX requires that - * the mutex be reaquired prior - * to cancellation. + * Return ETIMEDOUT if the wait + * timed out and there wasn't an + * error locking the mutex: */ - (void)_mutex_cv_lock(mutex); + if ((curthread->timeout != 0) + && rval == 0) + rval = ETIMEDOUT; + } } } -- cgit v1.1