diff options
Diffstat (limited to 'lib/libpthread/thread/thr_cond.c')
| -rw-r--r-- | lib/libpthread/thread/thr_cond.c | 220 |
1 files changed, 118 insertions, 102 deletions
diff --git a/lib/libpthread/thread/thr_cond.c b/lib/libpthread/thread/thr_cond.c index fd7b6d9..cd719d4 100644 --- a/lib/libpthread/thread/thr_cond.c +++ b/lib/libpthread/thread/thr_cond.c @@ -47,6 +47,9 @@ static inline struct pthread *cond_queue_deq(pthread_cond_t); static inline void cond_queue_remove(pthread_cond_t, pthread_t); static inline void cond_queue_enq(pthread_cond_t, pthread_t); +static void cond_wait_backout(void *); +static inline void check_continuation(struct pthread *, + struct pthread_cond *, pthread_mutex_t *); /* * Double underscore versions are cancellation points. Single underscore @@ -171,8 +174,7 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) struct pthread *curthread = _get_curthread(); int rval = 0; int done = 0; - int interrupted = 0; - int unlock_mutex = 1; + int mutex_locked = 1; int seqno; if (cond == NULL) @@ -198,10 +200,11 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) * and backed out of the waiting queue prior to executing the * signal handler. */ - do { - /* Lock the condition variable structure: */ - THR_LOCK_ACQUIRE(curthread, &(*cond)->c_lock); + /* Lock the condition variable structure: */ + THR_LOCK_ACQUIRE(curthread, &(*cond)->c_lock); + seqno = (*cond)->c_seqno; + do { /* * If the condvar was statically allocated, properly * initialize the tail queue. @@ -217,9 +220,6 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) case COND_TYPE_FAST: if ((mutex == NULL) || (((*cond)->c_mutex != NULL) && ((*cond)->c_mutex != *mutex))) { - /* Unlock the condition variable structure: */ - THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); - /* Return invalid argument error: */ rval = EINVAL; } else { @@ -233,15 +233,11 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) */ cond_queue_enq(*cond, curthread); - /* Remember the mutex and sequence number: */ - (*cond)->c_mutex = *mutex; - seqno = (*cond)->c_seqno; - /* Wait forever: */ curthread->wakeup_time.tv_sec = -1; /* Unlock the mutex: */ - if ((unlock_mutex != 0) && + if (mutex_locked && ((rval = _mutex_cv_unlock(mutex)) != 0)) { /* * Cannot unlock the mutex, so remove @@ -249,22 +245,18 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) * variable queue: */ cond_queue_remove(*cond, curthread); - - /* Check for no more waiters: */ - if (TAILQ_FIRST(&(*cond)->c_queue) == NULL) - (*cond)->c_mutex = NULL; - - /* Unlock the condition variable structure: */ - THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); } else { + /* Remember the mutex: */ + (*cond)->c_mutex = *mutex; + /* * Don't unlock the mutex the next * time through the loop (if the * thread has to be requeued after * handling a signal). */ - unlock_mutex = 0; + mutex_locked = 0; /* * This thread is active and is in a @@ -277,6 +269,7 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) /* Remember the CV: */ curthread->data.cond = *cond; + curthread->sigbackout = cond_wait_backout; THR_SCHED_UNLOCK(curthread, curthread); /* Unlock the CV structure: */ @@ -286,8 +279,6 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) /* Schedule the next thread: */ _thr_sched_switch(curthread); - curthread->data.cond = NULL; - /* * XXX - This really isn't a good check * since there can be more than one @@ -299,41 +290,39 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) * should be sent "as soon as possible". */ done = (seqno != (*cond)->c_seqno); - - if (THR_IN_SYNCQ(curthread)) { + if (done && !THR_IN_CONDQ(curthread)) { /* - * Lock the condition variable - * while removing the thread. + * The thread is dequeued, so + * it is safe to clear these. */ - THR_LOCK_ACQUIRE(curthread, - &(*cond)->c_lock); + curthread->data.cond = NULL; + curthread->sigbackout = NULL; + check_continuation(curthread, + NULL, mutex); + return (_mutex_cv_lock(mutex)); + } + + /* Relock the CV structure: */ + THR_LOCK_ACQUIRE(curthread, + &(*cond)->c_lock); + + /* + * Clear these after taking the lock to + * prevent a race condition where a + * signal can arrive before dequeueing + * the thread. + */ + curthread->data.cond = NULL; + curthread->sigbackout = NULL; + done = (seqno != (*cond)->c_seqno); + if (THR_IN_CONDQ(curthread)) { cond_queue_remove(*cond, curthread); /* Check for no more waiters: */ if (TAILQ_FIRST(&(*cond)->c_queue) == NULL) (*cond)->c_mutex = NULL; - - THR_LOCK_RELEASE(curthread, - &(*cond)->c_lock); - } - - /* - * Save the interrupted flag; locking - * the mutex may 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. - */ - if (done || interrupted) { - rval = _mutex_cv_lock(mutex); - unlock_mutex = 1; } } } @@ -341,18 +330,21 @@ _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) /* Trap invalid condition variable types: */ default: - /* Unlock the condition variable structure: */ - THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); - /* Return an invalid argument error: */ rval = EINVAL; break; } - if ((interrupted != 0) && (curthread->continuation != NULL)) - curthread->continuation((void *) curthread); + check_continuation(curthread, *cond, + mutex_locked ? NULL : mutex); } while ((done == 0) && (rval == 0)); + /* Unlock the condition variable structure: */ + THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); + + if (mutex_locked == 0) + _mutex_cv_lock(mutex); + /* Return the completion status: */ return (rval); } @@ -378,8 +370,7 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, struct pthread *curthread = _get_curthread(); int rval = 0; int done = 0; - int interrupted = 0; - int unlock_mutex = 1; + int mutex_locked = 1; int seqno; THR_ASSERT(curthread->locklevel == 0, @@ -407,10 +398,11 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, * and backed out of the waiting queue prior to executing the * signal handler. */ - do { - /* Lock the condition variable structure: */ - THR_LOCK_ACQUIRE(curthread, &(*cond)->c_lock); + /* Lock the condition variable structure: */ + THR_LOCK_ACQUIRE(curthread, &(*cond)->c_lock); + seqno = (*cond)->c_seqno; + do { /* * If the condvar was statically allocated, properly * initialize the tail queue. @@ -428,9 +420,6 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, ((*cond)->c_mutex != *mutex))) { /* Return invalid argument error: */ rval = EINVAL; - - /* Unlock the condition variable structure: */ - THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); } else { /* Set the wakeup time: */ curthread->wakeup_time.tv_sec = abstime->tv_sec; @@ -447,12 +436,8 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, */ cond_queue_enq(*cond, curthread); - /* Remember the mutex and sequence number: */ - (*cond)->c_mutex = *mutex; - seqno = (*cond)->c_seqno; - /* Unlock the mutex: */ - if ((unlock_mutex != 0) && + if (mutex_locked && ((rval = _mutex_cv_unlock(mutex)) != 0)) { /* * Cannot unlock the mutex; remove the @@ -460,21 +445,17 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, * variable queue: */ cond_queue_remove(*cond, curthread); - - /* Check for no more waiters: */ - if (TAILQ_FIRST(&(*cond)->c_queue) == NULL) - (*cond)->c_mutex = NULL; - - /* Unlock the condition variable structure: */ - THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); } else { + /* Remember the mutex: */ + (*cond)->c_mutex = *mutex; + /* * Don't unlock the mutex the next * time through the loop (if the * thread has to be requeued after * handling a signal). */ - unlock_mutex = 0; + mutex_locked = 0; /* * This thread is active and is in a @@ -487,6 +468,7 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, /* Remember the CV: */ curthread->data.cond = *cond; + curthread->sigbackout = cond_wait_backout; THR_SCHED_UNLOCK(curthread, curthread); /* Unlock the CV structure: */ @@ -496,8 +478,6 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, /* Schedule the next thread: */ _thr_sched_switch(curthread); - curthread->data.cond = NULL; - /* * XXX - This really isn't a good check * since there can be more than one @@ -509,38 +489,45 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, * should be sent "as soon as possible". */ done = (seqno != (*cond)->c_seqno); - - if (THR_IN_CONDQ(curthread)) { + if (done && !THR_IN_CONDQ(curthread)) { /* - * Lock the condition variable - * while removing the thread. + * The thread is dequeued, so + * it is safe to clear these. */ - THR_LOCK_ACQUIRE(curthread, - &(*cond)->c_lock); + curthread->data.cond = NULL; + curthread->sigbackout = NULL; + check_continuation(curthread, + NULL, mutex); + return (_mutex_cv_lock(mutex)); + } + /* Relock the CV structure: */ + THR_LOCK_ACQUIRE(curthread, + &(*cond)->c_lock); + + /* + * Clear these after taking the lock to + * prevent a race condition where a + * signal can arrive before dequeueing + * the thread. + */ + curthread->data.cond = NULL; + curthread->sigbackout = NULL; + + done = (seqno != (*cond)->c_seqno); + + if (THR_IN_CONDQ(curthread)) { cond_queue_remove(*cond, curthread); /* Check for no more waiters: */ if (TAILQ_FIRST(&(*cond)->c_queue) == NULL) (*cond)->c_mutex = NULL; - - THR_LOCK_RELEASE(curthread, - &(*cond)->c_lock); } - /* - * Save the interrupted flag; locking - * the mutex may destroy it. - */ - interrupted = curthread->interrupted; if (curthread->timeout != 0) { /* The wait timedout. */ rval = ETIMEDOUT; - (void)_mutex_cv_lock(mutex); - } else if (interrupted || done) { - rval = _mutex_cv_lock(mutex); - unlock_mutex = 1; } } } @@ -548,18 +535,21 @@ _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex, /* Trap invalid condition variable types: */ default: - /* Unlock the condition variable structure: */ - THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); - /* Return an invalid argument error: */ rval = EINVAL; break; } - if ((interrupted != 0) && (curthread->continuation != NULL)) - curthread->continuation((void *)curthread); + check_continuation(curthread, *cond, + mutex_locked ? NULL : mutex); } while ((done == 0) && (rval == 0)); + /* Unlock the condition variable structure: */ + THR_LOCK_RELEASE(curthread, &(*cond)->c_lock); + + if (mutex_locked == 0) + _mutex_cv_lock(mutex); + /* Return the completion status: */ return (rval); } @@ -615,6 +605,7 @@ _pthread_cond_signal(pthread_cond_t * cond) != NULL) { THR_SCHED_LOCK(curthread, pthread); cond_queue_remove(*cond, pthread); + pthread->sigbackout = NULL; if ((pthread->kseg == curthread->kseg) && (pthread->active_priority > curthread->active_priority)) @@ -681,6 +672,7 @@ _pthread_cond_broadcast(pthread_cond_t * cond) != NULL) { THR_SCHED_LOCK(curthread, pthread); cond_queue_remove(*cond, pthread); + pthread->sigbackout = NULL; if ((pthread->kseg == curthread->kseg) && (pthread->active_priority > curthread->active_priority)) @@ -712,9 +704,31 @@ _pthread_cond_broadcast(pthread_cond_t * cond) __strong_reference(_pthread_cond_broadcast, _thr_cond_broadcast); -void -_cond_wait_backout(struct pthread *curthread) +static inline void +check_continuation(struct pthread *curthread, struct pthread_cond *cond, + pthread_mutex_t *mutex) +{ + if ((curthread->interrupted != 0) && + (curthread->continuation != NULL)) { + if (cond != NULL) + /* Unlock the condition variable structure: */ + THR_LOCK_RELEASE(curthread, &cond->c_lock); + /* + * Note that even though this thread may have been + * canceled, POSIX requires that the mutex be + * reaquired prior to cancellation. + */ + if (mutex != NULL) + _mutex_cv_lock(mutex); + curthread->continuation((void *) curthread); + PANIC("continuation returned in pthread_cond_wait.\n"); + } +} + +static void +cond_wait_backout(void *arg) { + struct pthread *curthread = (struct pthread *)arg; pthread_cond_t cond; cond = curthread->data.cond; @@ -740,6 +754,8 @@ _cond_wait_backout(struct pthread *curthread) /* Unlock the condition variable structure: */ THR_LOCK_RELEASE(curthread, &cond->c_lock); } + /* No need to call this again. */ + curthread->sigbackout = NULL; } /* |
