diff options
Diffstat (limited to 'src/thread/pthread_cond_timedwait.c')
| -rw-r--r-- | src/thread/pthread_cond_timedwait.c | 149 |
1 files changed, 63 insertions, 86 deletions
diff --git a/src/thread/pthread_cond_timedwait.c b/src/thread/pthread_cond_timedwait.c index 5f29a249..d28b478e 100644 --- a/src/thread/pthread_cond_timedwait.c +++ b/src/thread/pthread_cond_timedwait.c @@ -3,6 +3,7 @@ void __pthread_testcancel(void); int __pthread_mutex_lock(pthread_mutex_t *); int __pthread_mutex_unlock(pthread_mutex_t *); +int __pthread_setcancelstate(int, int *); /* * struct waiter @@ -28,11 +29,8 @@ int __pthread_mutex_unlock(pthread_mutex_t *); struct waiter { struct waiter *prev, *next; - int state, barrier, mutex_ret; + int state, barrier; int *notify; - pthread_mutex_t *mutex; - pthread_cond_t *cond; - int shared, err; }; /* Self-synchronized-destruction-safe lock functions */ @@ -66,83 +64,14 @@ enum { LEAVING, }; -static void unwait(void *arg) -{ - struct waiter *node = arg; - - if (node->shared) { - pthread_cond_t *c = node->cond; - pthread_mutex_t *m = node->mutex; - /* Suppress cancellation if a signal was potentially - * consumed; this is a legitimate form of spurious - * wake even if not. */ - if (node->err == ECANCELED && c->_c_seq != node->state) - node->err = 0; - if (a_fetch_add(&c->_c_waiters, -1) == -0x7fffffff) - __wake(&c->_c_waiters, 1, 0); - node->mutex_ret = pthread_mutex_lock(m); - return; - } - - int oldstate = a_cas(&node->state, WAITING, LEAVING); - - if (oldstate == WAITING) { - /* Access to cv object is valid because this waiter was not - * yet signaled and a new signal/broadcast cannot return - * after seeing a LEAVING waiter without getting notified - * via the futex notify below. */ - - pthread_cond_t *c = node->cond; - lock(&c->_c_lock); - - if (c->_c_head == node) c->_c_head = node->next; - else if (node->prev) node->prev->next = node->next; - if (c->_c_tail == node) c->_c_tail = node->prev; - else if (node->next) node->next->prev = node->prev; - - unlock(&c->_c_lock); - - if (node->notify) { - if (a_fetch_add(node->notify, -1)==1) - __wake(node->notify, 1, 1); - } - } else { - /* Lock barrier first to control wake order. */ - lock(&node->barrier); - } - - node->mutex_ret = pthread_mutex_lock(node->mutex); - - if (oldstate == WAITING) return; - - if (!node->next) a_inc(&node->mutex->_m_waiters); - - /* Unlock the barrier that's holding back the next waiter, and - * either wake it or requeue it to the mutex. */ - if (node->prev) { - unlock_requeue(&node->prev->barrier, - &node->mutex->_m_lock, - node->mutex->_m_type & 128); - } else { - a_dec(&node->mutex->_m_waiters); - } - - /* Since a signal was consumed, acting on cancellation is not - * permitted. The only other error possible at this stage, - * ETIMEDOUT, is permitted even if a signal was consumed. */ - if (node->err = ECANCELED) node->err = 0; -} - static void dummy(void *arg) { } -int __pthread_setcancelstate(int, int *); - int __pthread_cond_timedwait(pthread_cond_t *restrict c, pthread_mutex_t *restrict m, const struct timespec *restrict ts) { - struct waiter node = { .cond = c, .mutex = m }; - int e, seq, *fut, clock = c->_c_clock, cs; + struct waiter node = { 0 }; + int e, seq, *fut, clock = c->_c_clock, cs, shared=0, oldstate, tmp; if ((m->_m_type&15) && (m->_m_lock&INT_MAX) != __pthread_self()->tid) return EPERM; @@ -153,9 +82,9 @@ int __pthread_cond_timedwait(pthread_cond_t *restrict c, pthread_mutex_t *restri __pthread_testcancel(); if (c->_c_shared) { - node.shared = 1; + shared = 1; fut = &c->_c_seq; - seq = node.state = c->_c_seq; + seq = c->_c_seq; a_inc(&c->_c_waiters); } else { lock(&c->_c_lock); @@ -175,20 +104,68 @@ int __pthread_cond_timedwait(pthread_cond_t *restrict c, pthread_mutex_t *restri __pthread_setcancelstate(PTHREAD_CANCEL_MASKED, &cs); - do e = __timedwait(fut, seq, clock, ts, dummy, 0, !node.shared); + do e = __timedwait(fut, seq, clock, ts, dummy, 0, !shared); while (*fut==seq && (!e || e==EINTR)); if (e == EINTR) e = 0; - node.err = e; - unwait(&node); - e = node.err; + if (shared) { + /* Suppress cancellation if a signal was potentially + * consumed; this is a legitimate form of spurious + * wake even if not. */ + if (e == ECANCELED && c->_c_seq != seq) e = 0; + if (a_fetch_add(&c->_c_waiters, -1) == -0x7fffffff) + __wake(&c->_c_waiters, 1, 0); + oldstate = WAITING; + goto relock; + } + + oldstate = a_cas(&node.state, WAITING, LEAVING); + + if (oldstate == WAITING) { + /* Access to cv object is valid because this waiter was not + * yet signaled and a new signal/broadcast cannot return + * after seeing a LEAVING waiter without getting notified + * via the futex notify below. */ + + lock(&c->_c_lock); + + if (c->_c_head == &node) c->_c_head = node.next; + else if (node.prev) node.prev->next = node.next; + if (c->_c_tail == &node) c->_c_tail = node.prev; + else if (node.next) node.next->prev = node.prev; + + unlock(&c->_c_lock); + + if (node.notify) { + if (a_fetch_add(node.notify, -1)==1) + __wake(node.notify, 1, 1); + } + } else { + /* Lock barrier first to control wake order. */ + lock(&node.barrier); + } + +relock: + /* Errors locking the mutex override any existing error or + * cancellation, since the caller must see them to know the + * state of the mutex. */ + if ((tmp = pthread_mutex_lock(m))) e = tmp; + + if (oldstate == WAITING) goto done; + + if (!node.next) a_inc(&m->_m_waiters); + + /* Unlock the barrier that's holding back the next waiter, and + * either wake it or requeue it to the mutex. */ + if (node.prev) + unlock_requeue(&node.prev->barrier, &m->_m_lock, m->_m_type & 128); + else + a_dec(&m->_m_waiters); - /* Suppress cancellation if there was an error locking the mutex, - * since the contract for cancellation requires the mutex to be - * locked when the cleanup handler is called, and there is no - * way to report an error. */ - if (node.mutex_ret) e = node.mutex_ret; + /* Since a signal was consumed, cancellation is not permitted. */ + if (e = ECANCELED) e = 0; +done: __pthread_setcancelstate(cs, 0); if (e == ECANCELED) { |