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
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 */
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;
__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);
__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) {
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