void __wait(volatile int *addr, volatile int *waiters, int val, int priv)
{
int spins=10000;
if (priv) priv = 128; priv=0;
while (spins--) {
if (*addr==val) a_spin();
else return;
}
if (waiters) a_inc(waiters);
while (*addr==val) {
#ifdef __EMSCRIPTEN__
if (pthread_self()->cancelasync == PTHREAD_CANCEL_ASYNCHRONOUS) {
// Must wait in slices in case this thread is cancelled in between.
int e;
do {
if (_pthread_isduecanceled(pthread_self())) {
if (waiters) a_dec(waiters);
return;
}
e = emscripten_futex_wait((void*)addr, val, 100);
} while(e == -ETIMEDOUT);
} else {
// Can wait in one go.
emscripten_futex_wait((void*)addr, val, INFINITY);
}
#else
__syscall(SYS_futex, addr, FUTEX_WAIT|priv, val, 0);
#endif
}
if (waiters) a_dec(waiters);
}
void __lock(volatile int *l)
{
int spins=100000;
/* Do not use futexes because we insist that unlocking is a simple
* assignment to optimize non-pathological code with no contention. */
while (a_xchg(l, 1))
if (spins) spins--, a_spin();
else __syscall(SYS_sched_yield);
}
void __wait(volatile int *addr, volatile int *waiters, int val, int priv)
{
int spins=50000;
if (priv) priv = 128; priv=0;
while (spins--) {
if (*addr==val) a_spin();
else return;
}
if (waiters) a_inc(waiters);
while (*addr==val)
__syscall(SYS_futex, (long)addr, FUTEX_WAIT|priv, val, 0);
if (waiters) a_dec(waiters);
}
int pthread_barrier_wait(pthread_barrier_t *b)
{
int limit = b->_b_limit;
struct instance *inst;
/* Trivial case: count was set at 1 */
if (!limit) return PTHREAD_BARRIER_SERIAL_THREAD;
/* Process-shared barriers require a separate, inefficient wait */
if (limit < 0) return pshared_barrier_wait(b);
/* Otherwise we need a lock on the barrier object */
while (a_swap(&b->_b_lock, 1))
__wait(&b->_b_lock, &b->_b_waiters, 1, 1);
inst = b->_b_inst;
/* First thread to enter the barrier becomes the "instance owner" */
if (!inst) {
struct instance new_inst = { 0 };
int spins = 10000;
b->_b_inst = inst = &new_inst;
a_store(&b->_b_lock, 0);
if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
while (spins-- && !inst->finished)
a_spin();
a_inc(&inst->finished);
while (inst->finished == 1)
__syscall(SYS_futex, &inst->finished, FUTEX_WAIT,1,0);
return PTHREAD_BARRIER_SERIAL_THREAD;
}
/* Last thread to enter the barrier wakes all non-instance-owners */
if (++inst->count == limit) {
b->_b_inst = 0;
a_store(&b->_b_lock, 0);
if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
a_store(&inst->last, 1);
if (inst->waiters)
__wake(&inst->last, -1, 1);
} else {
a_store(&b->_b_lock, 0);
if (b->_b_waiters) __wake(&b->_b_lock, 1, 1);
__wait(&inst->last, &inst->waiters, 0, 1);
}
/* Last thread to exit the barrier wakes the instance owner */
if (a_fetch_add(&inst->count,-1)==1 && a_fetch_add(&inst->finished,1))
__wake(&inst->finished, 1, 1);
return 0;
}
int pthread_spin_lock(pthread_spinlock_t *s)
{
while (a_swap(s, 1)) a_spin();
return 0;
}
