void* wsd_work_stealing_deque_steal(wsd_work_stealing_deque_t* d)
{
assert(d);
const int64_t t = d->top;
load_load_barrier();
const int64_t b = d->bottom;
wsd_circular_array_t* const a = d->underlying_array;
const int64_t size = b - t;
if(size <= 0) {
return WSD_EMPTY;
}
void* const ret = wsd_circular_array_get(a, t);
if(!__sync_bool_compare_and_swap(&d->top, t, t + 1)) {
return WSD_ABORT;
}
return ret;
}
size_t fiber_poll_events_blocking(uint32_t seconds, uint32_t useconds)
{
if(!fiber_loop) {
fiber_do_real_sleep(seconds, useconds);
return 0;
}
load_load_barrier();//needed to ensure we read fiber_loop first - we need a valid active_thread count,
//so init writes active_threads then fiber_loop, we read here in the reverse order
//only allow the final thread to perform a blocking poll - this prevents the
//thread from locking out other threads trying to register for events
const int local_count = __sync_sub_and_fetch(&active_threads, 1);
assert(local_count >= 0);
if(local_count > 0) {
fiber_do_real_sleep(seconds, useconds);
__sync_add_and_fetch(&active_threads, 1);
return 0;
}
fiber_spinlock_lock(&fiber_loop_spinlock);
if(!fiber_loop) {
__sync_add_and_fetch(&active_threads, 1);
fiber_spinlock_unlock(&fiber_loop_spinlock);
return 0;
}
num_events_triggered = 0;
fiber_manager_get()->poll_count += 1;
ev_run(fiber_loop, EVRUN_ONCE);
const int local_copy = num_events_triggered;
fiber_spinlock_unlock(&fiber_loop_spinlock);
__sync_add_and_fetch(&active_threads, 1);
return local_copy;
}
