zircon/third_party/ulib/musl/pthread/pthread_rwlock_timedrdlock.c

#include "atomic.h"
#include "threads_impl.h"

int pthread_rwlock_timedrdlock(pthread_rwlock_t* restrict rw, const struct timespec* restrict at) {
  int r, t;

  r = pthread_rwlock_tryrdlock(rw);
  if (r != EBUSY)
    return r;

  int spins = 100;
  while (spins-- && atomic_load(&rw->_rw_lock) && !atomic_load(&rw->_rw_waiters))
    a_spin();

  while ((r = pthread_rwlock_tryrdlock(rw)) == EBUSY) {
    if (!(r = atomic_load(&rw->_rw_lock)) ||
        ((r & PTHREAD_MUTEX_RWLOCK_COUNT_MASK) != PTHREAD_MUTEX_RWLOCK_LOCKED_FOR_WR)) {
      continue;
    }

    t = r | PTHREAD_MUTEX_RWLOCK_CONTESTED_BIT;
    atomic_fetch_add(&rw->_rw_waiters, 1);
    a_cas_shim(&rw->_rw_lock, r, t);
    r = __timedwait(&rw->_rw_lock, t, CLOCK_REALTIME, at);
    atomic_fetch_sub(&rw->_rw_waiters, 1);
    if (r)
      return r;
  }
  return r;
}