third_party/ulib/musl/pthread/pthread_rwlock_unlock.c

#include "futex_impl.h"
#include "threads_impl.h"

int pthread_rwlock_unlock(pthread_rwlock_t* rw) {
    int val, cnt, waiters, new;

    do {
        val = atomic_load(&rw->_rw_lock);
        cnt = val & 0x7fffffff;
        waiters = atomic_load(&rw->_rw_waiters);
        new = (cnt == 0x7fffffff || cnt == 1) ? 0 : val - 1;
    } while (a_cas_shim(&rw->_rw_lock, val, new) != val);

    if (!new && (waiters || val < 0))
        _zx_futex_wake(&rw->_rw_lock, cnt);

    return 0;
}