fusl/src/thread/pthread_rwlock_tryrdlock.c

#include "pthread_impl.h"

int pthread_rwlock_tryrdlock(pthread_rwlock_t* rw) {
  int val, cnt;
  do {
    val = rw->_rw_lock;
    cnt = val & 0x7fffffff;
    if (cnt == 0x7fffffff)
      return EBUSY;
    if (cnt == 0x7ffffffe)
      return EAGAIN;
  } while (a_cas(&rw->_rw_lock, val, val + 1) != val);
  return 0;
}