#include "pthread_impl.h"
#include <threads.h>

int cnd_signal(cnd_t * cond) {
	int ret = thrd_success;

	/* Avoid fight for critical section if there is nothing to
	   do. */
	if (!cond || !cond->_cx_cnd) return ret;

	/* Critical section protected by lock */
	__lock(&cond->_cx_lock);
	__cnd_t * c = cond->_cx_cnd;
	if (c) {
		if (c->wts) {
			++c->seq;
			/* Move one waiter to the ones to be woken up, later. */
			--c->wts;
			/* If this was the last waiter, unlink. */
			if (!c->wts) cond->_cx_cnd = 0;
			else __cnd_addref(c);
		} else {
			c = 0;
		}
	}
	__unlock(&cond->_cx_lock);

	/* If c is 0, there haven't been any waiters, yet, nothing to do. */
	if (c) {
		/* Do the delayed work. */
		a_inc(&c->tok);
		/* Move the threads of the previous sequence point to the token queue. */
		int ret0 = __syscall(SYS_futex, &c->seq, FUTEX_REQUEUE|THRD_PRIVATE,
		                     0,
		                     INT_MAX, &c->tok);
		int ret1 = __syscall(SYS_futex, &c->tok, FUTEX_WAKE|THRD_PRIVATE, 1);
		ret = ((ret0 < 0) || (ret1 < 0)) ? thrd_error : thrd_success;
		__cnd_unref(c);
	}
	return ret;
}