Function sleepq_catch_signals

freebsd/kern/subr_sleepqueue.c:502–539

* Marks the pending sleep of the current thread as interruptible and * makes an initial check for pending signals before putting a thread * to sleep. Enters and exits with the thread lock held. Thread lock * may have transitioned from the sleepq lock to a run lock. */

 * may have transitioned from the sleepq lock to a run lock.
 */
static int
sleepq_catch_signals(const void *wchan, int pri)
{
	struct thread *td;
	struct sleepqueue_chain *sc;
	struct sleepqueue *sq;
	int ret;

	sc = SC_LOOKUP(wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	MPASS(wchan != NULL);
	td = curthread;

	ret = sleepq_check_ast_sc_locked(td, sc);
	THREAD_LOCK_ASSERT(td, MA_OWNED);
	mtx_assert(&sc->sc_lock, MA_OWNED);

	if (ret == 0) {
		/*
		 * No pending signals and no suspension requests found.
		 * Switch the thread off the cpu.
		 */
		sleepq_switch(wchan, pri);
	} else {
		/*
		 * There were pending signals and this thread is still
		 * on the sleep queue, remove it from the sleep queue.
		 */
		if (TD_ON_SLEEPQ(td)) {
			sq = sleepq_lookup(wchan);
			sleepq_remove_thread(sq, td);
		}
		MPASS(td->td_lock != &sc->sc_lock);
		mtx_unlock_spin(&sc->sc_lock);
		thread_unlock(td);
	}
	return (ret);
}

/*
 * Switches to another thread if we are still asleep on a sleep queue.