Function selrecord

freebsd/kern/sys_generic.c:1786–1831

* Record a select request. */

 * Record a select request.
 */
void
selrecord(struct thread *selector, struct selinfo *sip)
{
	struct selfd *sfp;
	struct seltd *stp;
	struct mtx *mtxp;

	stp = selector->td_sel;
	/*
	 * Don't record when doing a rescan.
	 */
	if (stp->st_flags & SELTD_RESCAN)
		return;
	/*
	 * Grab one of the preallocated descriptors.
	 */
	sfp = NULL;
	if ((sfp = stp->st_free1) != NULL)
		stp->st_free1 = NULL;
	else if ((sfp = stp->st_free2) != NULL)
		stp->st_free2 = NULL;
	else
		panic("selrecord: No free selfd on selq");
	mtxp = sip->si_mtx;
	if (mtxp == NULL)
		mtxp = mtx_pool_find(mtxpool_select, sip);
	/*
	 * Initialize the sfp and queue it in the thread.
	 */
	sfp->sf_si = sip;
	sfp->sf_mtx = mtxp;
	STAILQ_INSERT_TAIL(&stp->st_selq, sfp, sf_link);
	/*
	 * Now that we've locked the sip, check for initialization.
	 */
	mtx_lock(mtxp);
	if (sip->si_mtx == NULL) {
		sip->si_mtx = mtxp;
		TAILQ_INIT(&sip->si_tdlist);
	}
	/*
	 * Add this thread to the list of selfds listening on this selinfo.
	 */
	TAILQ_INSERT_TAIL(&sip->si_tdlist, sfp, sf_threads);
	mtx_unlock(sip->si_mtx);
}

/* Wake up a selecting thread. */
void