Function uifind

freebsd/kern/kern_resource.c:1368–1412

* Find or allocate a struct uidinfo for a particular uid. * Returns with uidinfo struct referenced. * uifree() should be called on a struct uidinfo when released. */

 * uifree() should be called on a struct uidinfo when released.
 */
struct uidinfo *
uifind(uid_t uid)
{
	struct uidinfo *new_uip, *uip;
	struct ucred *cred;

	cred = curthread->td_ucred;
	if (cred->cr_uidinfo->ui_uid == uid) {
		uip = cred->cr_uidinfo;
		uihold(uip);
		return (uip);
	} else if (cred->cr_ruidinfo->ui_uid == uid) {
		uip = cred->cr_ruidinfo;
		uihold(uip);
		return (uip);
	}

	rw_rlock(&uihashtbl_lock);
	uip = uilookup(uid);
	rw_runlock(&uihashtbl_lock);
	if (uip != NULL)
		return (uip);

	new_uip = malloc(sizeof(*new_uip), M_UIDINFO, M_WAITOK | M_ZERO);
	racct_create(&new_uip->ui_racct);
	refcount_init(&new_uip->ui_ref, 1);
	new_uip->ui_uid = uid;

	rw_wlock(&uihashtbl_lock);
	/*
	 * There's a chance someone created our uidinfo while we
	 * were in malloc and not holding the lock, so we have to
	 * make sure we don't insert a duplicate uidinfo.
	 */
	if ((uip = uilookup(uid)) == NULL) {
		LIST_INSERT_HEAD(UIHASH(uid), new_uip, ui_hash);
		rw_wunlock(&uihashtbl_lock);
		uip = new_uip;
	} else {
		rw_wunlock(&uihashtbl_lock);
		racct_destroy(&new_uip->ui_racct);
		free(new_uip, M_UIDINFO);
	}
	return (uip);
}

/*
 * Place another refcount on a uidinfo struct.