Function vm_page_sunbusy

freebsd/vm/vm_page.c:975–1001

* vm_page_sunbusy: * * Shared unbusy a page. */

 *	Shared unbusy a page.
 */
void
vm_page_sunbusy(vm_page_t m)
{
	u_int x;

	vm_page_assert_sbusied(m);

	x = vm_page_busy_fetch(m);
	for (;;) {
		KASSERT(x != VPB_FREED,
		    ("vm_page_sunbusy: Unlocking freed page."));
		if (VPB_SHARERS(x) > 1) {
			if (atomic_fcmpset_int(&m->busy_lock, &x,
			    x - VPB_ONE_SHARER))
				break;
			continue;
		}
		KASSERT((x & ~VPB_BIT_WAITERS) == VPB_SHARERS_WORD(1),
		    ("vm_page_sunbusy: invalid lock state"));
		if (!atomic_fcmpset_rel_int(&m->busy_lock, &x, VPB_UNBUSIED))
			continue;
		if ((x & VPB_BIT_WAITERS) == 0)
			break;
		wakeup(m);
		break;
	}
}

/*
 *	vm_page_busy_sleep: