Function lf_activate_lock

freebsd/kern/kern_lockf.c:1213–1320

* Add a lock to the active list, updating or removing any current * locks owned by the same owner and processing any pending locks that * become unblocked as a result. This code is also used for unlock * since the logic for updating existing locks is identical. * * As a result of processing the new lock, we may unblock existing * pending locks as a result of downgrading/unlocking. We simply

 * not a real problem.
 */
static void
lf_activate_lock(struct lockf *state, struct lockf_entry *lock)
{
	struct lockf_entry *overlap, *lf;
	struct lockf_entry_list granted;
	int ovcase;

	LIST_INIT(&granted);
	LIST_INSERT_HEAD(&granted, lock, lf_link);

	while (!LIST_EMPTY(&granted)) {
		lock = LIST_FIRST(&granted);
		LIST_REMOVE(lock, lf_link);

		/*
		 * Skip over locks owned by other processes.  Handle
		 * any locks that overlap and are owned by ourselves.
		 */
		overlap = LIST_FIRST(&state->ls_active);
		for (;;) {
			ovcase = lf_findoverlap(&overlap, lock, SELF);

#ifdef LOCKF_DEBUG
			if (ovcase && (lockf_debug & 2)) {
				printf("lf_setlock: overlap %d", ovcase);
				lf_print("", overlap);
			}
#endif
			/*
			 * Six cases:
			 *	0) no overlap
			 *	1) overlap == lock
			 *	2) overlap contains lock
			 *	3) lock contains overlap
			 *	4) overlap starts before lock
			 *	5) overlap ends after lock
			 */
			switch (ovcase) {
			case 0: /* no overlap */
				break;

			case 1: /* overlap == lock */
				/*
				 * We have already setup the
				 * dependants for the new lock, taking
				 * into account a possible downgrade
				 * or unlock. Remove the old lock.
				 */
				LIST_REMOVE(overlap, lf_link);
				lf_update_dependancies(state, overlap, TRUE,
					&granted);
				lf_free_lock(overlap);
				break;

			case 2: /* overlap contains lock */
				/*
				 * Just split the existing lock.
				 */