common/syscall/sem.c

72  * Removing the undo structure tunables involved a serious redesign of
73  * how they were implemented.  There is now one undo structure for
76  * to.  To avoid scalability and performance problems, the undo
83  * The latter is used when removing the semaphore, so the undo
86  * The undo structure itself contains pointers to the ksemid and proc
88  * adjust-on-exit (AOE) values.  When an undo structure is allocated it
97  * sem_rmid, holding the ID lock, iterates through all undo structures
99  * see if p_semacct is NULL.  If it is, it skips that undo structure
100  * and continues to the next.  Otherwise, it removes the undo structure
102  * hold that the undo structure had on the semaphore.
107  * up all undo structures found in the tree -- a coexecuting sem_rmid
108  * will see the NULL p_semacct and skip that undo structure.  It walks
109  * the AVL tree (using avl_destroy_nodes) and for each undo structure
111  * undo structure has a hold on the semaphore), updates all semaphores
114  * semaphore, drops the ID lock, and frees the undo structure.
253 sem_undo_add(short val, ushort_t num, struct sem_undo *undo)
255 	int newval = undo->un_aoe[num] - val;
259 	undo->un_aoe[num] = newval;
265  * sem_undo_clear - clears all undo entries for specified semaphores
272 	struct sem_undo *undo;
278 	for (undo = list_head(&sp->sem_undos); undo;
279 	    undo = list_next(&sp->sem_undos, undo))
281 			undo->un_aoe[i] = 0;
288 sem_rollback(ksemid_t *sp, struct sembuf *op, int n, struct sem_undo *undo)
298 			ASSERT(undo != NULL);
299 			(void) sem_undo_add(-op->sem_op, op->sem_num, undo);
309 	struct sem_undo *undo;
314 	while (undo = list_head(&sp->sem_undos)) {
315 		list_remove(&sp->sem_undos, undo);
316 		mutex_enter(&undo->un_proc->p_lock);
317 		if (undo->un_proc->p_semacct == NULL) {
318 			mutex_exit(&undo->un_proc->p_lock);
321 		avl_remove(undo->un_proc->p_semacct, undo);
322 		mutex_exit(&undo->un_proc->p_lock);
323 		kmem_free(undo, size);
610 	struct sem_undo	*undo;
618 	while (undo = avl_destroy_nodes(tree, &cookie)) {
619 		ksemid_t *sp = undo->un_sp;
626 				int adj = undo->un_aoe[i];
640 			list_remove(&sp->sem_undos, undo);
643 		kmem_free(undo, size);
802  * Helper function for semop - creates an undo structure and adds it to
810 	struct sem_undo *undo;
817 	undo = kmem_zalloc(size, KM_SLEEP);
818 	undo->un_proc = pp;
819 	undo->un_sp = sp;
826 		kmem_free(undo, size);
846 		kmem_free(undo, size);
848 		*un = undo;
849 		avl_insert(pp->p_semacct, undo, where);
851 		list_insert_head(&sp->sem_undos, undo);
876 	struct sem_undo	*undo;
972 	 * operations are marked SEM_UNDO, find (or allocate) the undo
995 			undo = avl_find(pp->p_semacct, &template, NULL);
997 			undo = NULL;
999 		if (undo == NULL) {
1005 			    &undo))
1017 	 * Actually, do the operations and undo them if a wait is needed
1031 			    undo)))) {
1033 					sem_rollback(sp, uops, i, undo);
1061 				    op->sem_num, undo))) {
1063 						sem_rollback(sp, uops, i, undo);
1072 				sem_rollback(sp, uops, i, undo);
1119 				sem_rollback(sp, uops, i, undo);