linux-master/ipc/sem.c

129 /* One queue for each sleeping process in the system. */
131 	struct list_head	list;	 /* queue of pending operations */
223  * 2) queue.status: (SEM_BARRIER_2)
305  * merge_queues - merge single semop queues into global queue
308  * This function merges all per-semaphore queues into the global queue.
810  * update_queue is O(N^2) when it restarts scanning the whole queue of
833 	 *   in the queue, then they have observed the original
844  * @wake_q: lockless wake-queue head.
871 		/* operation completed, remove from queue & wakeup */
887  * @wake_q: lockless wake-queue head
889  * Checks all required queue for wait-for-zero operations, based
924 	 * then check the global queue, too.
937  * @wake_q: lockless wake-queue head.
968 		 * be in the  per semaphore pending queue, and decrements
1021  * @wake_q: lockless wake-queue head
1037 		/* semaphore array uses the global queue - just process it. */
1993 	struct sem_queue queue;
2094 	queue.sops = sops;
2095 	queue.nsops = nsops;
2096 	queue.undo = un;
2097 	queue.pid = task_tgid(current);
2098 	queue.alter = alter;
2099 	queue.dupsop = dupsop;
2101 	error = perform_atomic_semop(sma, &queue);
2125 	 * task into the pending queue and go to sleep.
2134 				list_add_tail(&queue.list,
2138 				list_add_tail(&queue.list,
2142 			list_add_tail(&queue.list, &curr->pending_const);
2149 			list_add_tail(&queue.list, &sma->pending_alter);
2151 			list_add_tail(&queue.list, &sma->pending_const);
2158 		WRITE_ONCE(queue.status, -EINTR);
2159 		queue.sleeper = current;
2175 		 * spuriously.  The queue.status is checked again in the
2181 		error = READ_ONCE(queue.status);
2197 		error = READ_ONCE(queue.status);
2200 		 * If queue.status != -EINTR we are woken up by another process.
2207 		 * If an interrupt occurred we have to clean up the queue.
2213 	unlink_queue(sma, &queue);
2330  * should we queue up and wait until we can do so legally?
2331  * The original implementation attempted to do this (queue and wait).