sem.c revision 9b44ee2e
1/*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
6 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
7 *
8 * SMP-threaded, sysctl's added
9 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
10 * Enforced range limit on SEM_UNDO
11 * (c) 2001 Red Hat Inc
12 * Lockless wakeup
13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
14 * Further wakeup optimizations, documentation
15 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
16 *
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
19 *
20 * namespaces support
21 * OpenVZ, SWsoft Inc.
22 * Pavel Emelianov <xemul@openvz.org>
23 *
24 * Implementation notes: (May 2010)
25 * This file implements System V semaphores.
26 *
27 * User space visible behavior:
28 * - FIFO ordering for semop() operations (just FIFO, not starvation
29 *   protection)
30 * - multiple semaphore operations that alter the same semaphore in
31 *   one semop() are handled.
32 * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
33 *   SETALL calls.
34 * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
35 * - undo adjustments at process exit are limited to 0..SEMVMX.
36 * - namespace are supported.
37 * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
38 *   to /proc/sys/kernel/sem.
39 * - statistics about the usage are reported in /proc/sysvipc/sem.
40 *
41 * Internals:
42 * - scalability:
43 *   - all global variables are read-mostly.
44 *   - semop() calls and semctl(RMID) are synchronized by RCU.
45 *   - most operations do write operations (actually: spin_lock calls) to
46 *     the per-semaphore array structure.
47 *   Thus: Perfect SMP scaling between independent semaphore arrays.
48 *         If multiple semaphores in one array are used, then cache line
49 *         trashing on the semaphore array spinlock will limit the scaling.
50 * - semncnt and semzcnt are calculated on demand in count_semcnt()
51 * - the task that performs a successful semop() scans the list of all
52 *   sleeping tasks and completes any pending operations that can be fulfilled.
53 *   Semaphores are actively given to waiting tasks (necessary for FIFO).
54 *   (see update_queue())
55 * - To improve the scalability, the actual wake-up calls are performed after
56 *   dropping all locks. (see wake_up_sem_queue_prepare(),
57 *   wake_up_sem_queue_do())
58 * - All work is done by the waker, the woken up task does not have to do
59 *   anything - not even acquiring a lock or dropping a refcount.
60 * - A woken up task may not even touch the semaphore array anymore, it may
61 *   have been destroyed already by a semctl(RMID).
62 * - The synchronizations between wake-ups due to a timeout/signal and a
63 *   wake-up due to a completed semaphore operation is achieved by using an
64 *   intermediate state (IN_WAKEUP).
65 * - UNDO values are stored in an array (one per process and per
66 *   semaphore array, lazily allocated). For backwards compatibility, multiple
67 *   modes for the UNDO variables are supported (per process, per thread)
68 *   (see copy_semundo, CLONE_SYSVSEM)
69 * - There are two lists of the pending operations: a per-array list
70 *   and per-semaphore list (stored in the array). This allows to achieve FIFO
71 *   ordering without always scanning all pending operations.
72 *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
73 */
74
75#include <linux/slab.h>
76#include <linux/spinlock.h>
77#include <linux/init.h>
78#include <linux/proc_fs.h>
79#include <linux/time.h>
80#include <linux/security.h>
81#include <linux/syscalls.h>
82#include <linux/audit.h>
83#include <linux/capability.h>
84#include <linux/seq_file.h>
85#include <linux/rwsem.h>
86#include <linux/nsproxy.h>
87#include <linux/ipc_namespace.h>
88
89#include <linux/uaccess.h>
90#include "util.h"
91
92/* One semaphore structure for each semaphore in the system. */
93struct sem {
94	int	semval;		/* current value */
95	int	sempid;		/* pid of last operation */
96	spinlock_t	lock;	/* spinlock for fine-grained semtimedop */
97	struct list_head pending_alter; /* pending single-sop operations */
98					/* that alter the semaphore */
99	struct list_head pending_const; /* pending single-sop operations */
100					/* that do not alter the semaphore*/
101	time_t	sem_otime;	/* candidate for sem_otime */
102} ____cacheline_aligned_in_smp;
103
104/* One queue for each sleeping process in the system. */
105struct sem_queue {
106	struct list_head	list;	 /* queue of pending operations */
107	struct task_struct	*sleeper; /* this process */
108	struct sem_undo		*undo;	 /* undo structure */
109	int			pid;	 /* process id of requesting process */
110	int			status;	 /* completion status of operation */
111	struct sembuf		*sops;	 /* array of pending operations */
112	struct sembuf		*blocking; /* the operation that blocked */
113	int			nsops;	 /* number of operations */
114	int			alter;	 /* does *sops alter the array? */
115};
116
117/* Each task has a list of undo requests. They are executed automatically
118 * when the process exits.
119 */
120struct sem_undo {
121	struct list_head	list_proc;	/* per-process list: *
122						 * all undos from one process
123						 * rcu protected */
124	struct rcu_head		rcu;		/* rcu struct for sem_undo */
125	struct sem_undo_list	*ulp;		/* back ptr to sem_undo_list */
126	struct list_head	list_id;	/* per semaphore array list:
127						 * all undos for one array */
128	int			semid;		/* semaphore set identifier */
129	short			*semadj;	/* array of adjustments */
130						/* one per semaphore */
131};
132
133/* sem_undo_list controls shared access to the list of sem_undo structures
134 * that may be shared among all a CLONE_SYSVSEM task group.
135 */
136struct sem_undo_list {
137	atomic_t		refcnt;
138	spinlock_t		lock;
139	struct list_head	list_proc;
140};
141
142
143#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
144
145#define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
146
147static int newary(struct ipc_namespace *, struct ipc_params *);
148static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
149#ifdef CONFIG_PROC_FS
150static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
151#endif
152
153#define SEMMSL_FAST	256 /* 512 bytes on stack */
154#define SEMOPM_FAST	64  /* ~ 372 bytes on stack */
155
156/*
157 * Locking:
158 *	sem_undo.id_next,
159 *	sem_array.complex_count,
160 *	sem_array.pending{_alter,_cont},
161 *	sem_array.sem_undo: global sem_lock() for read/write
162 *	sem_undo.proc_next: only "current" is allowed to read/write that field.
163 *
164 *	sem_array.sem_base[i].pending_{const,alter}:
165 *		global or semaphore sem_lock() for read/write
166 */
167
168#define sc_semmsl	sem_ctls[0]
169#define sc_semmns	sem_ctls[1]
170#define sc_semopm	sem_ctls[2]
171#define sc_semmni	sem_ctls[3]
172
173void sem_init_ns(struct ipc_namespace *ns)
174{
175	ns->sc_semmsl = SEMMSL;
176	ns->sc_semmns = SEMMNS;
177	ns->sc_semopm = SEMOPM;
178	ns->sc_semmni = SEMMNI;
179	ns->used_sems = 0;
180	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
181}
182
183#ifdef CONFIG_IPC_NS
184void sem_exit_ns(struct ipc_namespace *ns)
185{
186	free_ipcs(ns, &sem_ids(ns), freeary);
187	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
188}
189#endif
190
191void __init sem_init(void)
192{
193	sem_init_ns(&init_ipc_ns);
194	ipc_init_proc_interface("sysvipc/sem",
195				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
196				IPC_SEM_IDS, sysvipc_sem_proc_show);
197}
198
199/**
200 * unmerge_queues - unmerge queues, if possible.
201 * @sma: semaphore array
202 *
203 * The function unmerges the wait queues if complex_count is 0.
204 * It must be called prior to dropping the global semaphore array lock.
205 */
206static void unmerge_queues(struct sem_array *sma)
207{
208	struct sem_queue *q, *tq;
209
210	/* complex operations still around? */
211	if (sma->complex_count)
212		return;
213	/*
214	 * We will switch back to simple mode.
215	 * Move all pending operation back into the per-semaphore
216	 * queues.
217	 */
218	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
219		struct sem *curr;
220		curr = &sma->sem_base[q->sops[0].sem_num];
221
222		list_add_tail(&q->list, &curr->pending_alter);
223	}
224	INIT_LIST_HEAD(&sma->pending_alter);
225}
226
227/**
228 * merge_queues - merge single semop queues into global queue
229 * @sma: semaphore array
230 *
231 * This function merges all per-semaphore queues into the global queue.
232 * It is necessary to achieve FIFO ordering for the pending single-sop
233 * operations when a multi-semop operation must sleep.
234 * Only the alter operations must be moved, the const operations can stay.
235 */
236static void merge_queues(struct sem_array *sma)
237{
238	int i;
239	for (i = 0; i < sma->sem_nsems; i++) {
240		struct sem *sem = sma->sem_base + i;
241
242		list_splice_init(&sem->pending_alter, &sma->pending_alter);
243	}
244}
245
246static void sem_rcu_free(struct rcu_head *head)
247{
248	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
249	struct sem_array *sma = ipc_rcu_to_struct(p);
250
251	security_sem_free(sma);
252	ipc_rcu_free(head);
253}
254
255/*
256 * Wait until all currently ongoing simple ops have completed.
257 * Caller must own sem_perm.lock.
258 * New simple ops cannot start, because simple ops first check
259 * that sem_perm.lock is free.
260 * that a) sem_perm.lock is free and b) complex_count is 0.
261 */
262static void sem_wait_array(struct sem_array *sma)
263{
264	int i;
265	struct sem *sem;
266
267	if (sma->complex_count)  {
268		/* The thread that increased sma->complex_count waited on
269		 * all sem->lock locks. Thus we don't need to wait again.
270		 */
271		return;
272	}
273
274	for (i = 0; i < sma->sem_nsems; i++) {
275		sem = sma->sem_base + i;
276		spin_unlock_wait(&sem->lock);
277	}
278}
279
280/*
281 * If the request contains only one semaphore operation, and there are
282 * no complex transactions pending, lock only the semaphore involved.
283 * Otherwise, lock the entire semaphore array, since we either have
284 * multiple semaphores in our own semops, or we need to look at
285 * semaphores from other pending complex operations.
286 */
287static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
288			      int nsops)
289{
290	struct sem *sem;
291
292	if (nsops != 1) {
293		/* Complex operation - acquire a full lock */
294		ipc_lock_object(&sma->sem_perm);
295
296		/* And wait until all simple ops that are processed
297		 * right now have dropped their locks.
298		 */
299		sem_wait_array(sma);
300		return -1;
301	}
302
303	/*
304	 * Only one semaphore affected - try to optimize locking.
305	 * The rules are:
306	 * - optimized locking is possible if no complex operation
307	 *   is either enqueued or processed right now.
308	 * - The test for enqueued complex ops is simple:
309	 *      sma->complex_count != 0
310	 * - Testing for complex ops that are processed right now is
311	 *   a bit more difficult. Complex ops acquire the full lock
312	 *   and first wait that the running simple ops have completed.
313	 *   (see above)
314	 *   Thus: If we own a simple lock and the global lock is free
315	 *	and complex_count is now 0, then it will stay 0 and
316	 *	thus just locking sem->lock is sufficient.
317	 */
318	sem = sma->sem_base + sops->sem_num;
319
320	if (sma->complex_count == 0) {
321		/*
322		 * It appears that no complex operation is around.
323		 * Acquire the per-semaphore lock.
324		 */
325		spin_lock(&sem->lock);
326
327		/* Then check that the global lock is free */
328		if (!spin_is_locked(&sma->sem_perm.lock)) {
329			/* spin_is_locked() is not a memory barrier */
330			smp_mb();
331
332			/* Now repeat the test of complex_count:
333			 * It can't change anymore until we drop sem->lock.
334			 * Thus: if is now 0, then it will stay 0.
335			 */
336			if (sma->complex_count == 0) {
337				/* fast path successful! */
338				return sops->sem_num;
339			}
340		}
341		spin_unlock(&sem->lock);
342	}
343
344	/* slow path: acquire the full lock */
345	ipc_lock_object(&sma->sem_perm);
346
347	if (sma->complex_count == 0) {
348		/* False alarm:
349		 * There is no complex operation, thus we can switch
350		 * back to the fast path.
351		 */
352		spin_lock(&sem->lock);
353		ipc_unlock_object(&sma->sem_perm);
354		return sops->sem_num;
355	} else {
356		/* Not a false alarm, thus complete the sequence for a
357		 * full lock.
358		 */
359		sem_wait_array(sma);
360		return -1;
361	}
362}
363
364static inline void sem_unlock(struct sem_array *sma, int locknum)
365{
366	if (locknum == -1) {
367		unmerge_queues(sma);
368		ipc_unlock_object(&sma->sem_perm);
369	} else {
370		struct sem *sem = sma->sem_base + locknum;
371		spin_unlock(&sem->lock);
372	}
373}
374
375/*
376 * sem_lock_(check_) routines are called in the paths where the rwsem
377 * is not held.
378 *
379 * The caller holds the RCU read lock.
380 */
381static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
382			int id, struct sembuf *sops, int nsops, int *locknum)
383{
384	struct kern_ipc_perm *ipcp;
385	struct sem_array *sma;
386
387	ipcp = ipc_obtain_object(&sem_ids(ns), id);
388	if (IS_ERR(ipcp))
389		return ERR_CAST(ipcp);
390
391	sma = container_of(ipcp, struct sem_array, sem_perm);
392	*locknum = sem_lock(sma, sops, nsops);
393
394	/* ipc_rmid() may have already freed the ID while sem_lock
395	 * was spinning: verify that the structure is still valid
396	 */
397	if (ipc_valid_object(ipcp))
398		return container_of(ipcp, struct sem_array, sem_perm);
399
400	sem_unlock(sma, *locknum);
401	return ERR_PTR(-EINVAL);
402}
403
404static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
405{
406	struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
407
408	if (IS_ERR(ipcp))
409		return ERR_CAST(ipcp);
410
411	return container_of(ipcp, struct sem_array, sem_perm);
412}
413
414static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
415							int id)
416{
417	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
418
419	if (IS_ERR(ipcp))
420		return ERR_CAST(ipcp);
421
422	return container_of(ipcp, struct sem_array, sem_perm);
423}
424
425static inline void sem_lock_and_putref(struct sem_array *sma)
426{
427	sem_lock(sma, NULL, -1);
428	ipc_rcu_putref(sma, ipc_rcu_free);
429}
430
431static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
432{
433	ipc_rmid(&sem_ids(ns), &s->sem_perm);
434}
435
436/*
437 * Lockless wakeup algorithm:
438 * Without the check/retry algorithm a lockless wakeup is possible:
439 * - queue.status is initialized to -EINTR before blocking.
440 * - wakeup is performed by
441 *	* unlinking the queue entry from the pending list
442 *	* setting queue.status to IN_WAKEUP
443 *	  This is the notification for the blocked thread that a
444 *	  result value is imminent.
445 *	* call wake_up_process
446 *	* set queue.status to the final value.
447 * - the previously blocked thread checks queue.status:
448 *	* if it's IN_WAKEUP, then it must wait until the value changes
449 *	* if it's not -EINTR, then the operation was completed by
450 *	  update_queue. semtimedop can return queue.status without
451 *	  performing any operation on the sem array.
452 *	* otherwise it must acquire the spinlock and check what's up.
453 *
454 * The two-stage algorithm is necessary to protect against the following
455 * races:
456 * - if queue.status is set after wake_up_process, then the woken up idle
457 *   thread could race forward and try (and fail) to acquire sma->lock
458 *   before update_queue had a chance to set queue.status
459 * - if queue.status is written before wake_up_process and if the
460 *   blocked process is woken up by a signal between writing
461 *   queue.status and the wake_up_process, then the woken up
462 *   process could return from semtimedop and die by calling
463 *   sys_exit before wake_up_process is called. Then wake_up_process
464 *   will oops, because the task structure is already invalid.
465 *   (yes, this happened on s390 with sysv msg).
466 *
467 */
468#define IN_WAKEUP	1
469
470/**
471 * newary - Create a new semaphore set
472 * @ns: namespace
473 * @params: ptr to the structure that contains key, semflg and nsems
474 *
475 * Called with sem_ids.rwsem held (as a writer)
476 */
477static int newary(struct ipc_namespace *ns, struct ipc_params *params)
478{
479	int id;
480	int retval;
481	struct sem_array *sma;
482	int size;
483	key_t key = params->key;
484	int nsems = params->u.nsems;
485	int semflg = params->flg;
486	int i;
487
488	if (!nsems)
489		return -EINVAL;
490	if (ns->used_sems + nsems > ns->sc_semmns)
491		return -ENOSPC;
492
493	size = sizeof(*sma) + nsems * sizeof(struct sem);
494	sma = ipc_rcu_alloc(size);
495	if (!sma)
496		return -ENOMEM;
497
498	memset(sma, 0, size);
499
500	sma->sem_perm.mode = (semflg & S_IRWXUGO);
501	sma->sem_perm.key = key;
502
503	sma->sem_perm.security = NULL;
504	retval = security_sem_alloc(sma);
505	if (retval) {
506		ipc_rcu_putref(sma, ipc_rcu_free);
507		return retval;
508	}
509
510	id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
511	if (id < 0) {
512		ipc_rcu_putref(sma, sem_rcu_free);
513		return id;
514	}
515	ns->used_sems += nsems;
516
517	sma->sem_base = (struct sem *) &sma[1];
518
519	for (i = 0; i < nsems; i++) {
520		INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
521		INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
522		spin_lock_init(&sma->sem_base[i].lock);
523	}
524
525	sma->complex_count = 0;
526	INIT_LIST_HEAD(&sma->pending_alter);
527	INIT_LIST_HEAD(&sma->pending_const);
528	INIT_LIST_HEAD(&sma->list_id);
529	sma->sem_nsems = nsems;
530	sma->sem_ctime = get_seconds();
531	sem_unlock(sma, -1);
532	rcu_read_unlock();
533
534	return sma->sem_perm.id;
535}
536
537
538/*
539 * Called with sem_ids.rwsem and ipcp locked.
540 */
541static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
542{
543	struct sem_array *sma;
544
545	sma = container_of(ipcp, struct sem_array, sem_perm);
546	return security_sem_associate(sma, semflg);
547}
548
549/*
550 * Called with sem_ids.rwsem and ipcp locked.
551 */
552static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
553				struct ipc_params *params)
554{
555	struct sem_array *sma;
556
557	sma = container_of(ipcp, struct sem_array, sem_perm);
558	if (params->u.nsems > sma->sem_nsems)
559		return -EINVAL;
560
561	return 0;
562}
563
564SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
565{
566	struct ipc_namespace *ns;
567	static const struct ipc_ops sem_ops = {
568		.getnew = newary,
569		.associate = sem_security,
570		.more_checks = sem_more_checks,
571	};
572	struct ipc_params sem_params;
573
574	ns = current->nsproxy->ipc_ns;
575
576	if (nsems < 0 || nsems > ns->sc_semmsl)
577		return -EINVAL;
578
579	sem_params.key = key;
580	sem_params.flg = semflg;
581	sem_params.u.nsems = nsems;
582
583	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
584}
585
586/**
587 * perform_atomic_semop - Perform (if possible) a semaphore operation
588 * @sma: semaphore array
589 * @q: struct sem_queue that describes the operation
590 *
591 * Returns 0 if the operation was possible.
592 * Returns 1 if the operation is impossible, the caller must sleep.
593 * Negative values are error codes.
594 */
595static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
596{
597	int result, sem_op, nsops, pid;
598	struct sembuf *sop;
599	struct sem *curr;
600	struct sembuf *sops;
601	struct sem_undo *un;
602
603	sops = q->sops;
604	nsops = q->nsops;
605	un = q->undo;
606
607	for (sop = sops; sop < sops + nsops; sop++) {
608		curr = sma->sem_base + sop->sem_num;
609		sem_op = sop->sem_op;
610		result = curr->semval;
611
612		if (!sem_op && result)
613			goto would_block;
614
615		result += sem_op;
616		if (result < 0)
617			goto would_block;
618		if (result > SEMVMX)
619			goto out_of_range;
620
621		if (sop->sem_flg & SEM_UNDO) {
622			int undo = un->semadj[sop->sem_num] - sem_op;
623			/* Exceeding the undo range is an error. */
624			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
625				goto out_of_range;
626			un->semadj[sop->sem_num] = undo;
627		}
628
629		curr->semval = result;
630	}
631
632	sop--;
633	pid = q->pid;
634	while (sop >= sops) {
635		sma->sem_base[sop->sem_num].sempid = pid;
636		sop--;
637	}
638
639	return 0;
640
641out_of_range:
642	result = -ERANGE;
643	goto undo;
644
645would_block:
646	q->blocking = sop;
647
648	if (sop->sem_flg & IPC_NOWAIT)
649		result = -EAGAIN;
650	else
651		result = 1;
652
653undo:
654	sop--;
655	while (sop >= sops) {
656		sem_op = sop->sem_op;
657		sma->sem_base[sop->sem_num].semval -= sem_op;
658		if (sop->sem_flg & SEM_UNDO)
659			un->semadj[sop->sem_num] += sem_op;
660		sop--;
661	}
662
663	return result;
664}
665
666/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
667 * @q: queue entry that must be signaled
668 * @error: Error value for the signal
669 *
670 * Prepare the wake-up of the queue entry q.
671 */
672static void wake_up_sem_queue_prepare(struct list_head *pt,
673				struct sem_queue *q, int error)
674{
675	if (list_empty(pt)) {
676		/*
677		 * Hold preempt off so that we don't get preempted and have the
678		 * wakee busy-wait until we're scheduled back on.
679		 */
680		preempt_disable();
681	}
682	q->status = IN_WAKEUP;
683	q->pid = error;
684
685	list_add_tail(&q->list, pt);
686}
687
688/**
689 * wake_up_sem_queue_do - do the actual wake-up
690 * @pt: list of tasks to be woken up
691 *
692 * Do the actual wake-up.
693 * The function is called without any locks held, thus the semaphore array
694 * could be destroyed already and the tasks can disappear as soon as the
695 * status is set to the actual return code.
696 */
697static void wake_up_sem_queue_do(struct list_head *pt)
698{
699	struct sem_queue *q, *t;
700	int did_something;
701
702	did_something = !list_empty(pt);
703	list_for_each_entry_safe(q, t, pt, list) {
704		wake_up_process(q->sleeper);
705		/* q can disappear immediately after writing q->status. */
706		smp_wmb();
707		q->status = q->pid;
708	}
709	if (did_something)
710		preempt_enable();
711}
712
713static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
714{
715	list_del(&q->list);
716	if (q->nsops > 1)
717		sma->complex_count--;
718}
719
720/** check_restart(sma, q)
721 * @sma: semaphore array
722 * @q: the operation that just completed
723 *
724 * update_queue is O(N^2) when it restarts scanning the whole queue of
725 * waiting operations. Therefore this function checks if the restart is
726 * really necessary. It is called after a previously waiting operation
727 * modified the array.
728 * Note that wait-for-zero operations are handled without restart.
729 */
730static int check_restart(struct sem_array *sma, struct sem_queue *q)
731{
732	/* pending complex alter operations are too difficult to analyse */
733	if (!list_empty(&sma->pending_alter))
734		return 1;
735
736	/* we were a sleeping complex operation. Too difficult */
737	if (q->nsops > 1)
738		return 1;
739
740	/* It is impossible that someone waits for the new value:
741	 * - complex operations always restart.
742	 * - wait-for-zero are handled seperately.
743	 * - q is a previously sleeping simple operation that
744	 *   altered the array. It must be a decrement, because
745	 *   simple increments never sleep.
746	 * - If there are older (higher priority) decrements
747	 *   in the queue, then they have observed the original
748	 *   semval value and couldn't proceed. The operation
749	 *   decremented to value - thus they won't proceed either.
750	 */
751	return 0;
752}
753
754/**
755 * wake_const_ops - wake up non-alter tasks
756 * @sma: semaphore array.
757 * @semnum: semaphore that was modified.
758 * @pt: list head for the tasks that must be woken up.
759 *
760 * wake_const_ops must be called after a semaphore in a semaphore array
761 * was set to 0. If complex const operations are pending, wake_const_ops must
762 * be called with semnum = -1, as well as with the number of each modified
763 * semaphore.
764 * The tasks that must be woken up are added to @pt. The return code
765 * is stored in q->pid.
766 * The function returns 1 if at least one operation was completed successfully.
767 */
768static int wake_const_ops(struct sem_array *sma, int semnum,
769				struct list_head *pt)
770{
771	struct sem_queue *q;
772	struct list_head *walk;
773	struct list_head *pending_list;
774	int semop_completed = 0;
775
776	if (semnum == -1)
777		pending_list = &sma->pending_const;
778	else
779		pending_list = &sma->sem_base[semnum].pending_const;
780
781	walk = pending_list->next;
782	while (walk != pending_list) {
783		int error;
784
785		q = container_of(walk, struct sem_queue, list);
786		walk = walk->next;
787
788		error = perform_atomic_semop(sma, q);
789
790		if (error <= 0) {
791			/* operation completed, remove from queue & wakeup */
792
793			unlink_queue(sma, q);
794
795			wake_up_sem_queue_prepare(pt, q, error);
796			if (error == 0)
797				semop_completed = 1;
798		}
799	}
800	return semop_completed;
801}
802
803/**
804 * do_smart_wakeup_zero - wakeup all wait for zero tasks
805 * @sma: semaphore array
806 * @sops: operations that were performed
807 * @nsops: number of operations
808 * @pt: list head of the tasks that must be woken up.
809 *
810 * Checks all required queue for wait-for-zero operations, based
811 * on the actual changes that were performed on the semaphore array.
812 * The function returns 1 if at least one operation was completed successfully.
813 */
814static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
815					int nsops, struct list_head *pt)
816{
817	int i;
818	int semop_completed = 0;
819	int got_zero = 0;
820
821	/* first: the per-semaphore queues, if known */
822	if (sops) {
823		for (i = 0; i < nsops; i++) {
824			int num = sops[i].sem_num;
825
826			if (sma->sem_base[num].semval == 0) {
827				got_zero = 1;
828				semop_completed |= wake_const_ops(sma, num, pt);
829			}
830		}
831	} else {
832		/*
833		 * No sops means modified semaphores not known.
834		 * Assume all were changed.
835		 */
836		for (i = 0; i < sma->sem_nsems; i++) {
837			if (sma->sem_base[i].semval == 0) {
838				got_zero = 1;
839				semop_completed |= wake_const_ops(sma, i, pt);
840			}
841		}
842	}
843	/*
844	 * If one of the modified semaphores got 0,
845	 * then check the global queue, too.
846	 */
847	if (got_zero)
848		semop_completed |= wake_const_ops(sma, -1, pt);
849
850	return semop_completed;
851}
852
853
854/**
855 * update_queue - look for tasks that can be completed.
856 * @sma: semaphore array.
857 * @semnum: semaphore that was modified.
858 * @pt: list head for the tasks that must be woken up.
859 *
860 * update_queue must be called after a semaphore in a semaphore array
861 * was modified. If multiple semaphores were modified, update_queue must
862 * be called with semnum = -1, as well as with the number of each modified
863 * semaphore.
864 * The tasks that must be woken up are added to @pt. The return code
865 * is stored in q->pid.
866 * The function internally checks if const operations can now succeed.
867 *
868 * The function return 1 if at least one semop was completed successfully.
869 */
870static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
871{
872	struct sem_queue *q;
873	struct list_head *walk;
874	struct list_head *pending_list;
875	int semop_completed = 0;
876
877	if (semnum == -1)
878		pending_list = &sma->pending_alter;
879	else
880		pending_list = &sma->sem_base[semnum].pending_alter;
881
882again:
883	walk = pending_list->next;
884	while (walk != pending_list) {
885		int error, restart;
886
887		q = container_of(walk, struct sem_queue, list);
888		walk = walk->next;
889
890		/* If we are scanning the single sop, per-semaphore list of
891		 * one semaphore and that semaphore is 0, then it is not
892		 * necessary to scan further: simple increments
893		 * that affect only one entry succeed immediately and cannot
894		 * be in the  per semaphore pending queue, and decrements
895		 * cannot be successful if the value is already 0.
896		 */
897		if (semnum != -1 && sma->sem_base[semnum].semval == 0)
898			break;
899
900		error = perform_atomic_semop(sma, q);
901
902		/* Does q->sleeper still need to sleep? */
903		if (error > 0)
904			continue;
905
906		unlink_queue(sma, q);
907
908		if (error) {
909			restart = 0;
910		} else {
911			semop_completed = 1;
912			do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
913			restart = check_restart(sma, q);
914		}
915
916		wake_up_sem_queue_prepare(pt, q, error);
917		if (restart)
918			goto again;
919	}
920	return semop_completed;
921}
922
923/**
924 * set_semotime - set sem_otime
925 * @sma: semaphore array
926 * @sops: operations that modified the array, may be NULL
927 *
928 * sem_otime is replicated to avoid cache line trashing.
929 * This function sets one instance to the current time.
930 */
931static void set_semotime(struct sem_array *sma, struct sembuf *sops)
932{
933	if (sops == NULL) {
934		sma->sem_base[0].sem_otime = get_seconds();
935	} else {
936		sma->sem_base[sops[0].sem_num].sem_otime =
937							get_seconds();
938	}
939}
940
941/**
942 * do_smart_update - optimized update_queue
943 * @sma: semaphore array
944 * @sops: operations that were performed
945 * @nsops: number of operations
946 * @otime: force setting otime
947 * @pt: list head of the tasks that must be woken up.
948 *
949 * do_smart_update() does the required calls to update_queue and wakeup_zero,
950 * based on the actual changes that were performed on the semaphore array.
951 * Note that the function does not do the actual wake-up: the caller is
952 * responsible for calling wake_up_sem_queue_do(@pt).
953 * It is safe to perform this call after dropping all locks.
954 */
955static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
956			int otime, struct list_head *pt)
957{
958	int i;
959
960	otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
961
962	if (!list_empty(&sma->pending_alter)) {
963		/* semaphore array uses the global queue - just process it. */
964		otime |= update_queue(sma, -1, pt);
965	} else {
966		if (!sops) {
967			/*
968			 * No sops, thus the modified semaphores are not
969			 * known. Check all.
970			 */
971			for (i = 0; i < sma->sem_nsems; i++)
972				otime |= update_queue(sma, i, pt);
973		} else {
974			/*
975			 * Check the semaphores that were increased:
976			 * - No complex ops, thus all sleeping ops are
977			 *   decrease.
978			 * - if we decreased the value, then any sleeping
979			 *   semaphore ops wont be able to run: If the
980			 *   previous value was too small, then the new
981			 *   value will be too small, too.
982			 */
983			for (i = 0; i < nsops; i++) {
984				if (sops[i].sem_op > 0) {
985					otime |= update_queue(sma,
986							sops[i].sem_num, pt);
987				}
988			}
989		}
990	}
991	if (otime)
992		set_semotime(sma, sops);
993}
994
995/*
996 * check_qop: Test if a queued operation sleeps on the semaphore semnum
997 */
998static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
999			bool count_zero)
1000{
1001	struct sembuf *sop = q->blocking;
1002
1003	/*
1004	 * Linux always (since 0.99.10) reported a task as sleeping on all
1005	 * semaphores. This violates SUS, therefore it was changed to the
1006	 * standard compliant behavior.
1007	 * Give the administrators a chance to notice that an application
1008	 * might misbehave because it relies on the Linux behavior.
1009	 */
1010	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1011			"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1012			current->comm, task_pid_nr(current));
1013
1014	if (sop->sem_num != semnum)
1015		return 0;
1016
1017	if (count_zero && sop->sem_op == 0)
1018		return 1;
1019	if (!count_zero && sop->sem_op < 0)
1020		return 1;
1021
1022	return 0;
1023}
1024
1025/* The following counts are associated to each semaphore:
1026 *   semncnt        number of tasks waiting on semval being nonzero
1027 *   semzcnt        number of tasks waiting on semval being zero
1028 *
1029 * Per definition, a task waits only on the semaphore of the first semop
1030 * that cannot proceed, even if additional operation would block, too.
1031 */
1032static int count_semcnt(struct sem_array *sma, ushort semnum,
1033			bool count_zero)
1034{
1035	struct list_head *l;
1036	struct sem_queue *q;
1037	int semcnt;
1038
1039	semcnt = 0;
1040	/* First: check the simple operations. They are easy to evaluate */
1041	if (count_zero)
1042		l = &sma->sem_base[semnum].pending_const;
1043	else
1044		l = &sma->sem_base[semnum].pending_alter;
1045
1046	list_for_each_entry(q, l, list) {
1047		/* all task on a per-semaphore list sleep on exactly
1048		 * that semaphore
1049		 */
1050		semcnt++;
1051	}
1052
1053	/* Then: check the complex operations. */
1054	list_for_each_entry(q, &sma->pending_alter, list) {
1055		semcnt += check_qop(sma, semnum, q, count_zero);
1056	}
1057	if (count_zero) {
1058		list_for_each_entry(q, &sma->pending_const, list) {
1059			semcnt += check_qop(sma, semnum, q, count_zero);
1060		}
1061	}
1062	return semcnt;
1063}
1064
1065/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1066 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1067 * remains locked on exit.
1068 */
1069static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1070{
1071	struct sem_undo *un, *tu;
1072	struct sem_queue *q, *tq;
1073	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1074	struct list_head tasks;
1075	int i;
1076
1077	/* Free the existing undo structures for this semaphore set.  */
1078	ipc_assert_locked_object(&sma->sem_perm);
1079	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1080		list_del(&un->list_id);
1081		spin_lock(&un->ulp->lock);
1082		un->semid = -1;
1083		list_del_rcu(&un->list_proc);
1084		spin_unlock(&un->ulp->lock);
1085		kfree_rcu(un, rcu);
1086	}
1087
1088	/* Wake up all pending processes and let them fail with EIDRM. */
1089	INIT_LIST_HEAD(&tasks);
1090	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1091		unlink_queue(sma, q);
1092		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1093	}
1094
1095	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1096		unlink_queue(sma, q);
1097		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1098	}
1099	for (i = 0; i < sma->sem_nsems; i++) {
1100		struct sem *sem = sma->sem_base + i;
1101		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1102			unlink_queue(sma, q);
1103			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1104		}
1105		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1106			unlink_queue(sma, q);
1107			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1108		}
1109	}
1110
1111	/* Remove the semaphore set from the IDR */
1112	sem_rmid(ns, sma);
1113	sem_unlock(sma, -1);
1114	rcu_read_unlock();
1115
1116	wake_up_sem_queue_do(&tasks);
1117	ns->used_sems -= sma->sem_nsems;
1118	ipc_rcu_putref(sma, sem_rcu_free);
1119}
1120
1121static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1122{
1123	switch (version) {
1124	case IPC_64:
1125		return copy_to_user(buf, in, sizeof(*in));
1126	case IPC_OLD:
1127	    {
1128		struct semid_ds out;
1129
1130		memset(&out, 0, sizeof(out));
1131
1132		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1133
1134		out.sem_otime	= in->sem_otime;
1135		out.sem_ctime	= in->sem_ctime;
1136		out.sem_nsems	= in->sem_nsems;
1137
1138		return copy_to_user(buf, &out, sizeof(out));
1139	    }
1140	default:
1141		return -EINVAL;
1142	}
1143}
1144
1145static time_t get_semotime(struct sem_array *sma)
1146{
1147	int i;
1148	time_t res;
1149
1150	res = sma->sem_base[0].sem_otime;
1151	for (i = 1; i < sma->sem_nsems; i++) {
1152		time_t to = sma->sem_base[i].sem_otime;
1153
1154		if (to > res)
1155			res = to;
1156	}
1157	return res;
1158}
1159
1160static int semctl_nolock(struct ipc_namespace *ns, int semid,
1161			 int cmd, int version, void __user *p)
1162{
1163	int err;
1164	struct sem_array *sma;
1165
1166	switch (cmd) {
1167	case IPC_INFO:
1168	case SEM_INFO:
1169	{
1170		struct seminfo seminfo;
1171		int max_id;
1172
1173		err = security_sem_semctl(NULL, cmd);
1174		if (err)
1175			return err;
1176
1177		memset(&seminfo, 0, sizeof(seminfo));
1178		seminfo.semmni = ns->sc_semmni;
1179		seminfo.semmns = ns->sc_semmns;
1180		seminfo.semmsl = ns->sc_semmsl;
1181		seminfo.semopm = ns->sc_semopm;
1182		seminfo.semvmx = SEMVMX;
1183		seminfo.semmnu = SEMMNU;
1184		seminfo.semmap = SEMMAP;
1185		seminfo.semume = SEMUME;
1186		down_read(&sem_ids(ns).rwsem);
1187		if (cmd == SEM_INFO) {
1188			seminfo.semusz = sem_ids(ns).in_use;
1189			seminfo.semaem = ns->used_sems;
1190		} else {
1191			seminfo.semusz = SEMUSZ;
1192			seminfo.semaem = SEMAEM;
1193		}
1194		max_id = ipc_get_maxid(&sem_ids(ns));
1195		up_read(&sem_ids(ns).rwsem);
1196		if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1197			return -EFAULT;
1198		return (max_id < 0) ? 0 : max_id;
1199	}
1200	case IPC_STAT:
1201	case SEM_STAT:
1202	{
1203		struct semid64_ds tbuf;
1204		int id = 0;
1205
1206		memset(&tbuf, 0, sizeof(tbuf));
1207
1208		rcu_read_lock();
1209		if (cmd == SEM_STAT) {
1210			sma = sem_obtain_object(ns, semid);
1211			if (IS_ERR(sma)) {
1212				err = PTR_ERR(sma);
1213				goto out_unlock;
1214			}
1215			id = sma->sem_perm.id;
1216		} else {
1217			sma = sem_obtain_object_check(ns, semid);
1218			if (IS_ERR(sma)) {
1219				err = PTR_ERR(sma);
1220				goto out_unlock;
1221			}
1222		}
1223
1224		err = -EACCES;
1225		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1226			goto out_unlock;
1227
1228		err = security_sem_semctl(sma, cmd);
1229		if (err)
1230			goto out_unlock;
1231
1232		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1233		tbuf.sem_otime = get_semotime(sma);
1234		tbuf.sem_ctime = sma->sem_ctime;
1235		tbuf.sem_nsems = sma->sem_nsems;
1236		rcu_read_unlock();
1237		if (copy_semid_to_user(p, &tbuf, version))
1238			return -EFAULT;
1239		return id;
1240	}
1241	default:
1242		return -EINVAL;
1243	}
1244out_unlock:
1245	rcu_read_unlock();
1246	return err;
1247}
1248
1249static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1250		unsigned long arg)
1251{
1252	struct sem_undo *un;
1253	struct sem_array *sma;
1254	struct sem *curr;
1255	int err;
1256	struct list_head tasks;
1257	int val;
1258#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1259	/* big-endian 64bit */
1260	val = arg >> 32;
1261#else
1262	/* 32bit or little-endian 64bit */
1263	val = arg;
1264#endif
1265
1266	if (val > SEMVMX || val < 0)
1267		return -ERANGE;
1268
1269	INIT_LIST_HEAD(&tasks);
1270
1271	rcu_read_lock();
1272	sma = sem_obtain_object_check(ns, semid);
1273	if (IS_ERR(sma)) {
1274		rcu_read_unlock();
1275		return PTR_ERR(sma);
1276	}
1277
1278	if (semnum < 0 || semnum >= sma->sem_nsems) {
1279		rcu_read_unlock();
1280		return -EINVAL;
1281	}
1282
1283
1284	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1285		rcu_read_unlock();
1286		return -EACCES;
1287	}
1288
1289	err = security_sem_semctl(sma, SETVAL);
1290	if (err) {
1291		rcu_read_unlock();
1292		return -EACCES;
1293	}
1294
1295	sem_lock(sma, NULL, -1);
1296
1297	if (!ipc_valid_object(&sma->sem_perm)) {
1298		sem_unlock(sma, -1);
1299		rcu_read_unlock();
1300		return -EIDRM;
1301	}
1302
1303	curr = &sma->sem_base[semnum];
1304
1305	ipc_assert_locked_object(&sma->sem_perm);
1306	list_for_each_entry(un, &sma->list_id, list_id)
1307		un->semadj[semnum] = 0;
1308
1309	curr->semval = val;
1310	curr->sempid = task_tgid_vnr(current);
1311	sma->sem_ctime = get_seconds();
1312	/* maybe some queued-up processes were waiting for this */
1313	do_smart_update(sma, NULL, 0, 0, &tasks);
1314	sem_unlock(sma, -1);
1315	rcu_read_unlock();
1316	wake_up_sem_queue_do(&tasks);
1317	return 0;
1318}
1319
1320static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1321		int cmd, void __user *p)
1322{
1323	struct sem_array *sma;
1324	struct sem *curr;
1325	int err, nsems;
1326	ushort fast_sem_io[SEMMSL_FAST];
1327	ushort *sem_io = fast_sem_io;
1328	struct list_head tasks;
1329
1330	INIT_LIST_HEAD(&tasks);
1331
1332	rcu_read_lock();
1333	sma = sem_obtain_object_check(ns, semid);
1334	if (IS_ERR(sma)) {
1335		rcu_read_unlock();
1336		return PTR_ERR(sma);
1337	}
1338
1339	nsems = sma->sem_nsems;
1340
1341	err = -EACCES;
1342	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1343		goto out_rcu_wakeup;
1344
1345	err = security_sem_semctl(sma, cmd);
1346	if (err)
1347		goto out_rcu_wakeup;
1348
1349	err = -EACCES;
1350	switch (cmd) {
1351	case GETALL:
1352	{
1353		ushort __user *array = p;
1354		int i;
1355
1356		sem_lock(sma, NULL, -1);
1357		if (!ipc_valid_object(&sma->sem_perm)) {
1358			err = -EIDRM;
1359			goto out_unlock;
1360		}
1361		if (nsems > SEMMSL_FAST) {
1362			if (!ipc_rcu_getref(sma)) {
1363				err = -EIDRM;
1364				goto out_unlock;
1365			}
1366			sem_unlock(sma, -1);
1367			rcu_read_unlock();
1368			sem_io = ipc_alloc(sizeof(ushort)*nsems);
1369			if (sem_io == NULL) {
1370				ipc_rcu_putref(sma, ipc_rcu_free);
1371				return -ENOMEM;
1372			}
1373
1374			rcu_read_lock();
1375			sem_lock_and_putref(sma);
1376			if (!ipc_valid_object(&sma->sem_perm)) {
1377				err = -EIDRM;
1378				goto out_unlock;
1379			}
1380		}
1381		for (i = 0; i < sma->sem_nsems; i++)
1382			sem_io[i] = sma->sem_base[i].semval;
1383		sem_unlock(sma, -1);
1384		rcu_read_unlock();
1385		err = 0;
1386		if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1387			err = -EFAULT;
1388		goto out_free;
1389	}
1390	case SETALL:
1391	{
1392		int i;
1393		struct sem_undo *un;
1394
1395		if (!ipc_rcu_getref(sma)) {
1396			err = -EIDRM;
1397			goto out_rcu_wakeup;
1398		}
1399		rcu_read_unlock();
1400
1401		if (nsems > SEMMSL_FAST) {
1402			sem_io = ipc_alloc(sizeof(ushort)*nsems);
1403			if (sem_io == NULL) {
1404				ipc_rcu_putref(sma, ipc_rcu_free);
1405				return -ENOMEM;
1406			}
1407		}
1408
1409		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1410			ipc_rcu_putref(sma, ipc_rcu_free);
1411			err = -EFAULT;
1412			goto out_free;
1413		}
1414
1415		for (i = 0; i < nsems; i++) {
1416			if (sem_io[i] > SEMVMX) {
1417				ipc_rcu_putref(sma, ipc_rcu_free);
1418				err = -ERANGE;
1419				goto out_free;
1420			}
1421		}
1422		rcu_read_lock();
1423		sem_lock_and_putref(sma);
1424		if (!ipc_valid_object(&sma->sem_perm)) {
1425			err = -EIDRM;
1426			goto out_unlock;
1427		}
1428
1429		for (i = 0; i < nsems; i++)
1430			sma->sem_base[i].semval = sem_io[i];
1431
1432		ipc_assert_locked_object(&sma->sem_perm);
1433		list_for_each_entry(un, &sma->list_id, list_id) {
1434			for (i = 0; i < nsems; i++)
1435				un->semadj[i] = 0;
1436		}
1437		sma->sem_ctime = get_seconds();
1438		/* maybe some queued-up processes were waiting for this */
1439		do_smart_update(sma, NULL, 0, 0, &tasks);
1440		err = 0;
1441		goto out_unlock;
1442	}
1443	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1444	}
1445	err = -EINVAL;
1446	if (semnum < 0 || semnum >= nsems)
1447		goto out_rcu_wakeup;
1448
1449	sem_lock(sma, NULL, -1);
1450	if (!ipc_valid_object(&sma->sem_perm)) {
1451		err = -EIDRM;
1452		goto out_unlock;
1453	}
1454	curr = &sma->sem_base[semnum];
1455
1456	switch (cmd) {
1457	case GETVAL:
1458		err = curr->semval;
1459		goto out_unlock;
1460	case GETPID:
1461		err = curr->sempid;
1462		goto out_unlock;
1463	case GETNCNT:
1464		err = count_semcnt(sma, semnum, 0);
1465		goto out_unlock;
1466	case GETZCNT:
1467		err = count_semcnt(sma, semnum, 1);
1468		goto out_unlock;
1469	}
1470
1471out_unlock:
1472	sem_unlock(sma, -1);
1473out_rcu_wakeup:
1474	rcu_read_unlock();
1475	wake_up_sem_queue_do(&tasks);
1476out_free:
1477	if (sem_io != fast_sem_io)
1478		ipc_free(sem_io, sizeof(ushort)*nsems);
1479	return err;
1480}
1481
1482static inline unsigned long
1483copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1484{
1485	switch (version) {
1486	case IPC_64:
1487		if (copy_from_user(out, buf, sizeof(*out)))
1488			return -EFAULT;
1489		return 0;
1490	case IPC_OLD:
1491	    {
1492		struct semid_ds tbuf_old;
1493
1494		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1495			return -EFAULT;
1496
1497		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1498		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1499		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1500
1501		return 0;
1502	    }
1503	default:
1504		return -EINVAL;
1505	}
1506}
1507
1508/*
1509 * This function handles some semctl commands which require the rwsem
1510 * to be held in write mode.
1511 * NOTE: no locks must be held, the rwsem is taken inside this function.
1512 */
1513static int semctl_down(struct ipc_namespace *ns, int semid,
1514		       int cmd, int version, void __user *p)
1515{
1516	struct sem_array *sma;
1517	int err;
1518	struct semid64_ds semid64;
1519	struct kern_ipc_perm *ipcp;
1520
1521	if (cmd == IPC_SET) {
1522		if (copy_semid_from_user(&semid64, p, version))
1523			return -EFAULT;
1524	}
1525
1526	down_write(&sem_ids(ns).rwsem);
1527	rcu_read_lock();
1528
1529	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1530				      &semid64.sem_perm, 0);
1531	if (IS_ERR(ipcp)) {
1532		err = PTR_ERR(ipcp);
1533		goto out_unlock1;
1534	}
1535
1536	sma = container_of(ipcp, struct sem_array, sem_perm);
1537
1538	err = security_sem_semctl(sma, cmd);
1539	if (err)
1540		goto out_unlock1;
1541
1542	switch (cmd) {
1543	case IPC_RMID:
1544		sem_lock(sma, NULL, -1);
1545		/* freeary unlocks the ipc object and rcu */
1546		freeary(ns, ipcp);
1547		goto out_up;
1548	case IPC_SET:
1549		sem_lock(sma, NULL, -1);
1550		err = ipc_update_perm(&semid64.sem_perm, ipcp);
1551		if (err)
1552			goto out_unlock0;
1553		sma->sem_ctime = get_seconds();
1554		break;
1555	default:
1556		err = -EINVAL;
1557		goto out_unlock1;
1558	}
1559
1560out_unlock0:
1561	sem_unlock(sma, -1);
1562out_unlock1:
1563	rcu_read_unlock();
1564out_up:
1565	up_write(&sem_ids(ns).rwsem);
1566	return err;
1567}
1568
1569SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1570{
1571	int version;
1572	struct ipc_namespace *ns;
1573	void __user *p = (void __user *)arg;
1574
1575	if (semid < 0)
1576		return -EINVAL;
1577
1578	version = ipc_parse_version(&cmd);
1579	ns = current->nsproxy->ipc_ns;
1580
1581	switch (cmd) {
1582	case IPC_INFO:
1583	case SEM_INFO:
1584	case IPC_STAT:
1585	case SEM_STAT:
1586		return semctl_nolock(ns, semid, cmd, version, p);
1587	case GETALL:
1588	case GETVAL:
1589	case GETPID:
1590	case GETNCNT:
1591	case GETZCNT:
1592	case SETALL:
1593		return semctl_main(ns, semid, semnum, cmd, p);
1594	case SETVAL:
1595		return semctl_setval(ns, semid, semnum, arg);
1596	case IPC_RMID:
1597	case IPC_SET:
1598		return semctl_down(ns, semid, cmd, version, p);
1599	default:
1600		return -EINVAL;
1601	}
1602}
1603
1604/* If the task doesn't already have a undo_list, then allocate one
1605 * here.  We guarantee there is only one thread using this undo list,
1606 * and current is THE ONE
1607 *
1608 * If this allocation and assignment succeeds, but later
1609 * portions of this code fail, there is no need to free the sem_undo_list.
1610 * Just let it stay associated with the task, and it'll be freed later
1611 * at exit time.
1612 *
1613 * This can block, so callers must hold no locks.
1614 */
1615static inline int get_undo_list(struct sem_undo_list **undo_listp)
1616{
1617	struct sem_undo_list *undo_list;
1618
1619	undo_list = current->sysvsem.undo_list;
1620	if (!undo_list) {
1621		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1622		if (undo_list == NULL)
1623			return -ENOMEM;
1624		spin_lock_init(&undo_list->lock);
1625		atomic_set(&undo_list->refcnt, 1);
1626		INIT_LIST_HEAD(&undo_list->list_proc);
1627
1628		current->sysvsem.undo_list = undo_list;
1629	}
1630	*undo_listp = undo_list;
1631	return 0;
1632}
1633
1634static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1635{
1636	struct sem_undo *un;
1637
1638	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1639		if (un->semid == semid)
1640			return un;
1641	}
1642	return NULL;
1643}
1644
1645static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1646{
1647	struct sem_undo *un;
1648
1649	assert_spin_locked(&ulp->lock);
1650
1651	un = __lookup_undo(ulp, semid);
1652	if (un) {
1653		list_del_rcu(&un->list_proc);
1654		list_add_rcu(&un->list_proc, &ulp->list_proc);
1655	}
1656	return un;
1657}
1658
1659/**
1660 * find_alloc_undo - lookup (and if not present create) undo array
1661 * @ns: namespace
1662 * @semid: semaphore array id
1663 *
1664 * The function looks up (and if not present creates) the undo structure.
1665 * The size of the undo structure depends on the size of the semaphore
1666 * array, thus the alloc path is not that straightforward.
1667 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1668 * performs a rcu_read_lock().
1669 */
1670static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1671{
1672	struct sem_array *sma;
1673	struct sem_undo_list *ulp;
1674	struct sem_undo *un, *new;
1675	int nsems, error;
1676
1677	error = get_undo_list(&ulp);
1678	if (error)
1679		return ERR_PTR(error);
1680
1681	rcu_read_lock();
1682	spin_lock(&ulp->lock);
1683	un = lookup_undo(ulp, semid);
1684	spin_unlock(&ulp->lock);
1685	if (likely(un != NULL))
1686		goto out;
1687
1688	/* no undo structure around - allocate one. */
1689	/* step 1: figure out the size of the semaphore array */
1690	sma = sem_obtain_object_check(ns, semid);
1691	if (IS_ERR(sma)) {
1692		rcu_read_unlock();
1693		return ERR_CAST(sma);
1694	}
1695
1696	nsems = sma->sem_nsems;
1697	if (!ipc_rcu_getref(sma)) {
1698		rcu_read_unlock();
1699		un = ERR_PTR(-EIDRM);
1700		goto out;
1701	}
1702	rcu_read_unlock();
1703
1704	/* step 2: allocate new undo structure */
1705	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1706	if (!new) {
1707		ipc_rcu_putref(sma, ipc_rcu_free);
1708		return ERR_PTR(-ENOMEM);
1709	}
1710
1711	/* step 3: Acquire the lock on semaphore array */
1712	rcu_read_lock();
1713	sem_lock_and_putref(sma);
1714	if (!ipc_valid_object(&sma->sem_perm)) {
1715		sem_unlock(sma, -1);
1716		rcu_read_unlock();
1717		kfree(new);
1718		un = ERR_PTR(-EIDRM);
1719		goto out;
1720	}
1721	spin_lock(&ulp->lock);
1722
1723	/*
1724	 * step 4: check for races: did someone else allocate the undo struct?
1725	 */
1726	un = lookup_undo(ulp, semid);
1727	if (un) {
1728		kfree(new);
1729		goto success;
1730	}
1731	/* step 5: initialize & link new undo structure */
1732	new->semadj = (short *) &new[1];
1733	new->ulp = ulp;
1734	new->semid = semid;
1735	assert_spin_locked(&ulp->lock);
1736	list_add_rcu(&new->list_proc, &ulp->list_proc);
1737	ipc_assert_locked_object(&sma->sem_perm);
1738	list_add(&new->list_id, &sma->list_id);
1739	un = new;
1740
1741success:
1742	spin_unlock(&ulp->lock);
1743	sem_unlock(sma, -1);
1744out:
1745	return un;
1746}
1747
1748
1749/**
1750 * get_queue_result - retrieve the result code from sem_queue
1751 * @q: Pointer to queue structure
1752 *
1753 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1754 * q->status, then we must loop until the value is replaced with the final
1755 * value: This may happen if a task is woken up by an unrelated event (e.g.
1756 * signal) and in parallel the task is woken up by another task because it got
1757 * the requested semaphores.
1758 *
1759 * The function can be called with or without holding the semaphore spinlock.
1760 */
1761static int get_queue_result(struct sem_queue *q)
1762{
1763	int error;
1764
1765	error = q->status;
1766	while (unlikely(error == IN_WAKEUP)) {
1767		cpu_relax();
1768		error = q->status;
1769	}
1770
1771	return error;
1772}
1773
1774SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1775		unsigned, nsops, const struct timespec __user *, timeout)
1776{
1777	int error = -EINVAL;
1778	struct sem_array *sma;
1779	struct sembuf fast_sops[SEMOPM_FAST];
1780	struct sembuf *sops = fast_sops, *sop;
1781	struct sem_undo *un;
1782	int undos = 0, alter = 0, max, locknum;
1783	struct sem_queue queue;
1784	unsigned long jiffies_left = 0;
1785	struct ipc_namespace *ns;
1786	struct list_head tasks;
1787
1788	ns = current->nsproxy->ipc_ns;
1789
1790	if (nsops < 1 || semid < 0)
1791		return -EINVAL;
1792	if (nsops > ns->sc_semopm)
1793		return -E2BIG;
1794	if (nsops > SEMOPM_FAST) {
1795		sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
1796		if (sops == NULL)
1797			return -ENOMEM;
1798	}
1799	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1800		error =  -EFAULT;
1801		goto out_free;
1802	}
1803	if (timeout) {
1804		struct timespec _timeout;
1805		if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1806			error = -EFAULT;
1807			goto out_free;
1808		}
1809		if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1810			_timeout.tv_nsec >= 1000000000L) {
1811			error = -EINVAL;
1812			goto out_free;
1813		}
1814		jiffies_left = timespec_to_jiffies(&_timeout);
1815	}
1816	max = 0;
1817	for (sop = sops; sop < sops + nsops; sop++) {
1818		if (sop->sem_num >= max)
1819			max = sop->sem_num;
1820		if (sop->sem_flg & SEM_UNDO)
1821			undos = 1;
1822		if (sop->sem_op != 0)
1823			alter = 1;
1824	}
1825
1826	INIT_LIST_HEAD(&tasks);
1827
1828	if (undos) {
1829		/* On success, find_alloc_undo takes the rcu_read_lock */
1830		un = find_alloc_undo(ns, semid);
1831		if (IS_ERR(un)) {
1832			error = PTR_ERR(un);
1833			goto out_free;
1834		}
1835	} else {
1836		un = NULL;
1837		rcu_read_lock();
1838	}
1839
1840	sma = sem_obtain_object_check(ns, semid);
1841	if (IS_ERR(sma)) {
1842		rcu_read_unlock();
1843		error = PTR_ERR(sma);
1844		goto out_free;
1845	}
1846
1847	error = -EFBIG;
1848	if (max >= sma->sem_nsems)
1849		goto out_rcu_wakeup;
1850
1851	error = -EACCES;
1852	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1853		goto out_rcu_wakeup;
1854
1855	error = security_sem_semop(sma, sops, nsops, alter);
1856	if (error)
1857		goto out_rcu_wakeup;
1858
1859	error = -EIDRM;
1860	locknum = sem_lock(sma, sops, nsops);
1861	/*
1862	 * We eventually might perform the following check in a lockless
1863	 * fashion, considering ipc_valid_object() locking constraints.
1864	 * If nsops == 1 and there is no contention for sem_perm.lock, then
1865	 * only a per-semaphore lock is held and it's OK to proceed with the
1866	 * check below. More details on the fine grained locking scheme
1867	 * entangled here and why it's RMID race safe on comments at sem_lock()
1868	 */
1869	if (!ipc_valid_object(&sma->sem_perm))
1870		goto out_unlock_free;
1871	/*
1872	 * semid identifiers are not unique - find_alloc_undo may have
1873	 * allocated an undo structure, it was invalidated by an RMID
1874	 * and now a new array with received the same id. Check and fail.
1875	 * This case can be detected checking un->semid. The existence of
1876	 * "un" itself is guaranteed by rcu.
1877	 */
1878	if (un && un->semid == -1)
1879		goto out_unlock_free;
1880
1881	queue.sops = sops;
1882	queue.nsops = nsops;
1883	queue.undo = un;
1884	queue.pid = task_tgid_vnr(current);
1885	queue.alter = alter;
1886
1887	error = perform_atomic_semop(sma, &queue);
1888	if (error == 0) {
1889		/* If the operation was successful, then do
1890		 * the required updates.
1891		 */
1892		if (alter)
1893			do_smart_update(sma, sops, nsops, 1, &tasks);
1894		else
1895			set_semotime(sma, sops);
1896	}
1897	if (error <= 0)
1898		goto out_unlock_free;
1899
1900	/* We need to sleep on this operation, so we put the current
1901	 * task into the pending queue and go to sleep.
1902	 */
1903
1904	if (nsops == 1) {
1905		struct sem *curr;
1906		curr = &sma->sem_base[sops->sem_num];
1907
1908		if (alter) {
1909			if (sma->complex_count) {
1910				list_add_tail(&queue.list,
1911						&sma->pending_alter);
1912			} else {
1913
1914				list_add_tail(&queue.list,
1915						&curr->pending_alter);
1916			}
1917		} else {
1918			list_add_tail(&queue.list, &curr->pending_const);
1919		}
1920	} else {
1921		if (!sma->complex_count)
1922			merge_queues(sma);
1923
1924		if (alter)
1925			list_add_tail(&queue.list, &sma->pending_alter);
1926		else
1927			list_add_tail(&queue.list, &sma->pending_const);
1928
1929		sma->complex_count++;
1930	}
1931
1932	queue.status = -EINTR;
1933	queue.sleeper = current;
1934
1935sleep_again:
1936	current->state = TASK_INTERRUPTIBLE;
1937	sem_unlock(sma, locknum);
1938	rcu_read_unlock();
1939
1940	if (timeout)
1941		jiffies_left = schedule_timeout(jiffies_left);
1942	else
1943		schedule();
1944
1945	error = get_queue_result(&queue);
1946
1947	if (error != -EINTR) {
1948		/* fast path: update_queue already obtained all requested
1949		 * resources.
1950		 * Perform a smp_mb(): User space could assume that semop()
1951		 * is a memory barrier: Without the mb(), the cpu could
1952		 * speculatively read in user space stale data that was
1953		 * overwritten by the previous owner of the semaphore.
1954		 */
1955		smp_mb();
1956
1957		goto out_free;
1958	}
1959
1960	rcu_read_lock();
1961	sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1962
1963	/*
1964	 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1965	 */
1966	error = get_queue_result(&queue);
1967
1968	/*
1969	 * Array removed? If yes, leave without sem_unlock().
1970	 */
1971	if (IS_ERR(sma)) {
1972		rcu_read_unlock();
1973		goto out_free;
1974	}
1975
1976
1977	/*
1978	 * If queue.status != -EINTR we are woken up by another process.
1979	 * Leave without unlink_queue(), but with sem_unlock().
1980	 */
1981	if (error != -EINTR)
1982		goto out_unlock_free;
1983
1984	/*
1985	 * If an interrupt occurred we have to clean up the queue
1986	 */
1987	if (timeout && jiffies_left == 0)
1988		error = -EAGAIN;
1989
1990	/*
1991	 * If the wakeup was spurious, just retry
1992	 */
1993	if (error == -EINTR && !signal_pending(current))
1994		goto sleep_again;
1995
1996	unlink_queue(sma, &queue);
1997
1998out_unlock_free:
1999	sem_unlock(sma, locknum);
2000out_rcu_wakeup:
2001	rcu_read_unlock();
2002	wake_up_sem_queue_do(&tasks);
2003out_free:
2004	if (sops != fast_sops)
2005		kfree(sops);
2006	return error;
2007}
2008
2009SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2010		unsigned, nsops)
2011{
2012	return sys_semtimedop(semid, tsops, nsops, NULL);
2013}
2014
2015/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2016 * parent and child tasks.
2017 */
2018
2019int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2020{
2021	struct sem_undo_list *undo_list;
2022	int error;
2023
2024	if (clone_flags & CLONE_SYSVSEM) {
2025		error = get_undo_list(&undo_list);
2026		if (error)
2027			return error;
2028		atomic_inc(&undo_list->refcnt);
2029		tsk->sysvsem.undo_list = undo_list;
2030	} else
2031		tsk->sysvsem.undo_list = NULL;
2032
2033	return 0;
2034}
2035
2036/*
2037 * add semadj values to semaphores, free undo structures.
2038 * undo structures are not freed when semaphore arrays are destroyed
2039 * so some of them may be out of date.
2040 * IMPLEMENTATION NOTE: There is some confusion over whether the
2041 * set of adjustments that needs to be done should be done in an atomic
2042 * manner or not. That is, if we are attempting to decrement the semval
2043 * should we queue up and wait until we can do so legally?
2044 * The original implementation attempted to do this (queue and wait).
2045 * The current implementation does not do so. The POSIX standard
2046 * and SVID should be consulted to determine what behavior is mandated.
2047 */
2048void exit_sem(struct task_struct *tsk)
2049{
2050	struct sem_undo_list *ulp;
2051
2052	ulp = tsk->sysvsem.undo_list;
2053	if (!ulp)
2054		return;
2055	tsk->sysvsem.undo_list = NULL;
2056
2057	if (!atomic_dec_and_test(&ulp->refcnt))
2058		return;
2059
2060	for (;;) {
2061		struct sem_array *sma;
2062		struct sem_undo *un;
2063		struct list_head tasks;
2064		int semid, i;
2065
2066		rcu_read_lock();
2067		un = list_entry_rcu(ulp->list_proc.next,
2068				    struct sem_undo, list_proc);
2069		if (&un->list_proc == &ulp->list_proc)
2070			semid = -1;
2071		 else
2072			semid = un->semid;
2073
2074		if (semid == -1) {
2075			rcu_read_unlock();
2076			break;
2077		}
2078
2079		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
2080		/* exit_sem raced with IPC_RMID, nothing to do */
2081		if (IS_ERR(sma)) {
2082			rcu_read_unlock();
2083			continue;
2084		}
2085
2086		sem_lock(sma, NULL, -1);
2087		/* exit_sem raced with IPC_RMID, nothing to do */
2088		if (!ipc_valid_object(&sma->sem_perm)) {
2089			sem_unlock(sma, -1);
2090			rcu_read_unlock();
2091			continue;
2092		}
2093		un = __lookup_undo(ulp, semid);
2094		if (un == NULL) {
2095			/* exit_sem raced with IPC_RMID+semget() that created
2096			 * exactly the same semid. Nothing to do.
2097			 */
2098			sem_unlock(sma, -1);
2099			rcu_read_unlock();
2100			continue;
2101		}
2102
2103		/* remove un from the linked lists */
2104		ipc_assert_locked_object(&sma->sem_perm);
2105		list_del(&un->list_id);
2106
2107		spin_lock(&ulp->lock);
2108		list_del_rcu(&un->list_proc);
2109		spin_unlock(&ulp->lock);
2110
2111		/* perform adjustments registered in un */
2112		for (i = 0; i < sma->sem_nsems; i++) {
2113			struct sem *semaphore = &sma->sem_base[i];
2114			if (un->semadj[i]) {
2115				semaphore->semval += un->semadj[i];
2116				/*
2117				 * Range checks of the new semaphore value,
2118				 * not defined by sus:
2119				 * - Some unices ignore the undo entirely
2120				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2121				 * - some cap the value (e.g. FreeBSD caps
2122				 *   at 0, but doesn't enforce SEMVMX)
2123				 *
2124				 * Linux caps the semaphore value, both at 0
2125				 * and at SEMVMX.
2126				 *
2127				 *	Manfred <manfred@colorfullife.com>
2128				 */
2129				if (semaphore->semval < 0)
2130					semaphore->semval = 0;
2131				if (semaphore->semval > SEMVMX)
2132					semaphore->semval = SEMVMX;
2133				semaphore->sempid = task_tgid_vnr(current);
2134			}
2135		}
2136		/* maybe some queued-up processes were waiting for this */
2137		INIT_LIST_HEAD(&tasks);
2138		do_smart_update(sma, NULL, 0, 1, &tasks);
2139		sem_unlock(sma, -1);
2140		rcu_read_unlock();
2141		wake_up_sem_queue_do(&tasks);
2142
2143		kfree_rcu(un, rcu);
2144	}
2145	kfree(ulp);
2146}
2147
2148#ifdef CONFIG_PROC_FS
2149static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2150{
2151	struct user_namespace *user_ns = seq_user_ns(s);
2152	struct sem_array *sma = it;
2153	time_t sem_otime;
2154
2155	/*
2156	 * The proc interface isn't aware of sem_lock(), it calls
2157	 * ipc_lock_object() directly (in sysvipc_find_ipc).
2158	 * In order to stay compatible with sem_lock(), we must wait until
2159	 * all simple semop() calls have left their critical regions.
2160	 */
2161	sem_wait_array(sma);
2162
2163	sem_otime = get_semotime(sma);
2164
2165	return seq_printf(s,
2166			  "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2167			  sma->sem_perm.key,
2168			  sma->sem_perm.id,
2169			  sma->sem_perm.mode,
2170			  sma->sem_nsems,
2171			  from_kuid_munged(user_ns, sma->sem_perm.uid),
2172			  from_kgid_munged(user_ns, sma->sem_perm.gid),
2173			  from_kuid_munged(user_ns, sma->sem_perm.cuid),
2174			  from_kgid_munged(user_ns, sma->sem_perm.cgid),
2175			  sem_otime,
2176			  sma->sem_ctime);
2177}
2178#endif
2179