sem.c revision 0b0577f6
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_semncnt() and
51 *   count_semzcnt()
52 * - the task that performs a successful semop() scans the list of all
53 *   sleeping tasks and completes any pending operations that can be fulfilled.
54 *   Semaphores are actively given to waiting tasks (necessary for FIFO).
55 *   (see update_queue())
56 * - To improve the scalability, the actual wake-up calls are performed after
57 *   dropping all locks. (see wake_up_sem_queue_prepare(),
58 *   wake_up_sem_queue_do())
59 * - All work is done by the waker, the woken up task does not have to do
60 *   anything - not even acquiring a lock or dropping a refcount.
61 * - A woken up task may not even touch the semaphore array anymore, it may
62 *   have been destroyed already by a semctl(RMID).
63 * - The synchronizations between wake-ups due to a timeout/signal and a
64 *   wake-up due to a completed semaphore operation is achieved by using an
65 *   intermediate state (IN_WAKEUP).
66 * - UNDO values are stored in an array (one per process and per
67 *   semaphore array, lazily allocated). For backwards compatibility, multiple
68 *   modes for the UNDO variables are supported (per process, per thread)
69 *   (see copy_semundo, CLONE_SYSVSEM)
70 * - There are two lists of the pending operations: a per-array list
71 *   and per-semaphore list (stored in the array). This allows to achieve FIFO
72 *   ordering without always scanning all pending operations.
73 *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
74 */
75
76#include <linux/slab.h>
77#include <linux/spinlock.h>
78#include <linux/init.h>
79#include <linux/proc_fs.h>
80#include <linux/time.h>
81#include <linux/security.h>
82#include <linux/syscalls.h>
83#include <linux/audit.h>
84#include <linux/capability.h>
85#include <linux/seq_file.h>
86#include <linux/rwsem.h>
87#include <linux/nsproxy.h>
88#include <linux/ipc_namespace.h>
89
90#include <asm/uaccess.h>
91#include "util.h"
92
93#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
94
95#define sem_unlock(sma)		ipc_unlock(&(sma)->sem_perm)
96#define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
97
98static int newary(struct ipc_namespace *, struct ipc_params *);
99static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
100#ifdef CONFIG_PROC_FS
101static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
102#endif
103
104#define SEMMSL_FAST	256 /* 512 bytes on stack */
105#define SEMOPM_FAST	64  /* ~ 372 bytes on stack */
106
107/*
108 * linked list protection:
109 *	sem_undo.id_next,
110 *	sem_array.sem_pending{,last},
111 *	sem_array.sem_undo: sem_lock() for read/write
112 *	sem_undo.proc_next: only "current" is allowed to read/write that field.
113 *
114 */
115
116#define sc_semmsl	sem_ctls[0]
117#define sc_semmns	sem_ctls[1]
118#define sc_semopm	sem_ctls[2]
119#define sc_semmni	sem_ctls[3]
120
121void sem_init_ns(struct ipc_namespace *ns)
122{
123	ns->sc_semmsl = SEMMSL;
124	ns->sc_semmns = SEMMNS;
125	ns->sc_semopm = SEMOPM;
126	ns->sc_semmni = SEMMNI;
127	ns->used_sems = 0;
128	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
129}
130
131#ifdef CONFIG_IPC_NS
132void sem_exit_ns(struct ipc_namespace *ns)
133{
134	free_ipcs(ns, &sem_ids(ns), freeary);
135	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
136}
137#endif
138
139void __init sem_init (void)
140{
141	sem_init_ns(&init_ipc_ns);
142	ipc_init_proc_interface("sysvipc/sem",
143				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
144				IPC_SEM_IDS, sysvipc_sem_proc_show);
145}
146
147/*
148 * sem_lock_(check_) routines are called in the paths where the rw_mutex
149 * is not held.
150 */
151static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
152{
153	struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
154
155	if (IS_ERR(ipcp))
156		return (struct sem_array *)ipcp;
157
158	return container_of(ipcp, struct sem_array, sem_perm);
159}
160
161static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
162						int id)
163{
164	struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
165
166	if (IS_ERR(ipcp))
167		return (struct sem_array *)ipcp;
168
169	return container_of(ipcp, struct sem_array, sem_perm);
170}
171
172static inline void sem_lock_and_putref(struct sem_array *sma)
173{
174	ipc_lock_by_ptr(&sma->sem_perm);
175	ipc_rcu_putref(sma);
176}
177
178static inline void sem_getref_and_unlock(struct sem_array *sma)
179{
180	ipc_rcu_getref(sma);
181	ipc_unlock(&(sma)->sem_perm);
182}
183
184static inline void sem_putref(struct sem_array *sma)
185{
186	ipc_lock_by_ptr(&sma->sem_perm);
187	ipc_rcu_putref(sma);
188	ipc_unlock(&(sma)->sem_perm);
189}
190
191static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
192{
193	ipc_rmid(&sem_ids(ns), &s->sem_perm);
194}
195
196/*
197 * Lockless wakeup algorithm:
198 * Without the check/retry algorithm a lockless wakeup is possible:
199 * - queue.status is initialized to -EINTR before blocking.
200 * - wakeup is performed by
201 *	* unlinking the queue entry from sma->sem_pending
202 *	* setting queue.status to IN_WAKEUP
203 *	  This is the notification for the blocked thread that a
204 *	  result value is imminent.
205 *	* call wake_up_process
206 *	* set queue.status to the final value.
207 * - the previously blocked thread checks queue.status:
208 *   	* if it's IN_WAKEUP, then it must wait until the value changes
209 *   	* if it's not -EINTR, then the operation was completed by
210 *   	  update_queue. semtimedop can return queue.status without
211 *   	  performing any operation on the sem array.
212 *   	* otherwise it must acquire the spinlock and check what's up.
213 *
214 * The two-stage algorithm is necessary to protect against the following
215 * races:
216 * - if queue.status is set after wake_up_process, then the woken up idle
217 *   thread could race forward and try (and fail) to acquire sma->lock
218 *   before update_queue had a chance to set queue.status
219 * - if queue.status is written before wake_up_process and if the
220 *   blocked process is woken up by a signal between writing
221 *   queue.status and the wake_up_process, then the woken up
222 *   process could return from semtimedop and die by calling
223 *   sys_exit before wake_up_process is called. Then wake_up_process
224 *   will oops, because the task structure is already invalid.
225 *   (yes, this happened on s390 with sysv msg).
226 *
227 */
228#define IN_WAKEUP	1
229
230/**
231 * newary - Create a new semaphore set
232 * @ns: namespace
233 * @params: ptr to the structure that contains key, semflg and nsems
234 *
235 * Called with sem_ids.rw_mutex held (as a writer)
236 */
237
238static int newary(struct ipc_namespace *ns, struct ipc_params *params)
239{
240	int id;
241	int retval;
242	struct sem_array *sma;
243	int size;
244	key_t key = params->key;
245	int nsems = params->u.nsems;
246	int semflg = params->flg;
247	int i;
248
249	if (!nsems)
250		return -EINVAL;
251	if (ns->used_sems + nsems > ns->sc_semmns)
252		return -ENOSPC;
253
254	size = sizeof (*sma) + nsems * sizeof (struct sem);
255	sma = ipc_rcu_alloc(size);
256	if (!sma) {
257		return -ENOMEM;
258	}
259	memset (sma, 0, size);
260
261	sma->sem_perm.mode = (semflg & S_IRWXUGO);
262	sma->sem_perm.key = key;
263
264	sma->sem_perm.security = NULL;
265	retval = security_sem_alloc(sma);
266	if (retval) {
267		ipc_rcu_putref(sma);
268		return retval;
269	}
270
271	id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
272	if (id < 0) {
273		security_sem_free(sma);
274		ipc_rcu_putref(sma);
275		return id;
276	}
277	ns->used_sems += nsems;
278
279	sma->sem_base = (struct sem *) &sma[1];
280
281	for (i = 0; i < nsems; i++)
282		INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
283
284	sma->complex_count = 0;
285	INIT_LIST_HEAD(&sma->sem_pending);
286	INIT_LIST_HEAD(&sma->list_id);
287	sma->sem_nsems = nsems;
288	sma->sem_ctime = get_seconds();
289	sem_unlock(sma);
290
291	return sma->sem_perm.id;
292}
293
294
295/*
296 * Called with sem_ids.rw_mutex and ipcp locked.
297 */
298static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
299{
300	struct sem_array *sma;
301
302	sma = container_of(ipcp, struct sem_array, sem_perm);
303	return security_sem_associate(sma, semflg);
304}
305
306/*
307 * Called with sem_ids.rw_mutex and ipcp locked.
308 */
309static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
310				struct ipc_params *params)
311{
312	struct sem_array *sma;
313
314	sma = container_of(ipcp, struct sem_array, sem_perm);
315	if (params->u.nsems > sma->sem_nsems)
316		return -EINVAL;
317
318	return 0;
319}
320
321SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
322{
323	struct ipc_namespace *ns;
324	struct ipc_ops sem_ops;
325	struct ipc_params sem_params;
326
327	ns = current->nsproxy->ipc_ns;
328
329	if (nsems < 0 || nsems > ns->sc_semmsl)
330		return -EINVAL;
331
332	sem_ops.getnew = newary;
333	sem_ops.associate = sem_security;
334	sem_ops.more_checks = sem_more_checks;
335
336	sem_params.key = key;
337	sem_params.flg = semflg;
338	sem_params.u.nsems = nsems;
339
340	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
341}
342
343/*
344 * Determine whether a sequence of semaphore operations would succeed
345 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
346 */
347
348static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
349			     int nsops, struct sem_undo *un, int pid)
350{
351	int result, sem_op;
352	struct sembuf *sop;
353	struct sem * curr;
354
355	for (sop = sops; sop < sops + nsops; sop++) {
356		curr = sma->sem_base + sop->sem_num;
357		sem_op = sop->sem_op;
358		result = curr->semval;
359
360		if (!sem_op && result)
361			goto would_block;
362
363		result += sem_op;
364		if (result < 0)
365			goto would_block;
366		if (result > SEMVMX)
367			goto out_of_range;
368		if (sop->sem_flg & SEM_UNDO) {
369			int undo = un->semadj[sop->sem_num] - sem_op;
370			/*
371	 		 *	Exceeding the undo range is an error.
372			 */
373			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
374				goto out_of_range;
375		}
376		curr->semval = result;
377	}
378
379	sop--;
380	while (sop >= sops) {
381		sma->sem_base[sop->sem_num].sempid = pid;
382		if (sop->sem_flg & SEM_UNDO)
383			un->semadj[sop->sem_num] -= sop->sem_op;
384		sop--;
385	}
386
387	return 0;
388
389out_of_range:
390	result = -ERANGE;
391	goto undo;
392
393would_block:
394	if (sop->sem_flg & IPC_NOWAIT)
395		result = -EAGAIN;
396	else
397		result = 1;
398
399undo:
400	sop--;
401	while (sop >= sops) {
402		sma->sem_base[sop->sem_num].semval -= sop->sem_op;
403		sop--;
404	}
405
406	return result;
407}
408
409/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
410 * @q: queue entry that must be signaled
411 * @error: Error value for the signal
412 *
413 * Prepare the wake-up of the queue entry q.
414 */
415static void wake_up_sem_queue_prepare(struct list_head *pt,
416				struct sem_queue *q, int error)
417{
418	if (list_empty(pt)) {
419		/*
420		 * Hold preempt off so that we don't get preempted and have the
421		 * wakee busy-wait until we're scheduled back on.
422		 */
423		preempt_disable();
424	}
425	q->status = IN_WAKEUP;
426	q->pid = error;
427
428	list_add_tail(&q->simple_list, pt);
429}
430
431/**
432 * wake_up_sem_queue_do(pt) - do the actual wake-up
433 * @pt: list of tasks to be woken up
434 *
435 * Do the actual wake-up.
436 * The function is called without any locks held, thus the semaphore array
437 * could be destroyed already and the tasks can disappear as soon as the
438 * status is set to the actual return code.
439 */
440static void wake_up_sem_queue_do(struct list_head *pt)
441{
442	struct sem_queue *q, *t;
443	int did_something;
444
445	did_something = !list_empty(pt);
446	list_for_each_entry_safe(q, t, pt, simple_list) {
447		wake_up_process(q->sleeper);
448		/* q can disappear immediately after writing q->status. */
449		smp_wmb();
450		q->status = q->pid;
451	}
452	if (did_something)
453		preempt_enable();
454}
455
456static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
457{
458	list_del(&q->list);
459	if (q->nsops == 1)
460		list_del(&q->simple_list);
461	else
462		sma->complex_count--;
463}
464
465/** check_restart(sma, q)
466 * @sma: semaphore array
467 * @q: the operation that just completed
468 *
469 * update_queue is O(N^2) when it restarts scanning the whole queue of
470 * waiting operations. Therefore this function checks if the restart is
471 * really necessary. It is called after a previously waiting operation
472 * was completed.
473 */
474static int check_restart(struct sem_array *sma, struct sem_queue *q)
475{
476	struct sem *curr;
477	struct sem_queue *h;
478
479	/* if the operation didn't modify the array, then no restart */
480	if (q->alter == 0)
481		return 0;
482
483	/* pending complex operations are too difficult to analyse */
484	if (sma->complex_count)
485		return 1;
486
487	/* we were a sleeping complex operation. Too difficult */
488	if (q->nsops > 1)
489		return 1;
490
491	curr = sma->sem_base + q->sops[0].sem_num;
492
493	/* No-one waits on this queue */
494	if (list_empty(&curr->sem_pending))
495		return 0;
496
497	/* the new semaphore value */
498	if (curr->semval) {
499		/* It is impossible that someone waits for the new value:
500		 * - q is a previously sleeping simple operation that
501		 *   altered the array. It must be a decrement, because
502		 *   simple increments never sleep.
503		 * - The value is not 0, thus wait-for-zero won't proceed.
504		 * - If there are older (higher priority) decrements
505		 *   in the queue, then they have observed the original
506		 *   semval value and couldn't proceed. The operation
507		 *   decremented to value - thus they won't proceed either.
508		 */
509		BUG_ON(q->sops[0].sem_op >= 0);
510		return 0;
511	}
512	/*
513	 * semval is 0. Check if there are wait-for-zero semops.
514	 * They must be the first entries in the per-semaphore simple queue
515	 */
516	h = list_first_entry(&curr->sem_pending, struct sem_queue, simple_list);
517	BUG_ON(h->nsops != 1);
518	BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num);
519
520	/* Yes, there is a wait-for-zero semop. Restart */
521	if (h->sops[0].sem_op == 0)
522		return 1;
523
524	/* Again - no-one is waiting for the new value. */
525	return 0;
526}
527
528
529/**
530 * update_queue(sma, semnum): Look for tasks that can be completed.
531 * @sma: semaphore array.
532 * @semnum: semaphore that was modified.
533 * @pt: list head for the tasks that must be woken up.
534 *
535 * update_queue must be called after a semaphore in a semaphore array
536 * was modified. If multiple semaphore were modified, then @semnum
537 * must be set to -1.
538 * The tasks that must be woken up are added to @pt. The return code
539 * is stored in q->pid.
540 * The function return 1 if at least one semop was completed successfully.
541 */
542static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
543{
544	struct sem_queue *q;
545	struct list_head *walk;
546	struct list_head *pending_list;
547	int offset;
548	int semop_completed = 0;
549
550	/* if there are complex operations around, then knowing the semaphore
551	 * that was modified doesn't help us. Assume that multiple semaphores
552	 * were modified.
553	 */
554	if (sma->complex_count)
555		semnum = -1;
556
557	if (semnum == -1) {
558		pending_list = &sma->sem_pending;
559		offset = offsetof(struct sem_queue, list);
560	} else {
561		pending_list = &sma->sem_base[semnum].sem_pending;
562		offset = offsetof(struct sem_queue, simple_list);
563	}
564
565again:
566	walk = pending_list->next;
567	while (walk != pending_list) {
568		int error, restart;
569
570		q = (struct sem_queue *)((char *)walk - offset);
571		walk = walk->next;
572
573		/* If we are scanning the single sop, per-semaphore list of
574		 * one semaphore and that semaphore is 0, then it is not
575		 * necessary to scan the "alter" entries: simple increments
576		 * that affect only one entry succeed immediately and cannot
577		 * be in the  per semaphore pending queue, and decrements
578		 * cannot be successful if the value is already 0.
579		 */
580		if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
581				q->alter)
582			break;
583
584		error = try_atomic_semop(sma, q->sops, q->nsops,
585					 q->undo, q->pid);
586
587		/* Does q->sleeper still need to sleep? */
588		if (error > 0)
589			continue;
590
591		unlink_queue(sma, q);
592
593		if (error) {
594			restart = 0;
595		} else {
596			semop_completed = 1;
597			restart = check_restart(sma, q);
598		}
599
600		wake_up_sem_queue_prepare(pt, q, error);
601		if (restart)
602			goto again;
603	}
604	return semop_completed;
605}
606
607/**
608 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
609 * @sma: semaphore array
610 * @sops: operations that were performed
611 * @nsops: number of operations
612 * @otime: force setting otime
613 * @pt: list head of the tasks that must be woken up.
614 *
615 * do_smart_update() does the required called to update_queue, based on the
616 * actual changes that were performed on the semaphore array.
617 * Note that the function does not do the actual wake-up: the caller is
618 * responsible for calling wake_up_sem_queue_do(@pt).
619 * It is safe to perform this call after dropping all locks.
620 */
621static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
622			int otime, struct list_head *pt)
623{
624	int i;
625
626	if (sma->complex_count || sops == NULL) {
627		if (update_queue(sma, -1, pt))
628			otime = 1;
629		goto done;
630	}
631
632	for (i = 0; i < nsops; i++) {
633		if (sops[i].sem_op > 0 ||
634			(sops[i].sem_op < 0 &&
635				sma->sem_base[sops[i].sem_num].semval == 0))
636			if (update_queue(sma, sops[i].sem_num, pt))
637				otime = 1;
638	}
639done:
640	if (otime)
641		sma->sem_otime = get_seconds();
642}
643
644
645/* The following counts are associated to each semaphore:
646 *   semncnt        number of tasks waiting on semval being nonzero
647 *   semzcnt        number of tasks waiting on semval being zero
648 * This model assumes that a task waits on exactly one semaphore.
649 * Since semaphore operations are to be performed atomically, tasks actually
650 * wait on a whole sequence of semaphores simultaneously.
651 * The counts we return here are a rough approximation, but still
652 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
653 */
654static int count_semncnt (struct sem_array * sma, ushort semnum)
655{
656	int semncnt;
657	struct sem_queue * q;
658
659	semncnt = 0;
660	list_for_each_entry(q, &sma->sem_pending, list) {
661		struct sembuf * sops = q->sops;
662		int nsops = q->nsops;
663		int i;
664		for (i = 0; i < nsops; i++)
665			if (sops[i].sem_num == semnum
666			    && (sops[i].sem_op < 0)
667			    && !(sops[i].sem_flg & IPC_NOWAIT))
668				semncnt++;
669	}
670	return semncnt;
671}
672
673static int count_semzcnt (struct sem_array * sma, ushort semnum)
674{
675	int semzcnt;
676	struct sem_queue * q;
677
678	semzcnt = 0;
679	list_for_each_entry(q, &sma->sem_pending, list) {
680		struct sembuf * sops = q->sops;
681		int nsops = q->nsops;
682		int i;
683		for (i = 0; i < nsops; i++)
684			if (sops[i].sem_num == semnum
685			    && (sops[i].sem_op == 0)
686			    && !(sops[i].sem_flg & IPC_NOWAIT))
687				semzcnt++;
688	}
689	return semzcnt;
690}
691
692/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
693 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
694 * remains locked on exit.
695 */
696static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
697{
698	struct sem_undo *un, *tu;
699	struct sem_queue *q, *tq;
700	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
701	struct list_head tasks;
702
703	/* Free the existing undo structures for this semaphore set.  */
704	assert_spin_locked(&sma->sem_perm.lock);
705	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
706		list_del(&un->list_id);
707		spin_lock(&un->ulp->lock);
708		un->semid = -1;
709		list_del_rcu(&un->list_proc);
710		spin_unlock(&un->ulp->lock);
711		kfree_rcu(un, rcu);
712	}
713
714	/* Wake up all pending processes and let them fail with EIDRM. */
715	INIT_LIST_HEAD(&tasks);
716	list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
717		unlink_queue(sma, q);
718		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
719	}
720
721	/* Remove the semaphore set from the IDR */
722	sem_rmid(ns, sma);
723	sem_unlock(sma);
724
725	wake_up_sem_queue_do(&tasks);
726	ns->used_sems -= sma->sem_nsems;
727	security_sem_free(sma);
728	ipc_rcu_putref(sma);
729}
730
731static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
732{
733	switch(version) {
734	case IPC_64:
735		return copy_to_user(buf, in, sizeof(*in));
736	case IPC_OLD:
737	    {
738		struct semid_ds out;
739
740		memset(&out, 0, sizeof(out));
741
742		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
743
744		out.sem_otime	= in->sem_otime;
745		out.sem_ctime	= in->sem_ctime;
746		out.sem_nsems	= in->sem_nsems;
747
748		return copy_to_user(buf, &out, sizeof(out));
749	    }
750	default:
751		return -EINVAL;
752	}
753}
754
755static int semctl_nolock(struct ipc_namespace *ns, int semid,
756			 int cmd, int version, union semun arg)
757{
758	int err;
759	struct sem_array *sma;
760
761	switch(cmd) {
762	case IPC_INFO:
763	case SEM_INFO:
764	{
765		struct seminfo seminfo;
766		int max_id;
767
768		err = security_sem_semctl(NULL, cmd);
769		if (err)
770			return err;
771
772		memset(&seminfo,0,sizeof(seminfo));
773		seminfo.semmni = ns->sc_semmni;
774		seminfo.semmns = ns->sc_semmns;
775		seminfo.semmsl = ns->sc_semmsl;
776		seminfo.semopm = ns->sc_semopm;
777		seminfo.semvmx = SEMVMX;
778		seminfo.semmnu = SEMMNU;
779		seminfo.semmap = SEMMAP;
780		seminfo.semume = SEMUME;
781		down_read(&sem_ids(ns).rw_mutex);
782		if (cmd == SEM_INFO) {
783			seminfo.semusz = sem_ids(ns).in_use;
784			seminfo.semaem = ns->used_sems;
785		} else {
786			seminfo.semusz = SEMUSZ;
787			seminfo.semaem = SEMAEM;
788		}
789		max_id = ipc_get_maxid(&sem_ids(ns));
790		up_read(&sem_ids(ns).rw_mutex);
791		if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
792			return -EFAULT;
793		return (max_id < 0) ? 0: max_id;
794	}
795	case IPC_STAT:
796	case SEM_STAT:
797	{
798		struct semid64_ds tbuf;
799		int id;
800
801		if (cmd == SEM_STAT) {
802			sma = sem_lock(ns, semid);
803			if (IS_ERR(sma))
804				return PTR_ERR(sma);
805			id = sma->sem_perm.id;
806		} else {
807			sma = sem_lock_check(ns, semid);
808			if (IS_ERR(sma))
809				return PTR_ERR(sma);
810			id = 0;
811		}
812
813		err = -EACCES;
814		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
815			goto out_unlock;
816
817		err = security_sem_semctl(sma, cmd);
818		if (err)
819			goto out_unlock;
820
821		memset(&tbuf, 0, sizeof(tbuf));
822
823		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
824		tbuf.sem_otime  = sma->sem_otime;
825		tbuf.sem_ctime  = sma->sem_ctime;
826		tbuf.sem_nsems  = sma->sem_nsems;
827		sem_unlock(sma);
828		if (copy_semid_to_user (arg.buf, &tbuf, version))
829			return -EFAULT;
830		return id;
831	}
832	default:
833		return -EINVAL;
834	}
835out_unlock:
836	sem_unlock(sma);
837	return err;
838}
839
840static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
841		int cmd, int version, union semun arg)
842{
843	struct sem_array *sma;
844	struct sem* curr;
845	int err;
846	ushort fast_sem_io[SEMMSL_FAST];
847	ushort* sem_io = fast_sem_io;
848	int nsems;
849	struct list_head tasks;
850
851	sma = sem_lock_check(ns, semid);
852	if (IS_ERR(sma))
853		return PTR_ERR(sma);
854
855	INIT_LIST_HEAD(&tasks);
856	nsems = sma->sem_nsems;
857
858	err = -EACCES;
859	if (ipcperms(ns, &sma->sem_perm,
860			(cmd == SETVAL || cmd == SETALL) ? S_IWUGO : S_IRUGO))
861		goto out_unlock;
862
863	err = security_sem_semctl(sma, cmd);
864	if (err)
865		goto out_unlock;
866
867	err = -EACCES;
868	switch (cmd) {
869	case GETALL:
870	{
871		ushort __user *array = arg.array;
872		int i;
873
874		if(nsems > SEMMSL_FAST) {
875			sem_getref_and_unlock(sma);
876
877			sem_io = ipc_alloc(sizeof(ushort)*nsems);
878			if(sem_io == NULL) {
879				sem_putref(sma);
880				return -ENOMEM;
881			}
882
883			sem_lock_and_putref(sma);
884			if (sma->sem_perm.deleted) {
885				sem_unlock(sma);
886				err = -EIDRM;
887				goto out_free;
888			}
889		}
890
891		for (i = 0; i < sma->sem_nsems; i++)
892			sem_io[i] = sma->sem_base[i].semval;
893		sem_unlock(sma);
894		err = 0;
895		if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
896			err = -EFAULT;
897		goto out_free;
898	}
899	case SETALL:
900	{
901		int i;
902		struct sem_undo *un;
903
904		sem_getref_and_unlock(sma);
905
906		if(nsems > SEMMSL_FAST) {
907			sem_io = ipc_alloc(sizeof(ushort)*nsems);
908			if(sem_io == NULL) {
909				sem_putref(sma);
910				return -ENOMEM;
911			}
912		}
913
914		if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
915			sem_putref(sma);
916			err = -EFAULT;
917			goto out_free;
918		}
919
920		for (i = 0; i < nsems; i++) {
921			if (sem_io[i] > SEMVMX) {
922				sem_putref(sma);
923				err = -ERANGE;
924				goto out_free;
925			}
926		}
927		sem_lock_and_putref(sma);
928		if (sma->sem_perm.deleted) {
929			sem_unlock(sma);
930			err = -EIDRM;
931			goto out_free;
932		}
933
934		for (i = 0; i < nsems; i++)
935			sma->sem_base[i].semval = sem_io[i];
936
937		assert_spin_locked(&sma->sem_perm.lock);
938		list_for_each_entry(un, &sma->list_id, list_id) {
939			for (i = 0; i < nsems; i++)
940				un->semadj[i] = 0;
941		}
942		sma->sem_ctime = get_seconds();
943		/* maybe some queued-up processes were waiting for this */
944		do_smart_update(sma, NULL, 0, 0, &tasks);
945		err = 0;
946		goto out_unlock;
947	}
948	/* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
949	}
950	err = -EINVAL;
951	if(semnum < 0 || semnum >= nsems)
952		goto out_unlock;
953
954	curr = &sma->sem_base[semnum];
955
956	switch (cmd) {
957	case GETVAL:
958		err = curr->semval;
959		goto out_unlock;
960	case GETPID:
961		err = curr->sempid;
962		goto out_unlock;
963	case GETNCNT:
964		err = count_semncnt(sma,semnum);
965		goto out_unlock;
966	case GETZCNT:
967		err = count_semzcnt(sma,semnum);
968		goto out_unlock;
969	case SETVAL:
970	{
971		int val = arg.val;
972		struct sem_undo *un;
973
974		err = -ERANGE;
975		if (val > SEMVMX || val < 0)
976			goto out_unlock;
977
978		assert_spin_locked(&sma->sem_perm.lock);
979		list_for_each_entry(un, &sma->list_id, list_id)
980			un->semadj[semnum] = 0;
981
982		curr->semval = val;
983		curr->sempid = task_tgid_vnr(current);
984		sma->sem_ctime = get_seconds();
985		/* maybe some queued-up processes were waiting for this */
986		do_smart_update(sma, NULL, 0, 0, &tasks);
987		err = 0;
988		goto out_unlock;
989	}
990	}
991out_unlock:
992	sem_unlock(sma);
993	wake_up_sem_queue_do(&tasks);
994
995out_free:
996	if(sem_io != fast_sem_io)
997		ipc_free(sem_io, sizeof(ushort)*nsems);
998	return err;
999}
1000
1001static inline unsigned long
1002copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1003{
1004	switch(version) {
1005	case IPC_64:
1006		if (copy_from_user(out, buf, sizeof(*out)))
1007			return -EFAULT;
1008		return 0;
1009	case IPC_OLD:
1010	    {
1011		struct semid_ds tbuf_old;
1012
1013		if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1014			return -EFAULT;
1015
1016		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1017		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1018		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1019
1020		return 0;
1021	    }
1022	default:
1023		return -EINVAL;
1024	}
1025}
1026
1027/*
1028 * This function handles some semctl commands which require the rw_mutex
1029 * to be held in write mode.
1030 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1031 */
1032static int semctl_down(struct ipc_namespace *ns, int semid,
1033		       int cmd, int version, union semun arg)
1034{
1035	struct sem_array *sma;
1036	int err;
1037	struct semid64_ds semid64;
1038	struct kern_ipc_perm *ipcp;
1039
1040	if(cmd == IPC_SET) {
1041		if (copy_semid_from_user(&semid64, arg.buf, version))
1042			return -EFAULT;
1043	}
1044
1045	ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd,
1046			       &semid64.sem_perm, 0);
1047	if (IS_ERR(ipcp))
1048		return PTR_ERR(ipcp);
1049
1050	sma = container_of(ipcp, struct sem_array, sem_perm);
1051
1052	err = security_sem_semctl(sma, cmd);
1053	if (err)
1054		goto out_unlock;
1055
1056	switch(cmd){
1057	case IPC_RMID:
1058		freeary(ns, ipcp);
1059		goto out_up;
1060	case IPC_SET:
1061		ipc_update_perm(&semid64.sem_perm, ipcp);
1062		sma->sem_ctime = get_seconds();
1063		break;
1064	default:
1065		err = -EINVAL;
1066	}
1067
1068out_unlock:
1069	sem_unlock(sma);
1070out_up:
1071	up_write(&sem_ids(ns).rw_mutex);
1072	return err;
1073}
1074
1075SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
1076{
1077	int err = -EINVAL;
1078	int version;
1079	struct ipc_namespace *ns;
1080
1081	if (semid < 0)
1082		return -EINVAL;
1083
1084	version = ipc_parse_version(&cmd);
1085	ns = current->nsproxy->ipc_ns;
1086
1087	switch(cmd) {
1088	case IPC_INFO:
1089	case SEM_INFO:
1090	case IPC_STAT:
1091	case SEM_STAT:
1092		err = semctl_nolock(ns, semid, cmd, version, arg);
1093		return err;
1094	case GETALL:
1095	case GETVAL:
1096	case GETPID:
1097	case GETNCNT:
1098	case GETZCNT:
1099	case SETVAL:
1100	case SETALL:
1101		err = semctl_main(ns,semid,semnum,cmd,version,arg);
1102		return err;
1103	case IPC_RMID:
1104	case IPC_SET:
1105		err = semctl_down(ns, semid, cmd, version, arg);
1106		return err;
1107	default:
1108		return -EINVAL;
1109	}
1110}
1111#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1112asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
1113{
1114	return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
1115}
1116SYSCALL_ALIAS(sys_semctl, SyS_semctl);
1117#endif
1118
1119/* If the task doesn't already have a undo_list, then allocate one
1120 * here.  We guarantee there is only one thread using this undo list,
1121 * and current is THE ONE
1122 *
1123 * If this allocation and assignment succeeds, but later
1124 * portions of this code fail, there is no need to free the sem_undo_list.
1125 * Just let it stay associated with the task, and it'll be freed later
1126 * at exit time.
1127 *
1128 * This can block, so callers must hold no locks.
1129 */
1130static inline int get_undo_list(struct sem_undo_list **undo_listp)
1131{
1132	struct sem_undo_list *undo_list;
1133
1134	undo_list = current->sysvsem.undo_list;
1135	if (!undo_list) {
1136		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1137		if (undo_list == NULL)
1138			return -ENOMEM;
1139		spin_lock_init(&undo_list->lock);
1140		atomic_set(&undo_list->refcnt, 1);
1141		INIT_LIST_HEAD(&undo_list->list_proc);
1142
1143		current->sysvsem.undo_list = undo_list;
1144	}
1145	*undo_listp = undo_list;
1146	return 0;
1147}
1148
1149static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1150{
1151	struct sem_undo *un;
1152
1153	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1154		if (un->semid == semid)
1155			return un;
1156	}
1157	return NULL;
1158}
1159
1160static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1161{
1162	struct sem_undo *un;
1163
1164  	assert_spin_locked(&ulp->lock);
1165
1166	un = __lookup_undo(ulp, semid);
1167	if (un) {
1168		list_del_rcu(&un->list_proc);
1169		list_add_rcu(&un->list_proc, &ulp->list_proc);
1170	}
1171	return un;
1172}
1173
1174/**
1175 * find_alloc_undo - Lookup (and if not present create) undo array
1176 * @ns: namespace
1177 * @semid: semaphore array id
1178 *
1179 * The function looks up (and if not present creates) the undo structure.
1180 * The size of the undo structure depends on the size of the semaphore
1181 * array, thus the alloc path is not that straightforward.
1182 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1183 * performs a rcu_read_lock().
1184 */
1185static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1186{
1187	struct sem_array *sma;
1188	struct sem_undo_list *ulp;
1189	struct sem_undo *un, *new;
1190	int nsems;
1191	int error;
1192
1193	error = get_undo_list(&ulp);
1194	if (error)
1195		return ERR_PTR(error);
1196
1197	rcu_read_lock();
1198	spin_lock(&ulp->lock);
1199	un = lookup_undo(ulp, semid);
1200	spin_unlock(&ulp->lock);
1201	if (likely(un!=NULL))
1202		goto out;
1203	rcu_read_unlock();
1204
1205	/* no undo structure around - allocate one. */
1206	/* step 1: figure out the size of the semaphore array */
1207	sma = sem_lock_check(ns, semid);
1208	if (IS_ERR(sma))
1209		return ERR_CAST(sma);
1210
1211	nsems = sma->sem_nsems;
1212	sem_getref_and_unlock(sma);
1213
1214	/* step 2: allocate new undo structure */
1215	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1216	if (!new) {
1217		sem_putref(sma);
1218		return ERR_PTR(-ENOMEM);
1219	}
1220
1221	/* step 3: Acquire the lock on semaphore array */
1222	sem_lock_and_putref(sma);
1223	if (sma->sem_perm.deleted) {
1224		sem_unlock(sma);
1225		kfree(new);
1226		un = ERR_PTR(-EIDRM);
1227		goto out;
1228	}
1229	spin_lock(&ulp->lock);
1230
1231	/*
1232	 * step 4: check for races: did someone else allocate the undo struct?
1233	 */
1234	un = lookup_undo(ulp, semid);
1235	if (un) {
1236		kfree(new);
1237		goto success;
1238	}
1239	/* step 5: initialize & link new undo structure */
1240	new->semadj = (short *) &new[1];
1241	new->ulp = ulp;
1242	new->semid = semid;
1243	assert_spin_locked(&ulp->lock);
1244	list_add_rcu(&new->list_proc, &ulp->list_proc);
1245	assert_spin_locked(&sma->sem_perm.lock);
1246	list_add(&new->list_id, &sma->list_id);
1247	un = new;
1248
1249success:
1250	spin_unlock(&ulp->lock);
1251	rcu_read_lock();
1252	sem_unlock(sma);
1253out:
1254	return un;
1255}
1256
1257
1258/**
1259 * get_queue_result - Retrieve the result code from sem_queue
1260 * @q: Pointer to queue structure
1261 *
1262 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1263 * q->status, then we must loop until the value is replaced with the final
1264 * value: This may happen if a task is woken up by an unrelated event (e.g.
1265 * signal) and in parallel the task is woken up by another task because it got
1266 * the requested semaphores.
1267 *
1268 * The function can be called with or without holding the semaphore spinlock.
1269 */
1270static int get_queue_result(struct sem_queue *q)
1271{
1272	int error;
1273
1274	error = q->status;
1275	while (unlikely(error == IN_WAKEUP)) {
1276		cpu_relax();
1277		error = q->status;
1278	}
1279
1280	return error;
1281}
1282
1283
1284SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1285		unsigned, nsops, const struct timespec __user *, timeout)
1286{
1287	int error = -EINVAL;
1288	struct sem_array *sma;
1289	struct sembuf fast_sops[SEMOPM_FAST];
1290	struct sembuf* sops = fast_sops, *sop;
1291	struct sem_undo *un;
1292	int undos = 0, alter = 0, max;
1293	struct sem_queue queue;
1294	unsigned long jiffies_left = 0;
1295	struct ipc_namespace *ns;
1296	struct list_head tasks;
1297
1298	ns = current->nsproxy->ipc_ns;
1299
1300	if (nsops < 1 || semid < 0)
1301		return -EINVAL;
1302	if (nsops > ns->sc_semopm)
1303		return -E2BIG;
1304	if(nsops > SEMOPM_FAST) {
1305		sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1306		if(sops==NULL)
1307			return -ENOMEM;
1308	}
1309	if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1310		error=-EFAULT;
1311		goto out_free;
1312	}
1313	if (timeout) {
1314		struct timespec _timeout;
1315		if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1316			error = -EFAULT;
1317			goto out_free;
1318		}
1319		if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1320			_timeout.tv_nsec >= 1000000000L) {
1321			error = -EINVAL;
1322			goto out_free;
1323		}
1324		jiffies_left = timespec_to_jiffies(&_timeout);
1325	}
1326	max = 0;
1327	for (sop = sops; sop < sops + nsops; sop++) {
1328		if (sop->sem_num >= max)
1329			max = sop->sem_num;
1330		if (sop->sem_flg & SEM_UNDO)
1331			undos = 1;
1332		if (sop->sem_op != 0)
1333			alter = 1;
1334	}
1335
1336	if (undos) {
1337		un = find_alloc_undo(ns, semid);
1338		if (IS_ERR(un)) {
1339			error = PTR_ERR(un);
1340			goto out_free;
1341		}
1342	} else
1343		un = NULL;
1344
1345	INIT_LIST_HEAD(&tasks);
1346
1347	sma = sem_lock_check(ns, semid);
1348	if (IS_ERR(sma)) {
1349		if (un)
1350			rcu_read_unlock();
1351		error = PTR_ERR(sma);
1352		goto out_free;
1353	}
1354
1355	/*
1356	 * semid identifiers are not unique - find_alloc_undo may have
1357	 * allocated an undo structure, it was invalidated by an RMID
1358	 * and now a new array with received the same id. Check and fail.
1359	 * This case can be detected checking un->semid. The existence of
1360	 * "un" itself is guaranteed by rcu.
1361	 */
1362	error = -EIDRM;
1363	if (un) {
1364		if (un->semid == -1) {
1365			rcu_read_unlock();
1366			goto out_unlock_free;
1367		} else {
1368			/*
1369			 * rcu lock can be released, "un" cannot disappear:
1370			 * - sem_lock is acquired, thus IPC_RMID is
1371			 *   impossible.
1372			 * - exit_sem is impossible, it always operates on
1373			 *   current (or a dead task).
1374			 */
1375
1376			rcu_read_unlock();
1377		}
1378	}
1379
1380	error = -EFBIG;
1381	if (max >= sma->sem_nsems)
1382		goto out_unlock_free;
1383
1384	error = -EACCES;
1385	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1386		goto out_unlock_free;
1387
1388	error = security_sem_semop(sma, sops, nsops, alter);
1389	if (error)
1390		goto out_unlock_free;
1391
1392	error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
1393	if (error <= 0) {
1394		if (alter && error == 0)
1395			do_smart_update(sma, sops, nsops, 1, &tasks);
1396
1397		goto out_unlock_free;
1398	}
1399
1400	/* We need to sleep on this operation, so we put the current
1401	 * task into the pending queue and go to sleep.
1402	 */
1403
1404	queue.sops = sops;
1405	queue.nsops = nsops;
1406	queue.undo = un;
1407	queue.pid = task_tgid_vnr(current);
1408	queue.alter = alter;
1409	if (alter)
1410		list_add_tail(&queue.list, &sma->sem_pending);
1411	else
1412		list_add(&queue.list, &sma->sem_pending);
1413
1414	if (nsops == 1) {
1415		struct sem *curr;
1416		curr = &sma->sem_base[sops->sem_num];
1417
1418		if (alter)
1419			list_add_tail(&queue.simple_list, &curr->sem_pending);
1420		else
1421			list_add(&queue.simple_list, &curr->sem_pending);
1422	} else {
1423		INIT_LIST_HEAD(&queue.simple_list);
1424		sma->complex_count++;
1425	}
1426
1427	queue.status = -EINTR;
1428	queue.sleeper = current;
1429
1430sleep_again:
1431	current->state = TASK_INTERRUPTIBLE;
1432	sem_unlock(sma);
1433
1434	if (timeout)
1435		jiffies_left = schedule_timeout(jiffies_left);
1436	else
1437		schedule();
1438
1439	error = get_queue_result(&queue);
1440
1441	if (error != -EINTR) {
1442		/* fast path: update_queue already obtained all requested
1443		 * resources.
1444		 * Perform a smp_mb(): User space could assume that semop()
1445		 * is a memory barrier: Without the mb(), the cpu could
1446		 * speculatively read in user space stale data that was
1447		 * overwritten by the previous owner of the semaphore.
1448		 */
1449		smp_mb();
1450
1451		goto out_free;
1452	}
1453
1454	sma = sem_lock(ns, semid);
1455
1456	/*
1457	 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1458	 */
1459	error = get_queue_result(&queue);
1460
1461	/*
1462	 * Array removed? If yes, leave without sem_unlock().
1463	 */
1464	if (IS_ERR(sma)) {
1465		goto out_free;
1466	}
1467
1468
1469	/*
1470	 * If queue.status != -EINTR we are woken up by another process.
1471	 * Leave without unlink_queue(), but with sem_unlock().
1472	 */
1473
1474	if (error != -EINTR) {
1475		goto out_unlock_free;
1476	}
1477
1478	/*
1479	 * If an interrupt occurred we have to clean up the queue
1480	 */
1481	if (timeout && jiffies_left == 0)
1482		error = -EAGAIN;
1483
1484	/*
1485	 * If the wakeup was spurious, just retry
1486	 */
1487	if (error == -EINTR && !signal_pending(current))
1488		goto sleep_again;
1489
1490	unlink_queue(sma, &queue);
1491
1492out_unlock_free:
1493	sem_unlock(sma);
1494
1495	wake_up_sem_queue_do(&tasks);
1496out_free:
1497	if(sops != fast_sops)
1498		kfree(sops);
1499	return error;
1500}
1501
1502SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1503		unsigned, nsops)
1504{
1505	return sys_semtimedop(semid, tsops, nsops, NULL);
1506}
1507
1508/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1509 * parent and child tasks.
1510 */
1511
1512int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1513{
1514	struct sem_undo_list *undo_list;
1515	int error;
1516
1517	if (clone_flags & CLONE_SYSVSEM) {
1518		error = get_undo_list(&undo_list);
1519		if (error)
1520			return error;
1521		atomic_inc(&undo_list->refcnt);
1522		tsk->sysvsem.undo_list = undo_list;
1523	} else
1524		tsk->sysvsem.undo_list = NULL;
1525
1526	return 0;
1527}
1528
1529/*
1530 * add semadj values to semaphores, free undo structures.
1531 * undo structures are not freed when semaphore arrays are destroyed
1532 * so some of them may be out of date.
1533 * IMPLEMENTATION NOTE: There is some confusion over whether the
1534 * set of adjustments that needs to be done should be done in an atomic
1535 * manner or not. That is, if we are attempting to decrement the semval
1536 * should we queue up and wait until we can do so legally?
1537 * The original implementation attempted to do this (queue and wait).
1538 * The current implementation does not do so. The POSIX standard
1539 * and SVID should be consulted to determine what behavior is mandated.
1540 */
1541void exit_sem(struct task_struct *tsk)
1542{
1543	struct sem_undo_list *ulp;
1544
1545	ulp = tsk->sysvsem.undo_list;
1546	if (!ulp)
1547		return;
1548	tsk->sysvsem.undo_list = NULL;
1549
1550	if (!atomic_dec_and_test(&ulp->refcnt))
1551		return;
1552
1553	for (;;) {
1554		struct sem_array *sma;
1555		struct sem_undo *un;
1556		struct list_head tasks;
1557		int semid;
1558		int i;
1559
1560		rcu_read_lock();
1561		un = list_entry_rcu(ulp->list_proc.next,
1562				    struct sem_undo, list_proc);
1563		if (&un->list_proc == &ulp->list_proc)
1564			semid = -1;
1565		 else
1566			semid = un->semid;
1567		rcu_read_unlock();
1568
1569		if (semid == -1)
1570			break;
1571
1572		sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
1573
1574		/* exit_sem raced with IPC_RMID, nothing to do */
1575		if (IS_ERR(sma))
1576			continue;
1577
1578		un = __lookup_undo(ulp, semid);
1579		if (un == NULL) {
1580			/* exit_sem raced with IPC_RMID+semget() that created
1581			 * exactly the same semid. Nothing to do.
1582			 */
1583			sem_unlock(sma);
1584			continue;
1585		}
1586
1587		/* remove un from the linked lists */
1588		assert_spin_locked(&sma->sem_perm.lock);
1589		list_del(&un->list_id);
1590
1591		spin_lock(&ulp->lock);
1592		list_del_rcu(&un->list_proc);
1593		spin_unlock(&ulp->lock);
1594
1595		/* perform adjustments registered in un */
1596		for (i = 0; i < sma->sem_nsems; i++) {
1597			struct sem * semaphore = &sma->sem_base[i];
1598			if (un->semadj[i]) {
1599				semaphore->semval += un->semadj[i];
1600				/*
1601				 * Range checks of the new semaphore value,
1602				 * not defined by sus:
1603				 * - Some unices ignore the undo entirely
1604				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
1605				 * - some cap the value (e.g. FreeBSD caps
1606				 *   at 0, but doesn't enforce SEMVMX)
1607				 *
1608				 * Linux caps the semaphore value, both at 0
1609				 * and at SEMVMX.
1610				 *
1611				 * 	Manfred <manfred@colorfullife.com>
1612				 */
1613				if (semaphore->semval < 0)
1614					semaphore->semval = 0;
1615				if (semaphore->semval > SEMVMX)
1616					semaphore->semval = SEMVMX;
1617				semaphore->sempid = task_tgid_vnr(current);
1618			}
1619		}
1620		/* maybe some queued-up processes were waiting for this */
1621		INIT_LIST_HEAD(&tasks);
1622		do_smart_update(sma, NULL, 0, 1, &tasks);
1623		sem_unlock(sma);
1624		wake_up_sem_queue_do(&tasks);
1625
1626		kfree_rcu(un, rcu);
1627	}
1628	kfree(ulp);
1629}
1630
1631#ifdef CONFIG_PROC_FS
1632static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
1633{
1634	struct sem_array *sma = it;
1635
1636	return seq_printf(s,
1637			  "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
1638			  sma->sem_perm.key,
1639			  sma->sem_perm.id,
1640			  sma->sem_perm.mode,
1641			  sma->sem_nsems,
1642			  sma->sem_perm.uid,
1643			  sma->sem_perm.gid,
1644			  sma->sem_perm.cuid,
1645			  sma->sem_perm.cgid,
1646			  sma->sem_otime,
1647			  sma->sem_ctime);
1648}
1649#endif
1650