3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
6 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
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
13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
14 * Further wakeup optimizations, documentation
15 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
22 * Pavel Emelianov <xemul@openvz.org>
24 * Implementation notes: (May 2010)
25 * This file implements System V semaphores.
27 * User space visible behavior:
28 * - FIFO ordering for semop() operations (just FIFO, not starvation
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
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.
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
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.
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>
90 #include <asm/uaccess.h>
93 /* One semaphore structure for each semaphore in the system. */
95 int semval; /* current value */
96 int sempid; /* pid of last operation */
97 spinlock_t lock; /* spinlock for fine-grained semtimedop */
98 struct list_head pending_alter; /* pending single-sop operations */
99 /* that alter the semaphore */
100 struct list_head pending_const; /* pending single-sop operations */
101 /* that do not alter the semaphore*/
102 time_t sem_otime; /* candidate for sem_otime */
103 } ____cacheline_aligned_in_smp;
105 /* One queue for each sleeping process in the system. */
107 struct list_head list; /* queue of pending operations */
108 struct task_struct *sleeper; /* this process */
109 struct sem_undo *undo; /* undo structure */
110 int pid; /* process id of requesting process */
111 int status; /* completion status of operation */
112 struct sembuf *sops; /* array of pending operations */
113 int nsops; /* number of operations */
114 int alter; /* does *sops alter the array? */
117 /* Each task has a list of undo requests. They are executed automatically
118 * when the process exits.
121 struct list_head list_proc; /* per-process list: *
122 * all undos from one process
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 */
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.
136 struct sem_undo_list {
139 struct list_head list_proc;
143 #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
145 #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
147 static int newary(struct ipc_namespace *, struct ipc_params *);
148 static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
149 #ifdef CONFIG_PROC_FS
150 static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
153 #define SEMMSL_FAST 256 /* 512 bytes on stack */
154 #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
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.
164 * sem_array.sem_base[i].pending_{const,alter}:
165 * global or semaphore sem_lock() for read/write
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]
173 void sem_init_ns(struct ipc_namespace *ns)
175 ns->sc_semmsl = SEMMSL;
176 ns->sc_semmns = SEMMNS;
177 ns->sc_semopm = SEMOPM;
178 ns->sc_semmni = SEMMNI;
180 ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
184 void sem_exit_ns(struct ipc_namespace *ns)
186 free_ipcs(ns, &sem_ids(ns), freeary);
187 idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
191 void __init sem_init (void)
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);
200 * unmerge_queues - unmerge queues, if possible.
201 * @sma: semaphore array
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.
206 static void unmerge_queues(struct sem_array *sma)
208 struct sem_queue *q, *tq;
210 /* complex operations still around? */
211 if (sma->complex_count)
214 * We will switch back to simple mode.
215 * Move all pending operation back into the per-semaphore
218 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
220 curr = &sma->sem_base[q->sops[0].sem_num];
222 list_add_tail(&q->list, &curr->pending_alter);
224 INIT_LIST_HEAD(&sma->pending_alter);
228 * merge_queues - Merge single semop queues into global queue
229 * @sma: semaphore array
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.
236 static void merge_queues(struct sem_array *sma)
239 for (i = 0; i < sma->sem_nsems; i++) {
240 struct sem *sem = sma->sem_base + i;
242 list_splice_init(&sem->pending_alter, &sma->pending_alter);
246 static void sem_rcu_free(struct rcu_head *head)
248 struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
249 struct sem_array *sma = ipc_rcu_to_struct(p);
251 security_sem_free(sma);
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.
262 static void sem_wait_array(struct sem_array *sma)
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.
274 for (i = 0; i < sma->sem_nsems; i++) {
275 sem = sma->sem_base + i;
276 spin_unlock_wait(&sem->lock);
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.
287 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
293 /* Complex operation - acquire a full lock */
294 ipc_lock_object(&sma->sem_perm);
296 /* And wait until all simple ops that are processed
297 * right now have dropped their locks.
304 * Only one semaphore affected - try to optimize locking.
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.
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.
318 sem = sma->sem_base + sops->sem_num;
320 if (sma->complex_count == 0) {
322 * It appears that no complex operation is around.
323 * Acquire the per-semaphore lock.
325 spin_lock(&sem->lock);
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 */
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.
336 if (sma->complex_count == 0) {
337 /* fast path successful! */
338 return sops->sem_num;
341 spin_unlock(&sem->lock);
344 /* slow path: acquire the full lock */
345 ipc_lock_object(&sma->sem_perm);
347 if (sma->complex_count == 0) {
349 * There is no complex operation, thus we can switch
350 * back to the fast path.
352 spin_lock(&sem->lock);
353 ipc_unlock_object(&sma->sem_perm);
354 return sops->sem_num;
356 /* Not a false alarm, thus complete the sequence for a
364 static inline void sem_unlock(struct sem_array *sma, int locknum)
368 ipc_unlock_object(&sma->sem_perm);
370 struct sem *sem = sma->sem_base + locknum;
371 spin_unlock(&sem->lock);
376 * sem_lock_(check_) routines are called in the paths where the rwsem
379 * The caller holds the RCU read lock.
381 static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
382 int id, struct sembuf *sops, int nsops, int *locknum)
384 struct kern_ipc_perm *ipcp;
385 struct sem_array *sma;
387 ipcp = ipc_obtain_object(&sem_ids(ns), id);
389 return ERR_CAST(ipcp);
391 sma = container_of(ipcp, struct sem_array, sem_perm);
392 *locknum = sem_lock(sma, sops, nsops);
394 /* ipc_rmid() may have already freed the ID while sem_lock
395 * was spinning: verify that the structure is still valid
398 return container_of(ipcp, struct sem_array, sem_perm);
400 sem_unlock(sma, *locknum);
401 return ERR_PTR(-EINVAL);
404 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
406 struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
409 return ERR_CAST(ipcp);
411 return container_of(ipcp, struct sem_array, sem_perm);
414 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
417 struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
420 return ERR_CAST(ipcp);
422 return container_of(ipcp, struct sem_array, sem_perm);
425 static inline void sem_lock_and_putref(struct sem_array *sma)
427 sem_lock(sma, NULL, -1);
428 ipc_rcu_putref(sma, ipc_rcu_free);
431 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
433 ipc_rmid(&sem_ids(ns), &s->sem_perm);
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.
454 * The two-stage algorithm is necessary to protect against the following
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).
471 * newary - Create a new semaphore set
473 * @params: ptr to the structure that contains key, semflg and nsems
475 * Called with sem_ids.rwsem held (as a writer)
478 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
482 struct sem_array *sma;
484 key_t key = params->key;
485 int nsems = params->u.nsems;
486 int semflg = params->flg;
491 if (ns->used_sems + nsems > ns->sc_semmns)
494 size = sizeof (*sma) + nsems * sizeof (struct sem);
495 sma = ipc_rcu_alloc(size);
499 memset (sma, 0, size);
501 sma->sem_perm.mode = (semflg & S_IRWXUGO);
502 sma->sem_perm.key = key;
504 sma->sem_perm.security = NULL;
505 retval = security_sem_alloc(sma);
507 ipc_rcu_putref(sma, ipc_rcu_free);
511 id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
513 ipc_rcu_putref(sma, sem_rcu_free);
516 ns->used_sems += nsems;
518 sma->sem_base = (struct sem *) &sma[1];
520 for (i = 0; i < nsems; i++) {
521 INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
522 INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
523 spin_lock_init(&sma->sem_base[i].lock);
526 sma->complex_count = 0;
527 INIT_LIST_HEAD(&sma->pending_alter);
528 INIT_LIST_HEAD(&sma->pending_const);
529 INIT_LIST_HEAD(&sma->list_id);
530 sma->sem_nsems = nsems;
531 sma->sem_ctime = get_seconds();
535 return sma->sem_perm.id;
540 * Called with sem_ids.rwsem and ipcp locked.
542 static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
544 struct sem_array *sma;
546 sma = container_of(ipcp, struct sem_array, sem_perm);
547 return security_sem_associate(sma, semflg);
551 * Called with sem_ids.rwsem and ipcp locked.
553 static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
554 struct ipc_params *params)
556 struct sem_array *sma;
558 sma = container_of(ipcp, struct sem_array, sem_perm);
559 if (params->u.nsems > sma->sem_nsems)
565 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
567 struct ipc_namespace *ns;
568 struct ipc_ops sem_ops;
569 struct ipc_params sem_params;
571 ns = current->nsproxy->ipc_ns;
573 if (nsems < 0 || nsems > ns->sc_semmsl)
576 sem_ops.getnew = newary;
577 sem_ops.associate = sem_security;
578 sem_ops.more_checks = sem_more_checks;
580 sem_params.key = key;
581 sem_params.flg = semflg;
582 sem_params.u.nsems = nsems;
584 return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
587 /** perform_atomic_semop - Perform (if possible) a semaphore operation
588 * @sma: semaphore array
589 * @sops: array with operations that should be checked
590 * @nsems: number of sops
592 * @pid: pid that did the change
594 * Returns 0 if the operation was possible.
595 * Returns 1 if the operation is impossible, the caller must sleep.
596 * Negative values are error codes.
599 static int perform_atomic_semop(struct sem_array *sma, struct sembuf *sops,
600 int nsops, struct sem_undo *un, int pid)
606 for (sop = sops; sop < sops + nsops; sop++) {
607 curr = sma->sem_base + sop->sem_num;
608 sem_op = sop->sem_op;
609 result = curr->semval;
611 if (!sem_op && result)
619 if (sop->sem_flg & SEM_UNDO) {
620 int undo = un->semadj[sop->sem_num] - sem_op;
622 * Exceeding the undo range is an error.
624 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
627 curr->semval = result;
631 while (sop >= sops) {
632 sma->sem_base[sop->sem_num].sempid = pid;
633 if (sop->sem_flg & SEM_UNDO)
634 un->semadj[sop->sem_num] -= sop->sem_op;
645 if (sop->sem_flg & IPC_NOWAIT)
652 while (sop >= sops) {
653 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
660 /** wake_up_sem_queue_prepare(q, error): Prepare wake-up
661 * @q: queue entry that must be signaled
662 * @error: Error value for the signal
664 * Prepare the wake-up of the queue entry q.
666 static void wake_up_sem_queue_prepare(struct list_head *pt,
667 struct sem_queue *q, int error)
669 if (list_empty(pt)) {
671 * Hold preempt off so that we don't get preempted and have the
672 * wakee busy-wait until we're scheduled back on.
676 q->status = IN_WAKEUP;
679 list_add_tail(&q->list, pt);
683 * wake_up_sem_queue_do(pt) - do the actual wake-up
684 * @pt: list of tasks to be woken up
686 * Do the actual wake-up.
687 * The function is called without any locks held, thus the semaphore array
688 * could be destroyed already and the tasks can disappear as soon as the
689 * status is set to the actual return code.
691 static void wake_up_sem_queue_do(struct list_head *pt)
693 struct sem_queue *q, *t;
696 did_something = !list_empty(pt);
697 list_for_each_entry_safe(q, t, pt, list) {
698 wake_up_process(q->sleeper);
699 /* q can disappear immediately after writing q->status. */
707 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
711 sma->complex_count--;
714 /** check_restart(sma, q)
715 * @sma: semaphore array
716 * @q: the operation that just completed
718 * update_queue is O(N^2) when it restarts scanning the whole queue of
719 * waiting operations. Therefore this function checks if the restart is
720 * really necessary. It is called after a previously waiting operation
721 * modified the array.
722 * Note that wait-for-zero operations are handled without restart.
724 static int check_restart(struct sem_array *sma, struct sem_queue *q)
726 /* pending complex alter operations are too difficult to analyse */
727 if (!list_empty(&sma->pending_alter))
730 /* we were a sleeping complex operation. Too difficult */
734 /* It is impossible that someone waits for the new value:
735 * - complex operations always restart.
736 * - wait-for-zero are handled seperately.
737 * - q is a previously sleeping simple operation that
738 * altered the array. It must be a decrement, because
739 * simple increments never sleep.
740 * - If there are older (higher priority) decrements
741 * in the queue, then they have observed the original
742 * semval value and couldn't proceed. The operation
743 * decremented to value - thus they won't proceed either.
749 * wake_const_ops(sma, semnum, pt) - Wake up non-alter tasks
750 * @sma: semaphore array.
751 * @semnum: semaphore that was modified.
752 * @pt: list head for the tasks that must be woken up.
754 * wake_const_ops must be called after a semaphore in a semaphore array
755 * was set to 0. If complex const operations are pending, wake_const_ops must
756 * be called with semnum = -1, as well as with the number of each modified
758 * The tasks that must be woken up are added to @pt. The return code
759 * is stored in q->pid.
760 * The function returns 1 if at least one operation was completed successfully.
762 static int wake_const_ops(struct sem_array *sma, int semnum,
763 struct list_head *pt)
766 struct list_head *walk;
767 struct list_head *pending_list;
768 int semop_completed = 0;
771 pending_list = &sma->pending_const;
773 pending_list = &sma->sem_base[semnum].pending_const;
775 walk = pending_list->next;
776 while (walk != pending_list) {
779 q = container_of(walk, struct sem_queue, list);
782 error = perform_atomic_semop(sma, q->sops, q->nsops,
786 /* operation completed, remove from queue & wakeup */
788 unlink_queue(sma, q);
790 wake_up_sem_queue_prepare(pt, q, error);
795 return semop_completed;
799 * do_smart_wakeup_zero(sma, sops, nsops, pt) - wakeup all wait for zero tasks
800 * @sma: semaphore array
801 * @sops: operations that were performed
802 * @nsops: number of operations
803 * @pt: list head of the tasks that must be woken up.
805 * do_smart_wakeup_zero() checks all required queue for wait-for-zero
806 * operations, based on the actual changes that were performed on the
808 * The function returns 1 if at least one operation was completed successfully.
810 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
811 int nsops, struct list_head *pt)
814 int semop_completed = 0;
817 /* first: the per-semaphore queues, if known */
819 for (i = 0; i < nsops; i++) {
820 int num = sops[i].sem_num;
822 if (sma->sem_base[num].semval == 0) {
824 semop_completed |= wake_const_ops(sma, num, pt);
829 * No sops means modified semaphores not known.
830 * Assume all were changed.
832 for (i = 0; i < sma->sem_nsems; i++) {
833 if (sma->sem_base[i].semval == 0) {
835 semop_completed |= wake_const_ops(sma, i, pt);
840 * If one of the modified semaphores got 0,
841 * then check the global queue, too.
844 semop_completed |= wake_const_ops(sma, -1, pt);
846 return semop_completed;
851 * update_queue(sma, semnum): Look for tasks that can be completed.
852 * @sma: semaphore array.
853 * @semnum: semaphore that was modified.
854 * @pt: list head for the tasks that must be woken up.
856 * update_queue must be called after a semaphore in a semaphore array
857 * was modified. If multiple semaphores were modified, update_queue must
858 * be called with semnum = -1, as well as with the number of each modified
860 * The tasks that must be woken up are added to @pt. The return code
861 * is stored in q->pid.
862 * The function internally checks if const operations can now succeed.
864 * The function return 1 if at least one semop was completed successfully.
866 static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
869 struct list_head *walk;
870 struct list_head *pending_list;
871 int semop_completed = 0;
874 pending_list = &sma->pending_alter;
876 pending_list = &sma->sem_base[semnum].pending_alter;
879 walk = pending_list->next;
880 while (walk != pending_list) {
883 q = container_of(walk, struct sem_queue, list);
886 /* If we are scanning the single sop, per-semaphore list of
887 * one semaphore and that semaphore is 0, then it is not
888 * necessary to scan further: simple increments
889 * that affect only one entry succeed immediately and cannot
890 * be in the per semaphore pending queue, and decrements
891 * cannot be successful if the value is already 0.
893 if (semnum != -1 && sma->sem_base[semnum].semval == 0)
896 error = perform_atomic_semop(sma, q->sops, q->nsops,
899 /* Does q->sleeper still need to sleep? */
903 unlink_queue(sma, q);
909 do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
910 restart = check_restart(sma, q);
913 wake_up_sem_queue_prepare(pt, q, error);
917 return semop_completed;
921 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
922 * @sma: semaphore array
923 * @sops: operations that were performed
924 * @nsops: number of operations
925 * @otime: force setting otime
926 * @pt: list head of the tasks that must be woken up.
928 * do_smart_update() does the required calls to update_queue and wakeup_zero,
929 * based on the actual changes that were performed on the semaphore array.
930 * Note that the function does not do the actual wake-up: the caller is
931 * responsible for calling wake_up_sem_queue_do(@pt).
932 * It is safe to perform this call after dropping all locks.
934 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
935 int otime, struct list_head *pt)
939 otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
941 if (!list_empty(&sma->pending_alter)) {
942 /* semaphore array uses the global queue - just process it. */
943 otime |= update_queue(sma, -1, pt);
947 * No sops, thus the modified semaphores are not
950 for (i = 0; i < sma->sem_nsems; i++)
951 otime |= update_queue(sma, i, pt);
954 * Check the semaphores that were increased:
955 * - No complex ops, thus all sleeping ops are
957 * - if we decreased the value, then any sleeping
958 * semaphore ops wont be able to run: If the
959 * previous value was too small, then the new
960 * value will be too small, too.
962 for (i = 0; i < nsops; i++) {
963 if (sops[i].sem_op > 0) {
964 otime |= update_queue(sma,
965 sops[i].sem_num, pt);
972 sma->sem_base[0].sem_otime = get_seconds();
974 sma->sem_base[sops[0].sem_num].sem_otime =
981 /* The following counts are associated to each semaphore:
982 * semncnt number of tasks waiting on semval being nonzero
983 * semzcnt number of tasks waiting on semval being zero
984 * This model assumes that a task waits on exactly one semaphore.
985 * Since semaphore operations are to be performed atomically, tasks actually
986 * wait on a whole sequence of semaphores simultaneously.
987 * The counts we return here are a rough approximation, but still
988 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
990 static int count_semncnt (struct sem_array * sma, ushort semnum)
993 struct sem_queue * q;
996 list_for_each_entry(q, &sma->sem_base[semnum].pending_alter, list) {
997 struct sembuf * sops = q->sops;
998 BUG_ON(sops->sem_num != semnum);
999 if ((sops->sem_op < 0) && !(sops->sem_flg & IPC_NOWAIT))
1003 list_for_each_entry(q, &sma->pending_alter, list) {
1004 struct sembuf * sops = q->sops;
1005 int nsops = q->nsops;
1007 for (i = 0; i < nsops; i++)
1008 if (sops[i].sem_num == semnum
1009 && (sops[i].sem_op < 0)
1010 && !(sops[i].sem_flg & IPC_NOWAIT))
1016 static int count_semzcnt (struct sem_array * sma, ushort semnum)
1019 struct sem_queue * q;
1022 list_for_each_entry(q, &sma->sem_base[semnum].pending_const, list) {
1023 struct sembuf * sops = q->sops;
1024 BUG_ON(sops->sem_num != semnum);
1025 if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
1029 list_for_each_entry(q, &sma->pending_const, list) {
1030 struct sembuf * sops = q->sops;
1031 int nsops = q->nsops;
1033 for (i = 0; i < nsops; i++)
1034 if (sops[i].sem_num == semnum
1035 && (sops[i].sem_op == 0)
1036 && !(sops[i].sem_flg & IPC_NOWAIT))
1042 /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1043 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1044 * remains locked on exit.
1046 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1048 struct sem_undo *un, *tu;
1049 struct sem_queue *q, *tq;
1050 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1051 struct list_head tasks;
1054 /* Free the existing undo structures for this semaphore set. */
1055 ipc_assert_locked_object(&sma->sem_perm);
1056 list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1057 list_del(&un->list_id);
1058 spin_lock(&un->ulp->lock);
1060 list_del_rcu(&un->list_proc);
1061 spin_unlock(&un->ulp->lock);
1065 /* Wake up all pending processes and let them fail with EIDRM. */
1066 INIT_LIST_HEAD(&tasks);
1067 list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1068 unlink_queue(sma, q);
1069 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1072 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1073 unlink_queue(sma, q);
1074 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1076 for (i = 0; i < sma->sem_nsems; i++) {
1077 struct sem *sem = sma->sem_base + i;
1078 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1079 unlink_queue(sma, q);
1080 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1082 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1083 unlink_queue(sma, q);
1084 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1088 /* Remove the semaphore set from the IDR */
1090 sem_unlock(sma, -1);
1093 wake_up_sem_queue_do(&tasks);
1094 ns->used_sems -= sma->sem_nsems;
1095 ipc_rcu_putref(sma, sem_rcu_free);
1098 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1102 return copy_to_user(buf, in, sizeof(*in));
1105 struct semid_ds out;
1107 memset(&out, 0, sizeof(out));
1109 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1111 out.sem_otime = in->sem_otime;
1112 out.sem_ctime = in->sem_ctime;
1113 out.sem_nsems = in->sem_nsems;
1115 return copy_to_user(buf, &out, sizeof(out));
1122 static time_t get_semotime(struct sem_array *sma)
1127 res = sma->sem_base[0].sem_otime;
1128 for (i = 1; i < sma->sem_nsems; i++) {
1129 time_t to = sma->sem_base[i].sem_otime;
1137 static int semctl_nolock(struct ipc_namespace *ns, int semid,
1138 int cmd, int version, void __user *p)
1141 struct sem_array *sma;
1147 struct seminfo seminfo;
1150 err = security_sem_semctl(NULL, cmd);
1154 memset(&seminfo,0,sizeof(seminfo));
1155 seminfo.semmni = ns->sc_semmni;
1156 seminfo.semmns = ns->sc_semmns;
1157 seminfo.semmsl = ns->sc_semmsl;
1158 seminfo.semopm = ns->sc_semopm;
1159 seminfo.semvmx = SEMVMX;
1160 seminfo.semmnu = SEMMNU;
1161 seminfo.semmap = SEMMAP;
1162 seminfo.semume = SEMUME;
1163 down_read(&sem_ids(ns).rwsem);
1164 if (cmd == SEM_INFO) {
1165 seminfo.semusz = sem_ids(ns).in_use;
1166 seminfo.semaem = ns->used_sems;
1168 seminfo.semusz = SEMUSZ;
1169 seminfo.semaem = SEMAEM;
1171 max_id = ipc_get_maxid(&sem_ids(ns));
1172 up_read(&sem_ids(ns).rwsem);
1173 if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1175 return (max_id < 0) ? 0: max_id;
1180 struct semid64_ds tbuf;
1183 memset(&tbuf, 0, sizeof(tbuf));
1186 if (cmd == SEM_STAT) {
1187 sma = sem_obtain_object(ns, semid);
1192 id = sma->sem_perm.id;
1194 sma = sem_obtain_object_check(ns, semid);
1202 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1205 err = security_sem_semctl(sma, cmd);
1209 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1210 tbuf.sem_otime = get_semotime(sma);
1211 tbuf.sem_ctime = sma->sem_ctime;
1212 tbuf.sem_nsems = sma->sem_nsems;
1214 if (copy_semid_to_user(p, &tbuf, version))
1226 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1229 struct sem_undo *un;
1230 struct sem_array *sma;
1233 struct list_head tasks;
1235 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1236 /* big-endian 64bit */
1239 /* 32bit or little-endian 64bit */
1243 if (val > SEMVMX || val < 0)
1246 INIT_LIST_HEAD(&tasks);
1249 sma = sem_obtain_object_check(ns, semid);
1252 return PTR_ERR(sma);
1255 if (semnum < 0 || semnum >= sma->sem_nsems) {
1261 if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1266 err = security_sem_semctl(sma, SETVAL);
1272 sem_lock(sma, NULL, -1);
1274 curr = &sma->sem_base[semnum];
1276 ipc_assert_locked_object(&sma->sem_perm);
1277 list_for_each_entry(un, &sma->list_id, list_id)
1278 un->semadj[semnum] = 0;
1281 curr->sempid = task_tgid_vnr(current);
1282 sma->sem_ctime = get_seconds();
1283 /* maybe some queued-up processes were waiting for this */
1284 do_smart_update(sma, NULL, 0, 0, &tasks);
1285 sem_unlock(sma, -1);
1287 wake_up_sem_queue_do(&tasks);
1291 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1292 int cmd, void __user *p)
1294 struct sem_array *sma;
1297 ushort fast_sem_io[SEMMSL_FAST];
1298 ushort* sem_io = fast_sem_io;
1299 struct list_head tasks;
1301 INIT_LIST_HEAD(&tasks);
1304 sma = sem_obtain_object_check(ns, semid);
1307 return PTR_ERR(sma);
1310 nsems = sma->sem_nsems;
1313 if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1314 goto out_rcu_wakeup;
1316 err = security_sem_semctl(sma, cmd);
1318 goto out_rcu_wakeup;
1324 ushort __user *array = p;
1327 sem_lock(sma, NULL, -1);
1328 if(nsems > SEMMSL_FAST) {
1329 if (!ipc_rcu_getref(sma)) {
1330 sem_unlock(sma, -1);
1335 sem_unlock(sma, -1);
1337 sem_io = ipc_alloc(sizeof(ushort)*nsems);
1338 if(sem_io == NULL) {
1339 ipc_rcu_putref(sma, ipc_rcu_free);
1344 sem_lock_and_putref(sma);
1345 if (sma->sem_perm.deleted) {
1346 sem_unlock(sma, -1);
1352 for (i = 0; i < sma->sem_nsems; i++)
1353 sem_io[i] = sma->sem_base[i].semval;
1354 sem_unlock(sma, -1);
1357 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1364 struct sem_undo *un;
1366 if (!ipc_rcu_getref(sma)) {
1372 if(nsems > SEMMSL_FAST) {
1373 sem_io = ipc_alloc(sizeof(ushort)*nsems);
1374 if(sem_io == NULL) {
1375 ipc_rcu_putref(sma, ipc_rcu_free);
1380 if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) {
1381 ipc_rcu_putref(sma, ipc_rcu_free);
1386 for (i = 0; i < nsems; i++) {
1387 if (sem_io[i] > SEMVMX) {
1388 ipc_rcu_putref(sma, ipc_rcu_free);
1394 sem_lock_and_putref(sma);
1395 if (sma->sem_perm.deleted) {
1396 sem_unlock(sma, -1);
1402 for (i = 0; i < nsems; i++)
1403 sma->sem_base[i].semval = sem_io[i];
1405 ipc_assert_locked_object(&sma->sem_perm);
1406 list_for_each_entry(un, &sma->list_id, list_id) {
1407 for (i = 0; i < nsems; i++)
1410 sma->sem_ctime = get_seconds();
1411 /* maybe some queued-up processes were waiting for this */
1412 do_smart_update(sma, NULL, 0, 0, &tasks);
1416 /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1419 if (semnum < 0 || semnum >= nsems)
1420 goto out_rcu_wakeup;
1422 sem_lock(sma, NULL, -1);
1423 curr = &sma->sem_base[semnum];
1433 err = count_semncnt(sma,semnum);
1436 err = count_semzcnt(sma,semnum);
1441 sem_unlock(sma, -1);
1444 wake_up_sem_queue_do(&tasks);
1446 if(sem_io != fast_sem_io)
1447 ipc_free(sem_io, sizeof(ushort)*nsems);
1451 static inline unsigned long
1452 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1456 if (copy_from_user(out, buf, sizeof(*out)))
1461 struct semid_ds tbuf_old;
1463 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1466 out->sem_perm.uid = tbuf_old.sem_perm.uid;
1467 out->sem_perm.gid = tbuf_old.sem_perm.gid;
1468 out->sem_perm.mode = tbuf_old.sem_perm.mode;
1478 * This function handles some semctl commands which require the rwsem
1479 * to be held in write mode.
1480 * NOTE: no locks must be held, the rwsem is taken inside this function.
1482 static int semctl_down(struct ipc_namespace *ns, int semid,
1483 int cmd, int version, void __user *p)
1485 struct sem_array *sma;
1487 struct semid64_ds semid64;
1488 struct kern_ipc_perm *ipcp;
1490 if(cmd == IPC_SET) {
1491 if (copy_semid_from_user(&semid64, p, version))
1495 down_write(&sem_ids(ns).rwsem);
1498 ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1499 &semid64.sem_perm, 0);
1501 err = PTR_ERR(ipcp);
1505 sma = container_of(ipcp, struct sem_array, sem_perm);
1507 err = security_sem_semctl(sma, cmd);
1513 sem_lock(sma, NULL, -1);
1514 /* freeary unlocks the ipc object and rcu */
1518 sem_lock(sma, NULL, -1);
1519 err = ipc_update_perm(&semid64.sem_perm, ipcp);
1522 sma->sem_ctime = get_seconds();
1530 sem_unlock(sma, -1);
1534 up_write(&sem_ids(ns).rwsem);
1538 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1541 struct ipc_namespace *ns;
1542 void __user *p = (void __user *)arg;
1547 version = ipc_parse_version(&cmd);
1548 ns = current->nsproxy->ipc_ns;
1555 return semctl_nolock(ns, semid, cmd, version, p);
1562 return semctl_main(ns, semid, semnum, cmd, p);
1564 return semctl_setval(ns, semid, semnum, arg);
1567 return semctl_down(ns, semid, cmd, version, p);
1573 /* If the task doesn't already have a undo_list, then allocate one
1574 * here. We guarantee there is only one thread using this undo list,
1575 * and current is THE ONE
1577 * If this allocation and assignment succeeds, but later
1578 * portions of this code fail, there is no need to free the sem_undo_list.
1579 * Just let it stay associated with the task, and it'll be freed later
1582 * This can block, so callers must hold no locks.
1584 static inline int get_undo_list(struct sem_undo_list **undo_listp)
1586 struct sem_undo_list *undo_list;
1588 undo_list = current->sysvsem.undo_list;
1590 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1591 if (undo_list == NULL)
1593 spin_lock_init(&undo_list->lock);
1594 atomic_set(&undo_list->refcnt, 1);
1595 INIT_LIST_HEAD(&undo_list->list_proc);
1597 current->sysvsem.undo_list = undo_list;
1599 *undo_listp = undo_list;
1603 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1605 struct sem_undo *un;
1607 list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1608 if (un->semid == semid)
1614 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1616 struct sem_undo *un;
1618 assert_spin_locked(&ulp->lock);
1620 un = __lookup_undo(ulp, semid);
1622 list_del_rcu(&un->list_proc);
1623 list_add_rcu(&un->list_proc, &ulp->list_proc);
1629 * find_alloc_undo - Lookup (and if not present create) undo array
1631 * @semid: semaphore array id
1633 * The function looks up (and if not present creates) the undo structure.
1634 * The size of the undo structure depends on the size of the semaphore
1635 * array, thus the alloc path is not that straightforward.
1636 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1637 * performs a rcu_read_lock().
1639 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1641 struct sem_array *sma;
1642 struct sem_undo_list *ulp;
1643 struct sem_undo *un, *new;
1646 error = get_undo_list(&ulp);
1648 return ERR_PTR(error);
1651 spin_lock(&ulp->lock);
1652 un = lookup_undo(ulp, semid);
1653 spin_unlock(&ulp->lock);
1654 if (likely(un!=NULL))
1657 /* no undo structure around - allocate one. */
1658 /* step 1: figure out the size of the semaphore array */
1659 sma = sem_obtain_object_check(ns, semid);
1662 return ERR_CAST(sma);
1665 nsems = sma->sem_nsems;
1666 if (!ipc_rcu_getref(sma)) {
1668 un = ERR_PTR(-EIDRM);
1673 /* step 2: allocate new undo structure */
1674 new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1676 ipc_rcu_putref(sma, ipc_rcu_free);
1677 return ERR_PTR(-ENOMEM);
1680 /* step 3: Acquire the lock on semaphore array */
1682 sem_lock_and_putref(sma);
1683 if (sma->sem_perm.deleted) {
1684 sem_unlock(sma, -1);
1687 un = ERR_PTR(-EIDRM);
1690 spin_lock(&ulp->lock);
1693 * step 4: check for races: did someone else allocate the undo struct?
1695 un = lookup_undo(ulp, semid);
1700 /* step 5: initialize & link new undo structure */
1701 new->semadj = (short *) &new[1];
1704 assert_spin_locked(&ulp->lock);
1705 list_add_rcu(&new->list_proc, &ulp->list_proc);
1706 ipc_assert_locked_object(&sma->sem_perm);
1707 list_add(&new->list_id, &sma->list_id);
1711 spin_unlock(&ulp->lock);
1712 sem_unlock(sma, -1);
1719 * get_queue_result - Retrieve the result code from sem_queue
1720 * @q: Pointer to queue structure
1722 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1723 * q->status, then we must loop until the value is replaced with the final
1724 * value: This may happen if a task is woken up by an unrelated event (e.g.
1725 * signal) and in parallel the task is woken up by another task because it got
1726 * the requested semaphores.
1728 * The function can be called with or without holding the semaphore spinlock.
1730 static int get_queue_result(struct sem_queue *q)
1735 while (unlikely(error == IN_WAKEUP)) {
1743 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1744 unsigned, nsops, const struct timespec __user *, timeout)
1746 int error = -EINVAL;
1747 struct sem_array *sma;
1748 struct sembuf fast_sops[SEMOPM_FAST];
1749 struct sembuf* sops = fast_sops, *sop;
1750 struct sem_undo *un;
1751 int undos = 0, alter = 0, max, locknum;
1752 struct sem_queue queue;
1753 unsigned long jiffies_left = 0;
1754 struct ipc_namespace *ns;
1755 struct list_head tasks;
1757 ns = current->nsproxy->ipc_ns;
1759 if (nsops < 1 || semid < 0)
1761 if (nsops > ns->sc_semopm)
1763 if(nsops > SEMOPM_FAST) {
1764 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1768 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1773 struct timespec _timeout;
1774 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1778 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1779 _timeout.tv_nsec >= 1000000000L) {
1783 jiffies_left = timespec_to_jiffies(&_timeout);
1786 for (sop = sops; sop < sops + nsops; sop++) {
1787 if (sop->sem_num >= max)
1789 if (sop->sem_flg & SEM_UNDO)
1791 if (sop->sem_op != 0)
1795 INIT_LIST_HEAD(&tasks);
1798 /* On success, find_alloc_undo takes the rcu_read_lock */
1799 un = find_alloc_undo(ns, semid);
1801 error = PTR_ERR(un);
1809 sma = sem_obtain_object_check(ns, semid);
1812 error = PTR_ERR(sma);
1817 if (max >= sma->sem_nsems)
1818 goto out_rcu_wakeup;
1821 if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1822 goto out_rcu_wakeup;
1824 error = security_sem_semop(sma, sops, nsops, alter);
1826 goto out_rcu_wakeup;
1829 * semid identifiers are not unique - find_alloc_undo may have
1830 * allocated an undo structure, it was invalidated by an RMID
1831 * and now a new array with received the same id. Check and fail.
1832 * This case can be detected checking un->semid. The existence of
1833 * "un" itself is guaranteed by rcu.
1836 locknum = sem_lock(sma, sops, nsops);
1837 if (un && un->semid == -1)
1838 goto out_unlock_free;
1840 error = perform_atomic_semop(sma, sops, nsops, un,
1841 task_tgid_vnr(current));
1843 if (alter && error == 0)
1844 do_smart_update(sma, sops, nsops, 1, &tasks);
1846 goto out_unlock_free;
1849 /* We need to sleep on this operation, so we put the current
1850 * task into the pending queue and go to sleep.
1854 queue.nsops = nsops;
1856 queue.pid = task_tgid_vnr(current);
1857 queue.alter = alter;
1861 curr = &sma->sem_base[sops->sem_num];
1864 if (sma->complex_count) {
1865 list_add_tail(&queue.list,
1866 &sma->pending_alter);
1869 list_add_tail(&queue.list,
1870 &curr->pending_alter);
1873 list_add_tail(&queue.list, &curr->pending_const);
1876 if (!sma->complex_count)
1880 list_add_tail(&queue.list, &sma->pending_alter);
1882 list_add_tail(&queue.list, &sma->pending_const);
1884 sma->complex_count++;
1887 queue.status = -EINTR;
1888 queue.sleeper = current;
1891 current->state = TASK_INTERRUPTIBLE;
1892 sem_unlock(sma, locknum);
1896 jiffies_left = schedule_timeout(jiffies_left);
1900 error = get_queue_result(&queue);
1902 if (error != -EINTR) {
1903 /* fast path: update_queue already obtained all requested
1905 * Perform a smp_mb(): User space could assume that semop()
1906 * is a memory barrier: Without the mb(), the cpu could
1907 * speculatively read in user space stale data that was
1908 * overwritten by the previous owner of the semaphore.
1916 sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1919 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1921 error = get_queue_result(&queue);
1924 * Array removed? If yes, leave without sem_unlock().
1933 * If queue.status != -EINTR we are woken up by another process.
1934 * Leave without unlink_queue(), but with sem_unlock().
1937 if (error != -EINTR) {
1938 goto out_unlock_free;
1942 * If an interrupt occurred we have to clean up the queue
1944 if (timeout && jiffies_left == 0)
1948 * If the wakeup was spurious, just retry
1950 if (error == -EINTR && !signal_pending(current))
1953 unlink_queue(sma, &queue);
1956 sem_unlock(sma, locknum);
1959 wake_up_sem_queue_do(&tasks);
1961 if(sops != fast_sops)
1966 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1969 return sys_semtimedop(semid, tsops, nsops, NULL);
1972 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1973 * parent and child tasks.
1976 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1978 struct sem_undo_list *undo_list;
1981 if (clone_flags & CLONE_SYSVSEM) {
1982 error = get_undo_list(&undo_list);
1985 atomic_inc(&undo_list->refcnt);
1986 tsk->sysvsem.undo_list = undo_list;
1988 tsk->sysvsem.undo_list = NULL;
1994 * add semadj values to semaphores, free undo structures.
1995 * undo structures are not freed when semaphore arrays are destroyed
1996 * so some of them may be out of date.
1997 * IMPLEMENTATION NOTE: There is some confusion over whether the
1998 * set of adjustments that needs to be done should be done in an atomic
1999 * manner or not. That is, if we are attempting to decrement the semval
2000 * should we queue up and wait until we can do so legally?
2001 * The original implementation attempted to do this (queue and wait).
2002 * The current implementation does not do so. The POSIX standard
2003 * and SVID should be consulted to determine what behavior is mandated.
2005 void exit_sem(struct task_struct *tsk)
2007 struct sem_undo_list *ulp;
2009 ulp = tsk->sysvsem.undo_list;
2012 tsk->sysvsem.undo_list = NULL;
2014 if (!atomic_dec_and_test(&ulp->refcnt))
2018 struct sem_array *sma;
2019 struct sem_undo *un;
2020 struct list_head tasks;
2024 un = list_entry_rcu(ulp->list_proc.next,
2025 struct sem_undo, list_proc);
2026 if (&un->list_proc == &ulp->list_proc)
2036 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
2037 /* exit_sem raced with IPC_RMID, nothing to do */
2043 sem_lock(sma, NULL, -1);
2044 un = __lookup_undo(ulp, semid);
2046 /* exit_sem raced with IPC_RMID+semget() that created
2047 * exactly the same semid. Nothing to do.
2049 sem_unlock(sma, -1);
2054 /* remove un from the linked lists */
2055 ipc_assert_locked_object(&sma->sem_perm);
2056 list_del(&un->list_id);
2058 spin_lock(&ulp->lock);
2059 list_del_rcu(&un->list_proc);
2060 spin_unlock(&ulp->lock);
2062 /* perform adjustments registered in un */
2063 for (i = 0; i < sma->sem_nsems; i++) {
2064 struct sem * semaphore = &sma->sem_base[i];
2065 if (un->semadj[i]) {
2066 semaphore->semval += un->semadj[i];
2068 * Range checks of the new semaphore value,
2069 * not defined by sus:
2070 * - Some unices ignore the undo entirely
2071 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
2072 * - some cap the value (e.g. FreeBSD caps
2073 * at 0, but doesn't enforce SEMVMX)
2075 * Linux caps the semaphore value, both at 0
2078 * Manfred <manfred@colorfullife.com>
2080 if (semaphore->semval < 0)
2081 semaphore->semval = 0;
2082 if (semaphore->semval > SEMVMX)
2083 semaphore->semval = SEMVMX;
2084 semaphore->sempid = task_tgid_vnr(current);
2087 /* maybe some queued-up processes were waiting for this */
2088 INIT_LIST_HEAD(&tasks);
2089 do_smart_update(sma, NULL, 0, 1, &tasks);
2090 sem_unlock(sma, -1);
2092 wake_up_sem_queue_do(&tasks);
2099 #ifdef CONFIG_PROC_FS
2100 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2102 struct user_namespace *user_ns = seq_user_ns(s);
2103 struct sem_array *sma = it;
2106 sem_otime = get_semotime(sma);
2108 return seq_printf(s,
2109 "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2114 from_kuid_munged(user_ns, sma->sem_perm.uid),
2115 from_kgid_munged(user_ns, sma->sem_perm.gid),
2116 from_kuid_munged(user_ns, sma->sem_perm.cuid),
2117 from_kgid_munged(user_ns, sma->sem_perm.cgid),