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 */
157 * linked list protection:
159 * sem_array.pending{_alter,_cont},
160 * sem_array.sem_undo: sem_lock() for read/write
161 * sem_undo.proc_next: only "current" is allowed to read/write that field.
165 #define sc_semmsl sem_ctls[0]
166 #define sc_semmns sem_ctls[1]
167 #define sc_semopm sem_ctls[2]
168 #define sc_semmni sem_ctls[3]
170 void sem_init_ns(struct ipc_namespace *ns)
172 ns->sc_semmsl = SEMMSL;
173 ns->sc_semmns = SEMMNS;
174 ns->sc_semopm = SEMOPM;
175 ns->sc_semmni = SEMMNI;
177 ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
181 void sem_exit_ns(struct ipc_namespace *ns)
183 free_ipcs(ns, &sem_ids(ns), freeary);
184 idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
188 void __init sem_init (void)
190 sem_init_ns(&init_ipc_ns);
191 ipc_init_proc_interface("sysvipc/sem",
192 " key semid perms nsems uid gid cuid cgid otime ctime\n",
193 IPC_SEM_IDS, sysvipc_sem_proc_show);
197 * unmerge_queues - unmerge queues, if possible.
198 * @sma: semaphore array
200 * The function unmerges the wait queues if complex_count is 0.
201 * It must be called prior to dropping the global semaphore array lock.
203 static void unmerge_queues(struct sem_array *sma)
205 struct sem_queue *q, *tq;
207 /* complex operations still around? */
208 if (sma->complex_count)
211 * We will switch back to simple mode.
212 * Move all pending operation back into the per-semaphore
215 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
217 curr = &sma->sem_base[q->sops[0].sem_num];
219 list_add_tail(&q->list, &curr->pending_alter);
221 INIT_LIST_HEAD(&sma->pending_alter);
225 * merge_queues - Merge single semop queues into global queue
226 * @sma: semaphore array
228 * This function merges all per-semaphore queues into the global queue.
229 * It is necessary to achieve FIFO ordering for the pending single-sop
230 * operations when a multi-semop operation must sleep.
231 * Only the alter operations must be moved, the const operations can stay.
233 static void merge_queues(struct sem_array *sma)
236 for (i = 0; i < sma->sem_nsems; i++) {
237 struct sem *sem = sma->sem_base + i;
239 list_splice_init(&sem->pending_alter, &sma->pending_alter);
244 * If the request contains only one semaphore operation, and there are
245 * no complex transactions pending, lock only the semaphore involved.
246 * Otherwise, lock the entire semaphore array, since we either have
247 * multiple semaphores in our own semops, or we need to look at
248 * semaphores from other pending complex operations.
250 * Carefully guard against sma->complex_count changing between zero
251 * and non-zero while we are spinning for the lock. The value of
252 * sma->complex_count cannot change while we are holding the lock,
253 * so sem_unlock should be fine.
255 * The global lock path checks that all the local locks have been released,
256 * checking each local lock once. This means that the local lock paths
257 * cannot start their critical sections while the global lock is held.
259 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
264 if (nsops == 1 && !sma->complex_count) {
265 struct sem *sem = sma->sem_base + sops->sem_num;
267 /* Lock just the semaphore we are interested in. */
268 spin_lock(&sem->lock);
271 * If sma->complex_count was set while we were spinning,
272 * we may need to look at things we did not lock here.
274 if (unlikely(sma->complex_count)) {
275 spin_unlock(&sem->lock);
280 * Another process is holding the global lock on the
281 * sem_array; we cannot enter our critical section,
282 * but have to wait for the global lock to be released.
284 if (unlikely(spin_is_locked(&sma->sem_perm.lock))) {
285 spin_unlock(&sem->lock);
286 spin_unlock_wait(&sma->sem_perm.lock);
290 locknum = sops->sem_num;
294 * Lock the semaphore array, and wait for all of the
295 * individual semaphore locks to go away. The code
296 * above ensures no new single-lock holders will enter
297 * their critical section while the array lock is held.
300 ipc_lock_object(&sma->sem_perm);
301 for (i = 0; i < sma->sem_nsems; i++) {
302 struct sem *sem = sma->sem_base + i;
303 spin_unlock_wait(&sem->lock);
310 static inline void sem_unlock(struct sem_array *sma, int locknum)
314 ipc_unlock_object(&sma->sem_perm);
316 struct sem *sem = sma->sem_base + locknum;
317 spin_unlock(&sem->lock);
322 * sem_lock_(check_) routines are called in the paths where the rw_mutex
325 * The caller holds the RCU read lock.
327 static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
328 int id, struct sembuf *sops, int nsops, int *locknum)
330 struct kern_ipc_perm *ipcp;
331 struct sem_array *sma;
333 ipcp = ipc_obtain_object(&sem_ids(ns), id);
335 return ERR_CAST(ipcp);
337 sma = container_of(ipcp, struct sem_array, sem_perm);
338 *locknum = sem_lock(sma, sops, nsops);
340 /* ipc_rmid() may have already freed the ID while sem_lock
341 * was spinning: verify that the structure is still valid
344 return container_of(ipcp, struct sem_array, sem_perm);
346 sem_unlock(sma, *locknum);
347 return ERR_PTR(-EINVAL);
350 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
352 struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
355 return ERR_CAST(ipcp);
357 return container_of(ipcp, struct sem_array, sem_perm);
360 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
363 struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
366 return ERR_CAST(ipcp);
368 return container_of(ipcp, struct sem_array, sem_perm);
371 static inline void sem_lock_and_putref(struct sem_array *sma)
373 sem_lock(sma, NULL, -1);
377 static inline void sem_putref(struct sem_array *sma)
382 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
384 ipc_rmid(&sem_ids(ns), &s->sem_perm);
388 * Lockless wakeup algorithm:
389 * Without the check/retry algorithm a lockless wakeup is possible:
390 * - queue.status is initialized to -EINTR before blocking.
391 * - wakeup is performed by
392 * * unlinking the queue entry from the pending list
393 * * setting queue.status to IN_WAKEUP
394 * This is the notification for the blocked thread that a
395 * result value is imminent.
396 * * call wake_up_process
397 * * set queue.status to the final value.
398 * - the previously blocked thread checks queue.status:
399 * * if it's IN_WAKEUP, then it must wait until the value changes
400 * * if it's not -EINTR, then the operation was completed by
401 * update_queue. semtimedop can return queue.status without
402 * performing any operation on the sem array.
403 * * otherwise it must acquire the spinlock and check what's up.
405 * The two-stage algorithm is necessary to protect against the following
407 * - if queue.status is set after wake_up_process, then the woken up idle
408 * thread could race forward and try (and fail) to acquire sma->lock
409 * before update_queue had a chance to set queue.status
410 * - if queue.status is written before wake_up_process and if the
411 * blocked process is woken up by a signal between writing
412 * queue.status and the wake_up_process, then the woken up
413 * process could return from semtimedop and die by calling
414 * sys_exit before wake_up_process is called. Then wake_up_process
415 * will oops, because the task structure is already invalid.
416 * (yes, this happened on s390 with sysv msg).
422 * newary - Create a new semaphore set
424 * @params: ptr to the structure that contains key, semflg and nsems
426 * Called with sem_ids.rw_mutex held (as a writer)
429 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
433 struct sem_array *sma;
435 key_t key = params->key;
436 int nsems = params->u.nsems;
437 int semflg = params->flg;
442 if (ns->used_sems + nsems > ns->sc_semmns)
445 size = sizeof (*sma) + nsems * sizeof (struct sem);
446 sma = ipc_rcu_alloc(size);
450 memset (sma, 0, size);
452 sma->sem_perm.mode = (semflg & S_IRWXUGO);
453 sma->sem_perm.key = key;
455 sma->sem_perm.security = NULL;
456 retval = security_sem_alloc(sma);
462 id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
464 security_sem_free(sma);
468 ns->used_sems += nsems;
470 sma->sem_base = (struct sem *) &sma[1];
472 for (i = 0; i < nsems; i++) {
473 INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
474 INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
475 spin_lock_init(&sma->sem_base[i].lock);
478 sma->complex_count = 0;
479 INIT_LIST_HEAD(&sma->pending_alter);
480 INIT_LIST_HEAD(&sma->pending_const);
481 INIT_LIST_HEAD(&sma->list_id);
482 sma->sem_nsems = nsems;
483 sma->sem_ctime = get_seconds();
487 return sma->sem_perm.id;
492 * Called with sem_ids.rw_mutex and ipcp locked.
494 static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
496 struct sem_array *sma;
498 sma = container_of(ipcp, struct sem_array, sem_perm);
499 return security_sem_associate(sma, semflg);
503 * Called with sem_ids.rw_mutex and ipcp locked.
505 static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
506 struct ipc_params *params)
508 struct sem_array *sma;
510 sma = container_of(ipcp, struct sem_array, sem_perm);
511 if (params->u.nsems > sma->sem_nsems)
517 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
519 struct ipc_namespace *ns;
520 struct ipc_ops sem_ops;
521 struct ipc_params sem_params;
523 ns = current->nsproxy->ipc_ns;
525 if (nsems < 0 || nsems > ns->sc_semmsl)
528 sem_ops.getnew = newary;
529 sem_ops.associate = sem_security;
530 sem_ops.more_checks = sem_more_checks;
532 sem_params.key = key;
533 sem_params.flg = semflg;
534 sem_params.u.nsems = nsems;
536 return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
540 * Determine whether a sequence of semaphore operations would succeed
541 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
544 static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
545 int nsops, struct sem_undo *un, int pid)
551 for (sop = sops; sop < sops + nsops; sop++) {
552 curr = sma->sem_base + sop->sem_num;
553 sem_op = sop->sem_op;
554 result = curr->semval;
556 if (!sem_op && result)
564 if (sop->sem_flg & SEM_UNDO) {
565 int undo = un->semadj[sop->sem_num] - sem_op;
567 * Exceeding the undo range is an error.
569 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
572 curr->semval = result;
576 while (sop >= sops) {
577 sma->sem_base[sop->sem_num].sempid = pid;
578 if (sop->sem_flg & SEM_UNDO)
579 un->semadj[sop->sem_num] -= sop->sem_op;
590 if (sop->sem_flg & IPC_NOWAIT)
597 while (sop >= sops) {
598 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
605 /** wake_up_sem_queue_prepare(q, error): Prepare wake-up
606 * @q: queue entry that must be signaled
607 * @error: Error value for the signal
609 * Prepare the wake-up of the queue entry q.
611 static void wake_up_sem_queue_prepare(struct list_head *pt,
612 struct sem_queue *q, int error)
614 if (list_empty(pt)) {
616 * Hold preempt off so that we don't get preempted and have the
617 * wakee busy-wait until we're scheduled back on.
621 q->status = IN_WAKEUP;
624 list_add_tail(&q->list, pt);
628 * wake_up_sem_queue_do(pt) - do the actual wake-up
629 * @pt: list of tasks to be woken up
631 * Do the actual wake-up.
632 * The function is called without any locks held, thus the semaphore array
633 * could be destroyed already and the tasks can disappear as soon as the
634 * status is set to the actual return code.
636 static void wake_up_sem_queue_do(struct list_head *pt)
638 struct sem_queue *q, *t;
641 did_something = !list_empty(pt);
642 list_for_each_entry_safe(q, t, pt, list) {
643 wake_up_process(q->sleeper);
644 /* q can disappear immediately after writing q->status. */
652 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
656 sma->complex_count--;
659 /** check_restart(sma, q)
660 * @sma: semaphore array
661 * @q: the operation that just completed
663 * update_queue is O(N^2) when it restarts scanning the whole queue of
664 * waiting operations. Therefore this function checks if the restart is
665 * really necessary. It is called after a previously waiting operation
666 * modified the array.
667 * Note that wait-for-zero operations are handled without restart.
669 static int check_restart(struct sem_array *sma, struct sem_queue *q)
671 /* pending complex alter operations are too difficult to analyse */
672 if (!list_empty(&sma->pending_alter))
675 /* we were a sleeping complex operation. Too difficult */
679 /* It is impossible that someone waits for the new value:
680 * - complex operations always restart.
681 * - wait-for-zero are handled seperately.
682 * - q is a previously sleeping simple operation that
683 * altered the array. It must be a decrement, because
684 * simple increments never sleep.
685 * - If there are older (higher priority) decrements
686 * in the queue, then they have observed the original
687 * semval value and couldn't proceed. The operation
688 * decremented to value - thus they won't proceed either.
694 * wake_const_ops(sma, semnum, pt) - Wake up non-alter tasks
695 * @sma: semaphore array.
696 * @semnum: semaphore that was modified.
697 * @pt: list head for the tasks that must be woken up.
699 * wake_const_ops must be called after a semaphore in a semaphore array
700 * was set to 0. If complex const operations are pending, wake_const_ops must
701 * be called with semnum = -1, as well as with the number of each modified
703 * The tasks that must be woken up are added to @pt. The return code
704 * is stored in q->pid.
705 * The function returns 1 if at least one operation was completed successfully.
707 static int wake_const_ops(struct sem_array *sma, int semnum,
708 struct list_head *pt)
711 struct list_head *walk;
712 struct list_head *pending_list;
713 int semop_completed = 0;
716 pending_list = &sma->pending_const;
718 pending_list = &sma->sem_base[semnum].pending_const;
720 walk = pending_list->next;
721 while (walk != pending_list) {
724 q = container_of(walk, struct sem_queue, list);
727 error = try_atomic_semop(sma, q->sops, q->nsops,
731 /* operation completed, remove from queue & wakeup */
733 unlink_queue(sma, q);
735 wake_up_sem_queue_prepare(pt, q, error);
740 return semop_completed;
744 * do_smart_wakeup_zero(sma, sops, nsops, pt) - wakeup all wait for zero tasks
745 * @sma: semaphore array
746 * @sops: operations that were performed
747 * @nsops: number of operations
748 * @pt: list head of the tasks that must be woken up.
750 * do_smart_wakeup_zero() checks all required queue for wait-for-zero
751 * operations, based on the actual changes that were performed on the
753 * The function returns 1 if at least one operation was completed successfully.
755 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
756 int nsops, struct list_head *pt)
759 int semop_completed = 0;
762 /* first: the per-semaphore queues, if known */
764 for (i = 0; i < nsops; i++) {
765 int num = sops[i].sem_num;
767 if (sma->sem_base[num].semval == 0) {
769 semop_completed |= wake_const_ops(sma, num, pt);
774 * No sops means modified semaphores not known.
775 * Assume all were changed.
777 for (i = 0; i < sma->sem_nsems; i++) {
778 if (sma->sem_base[i].semval == 0) {
780 semop_completed |= wake_const_ops(sma, i, pt);
785 * If one of the modified semaphores got 0,
786 * then check the global queue, too.
789 semop_completed |= wake_const_ops(sma, -1, pt);
791 return semop_completed;
796 * update_queue(sma, semnum): Look for tasks that can be completed.
797 * @sma: semaphore array.
798 * @semnum: semaphore that was modified.
799 * @pt: list head for the tasks that must be woken up.
801 * update_queue must be called after a semaphore in a semaphore array
802 * was modified. If multiple semaphores were modified, update_queue must
803 * be called with semnum = -1, as well as with the number of each modified
805 * The tasks that must be woken up are added to @pt. The return code
806 * is stored in q->pid.
807 * The function internally checks if const operations can now succeed.
809 * The function return 1 if at least one semop was completed successfully.
811 static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
814 struct list_head *walk;
815 struct list_head *pending_list;
816 int semop_completed = 0;
819 pending_list = &sma->pending_alter;
821 pending_list = &sma->sem_base[semnum].pending_alter;
824 walk = pending_list->next;
825 while (walk != pending_list) {
828 q = container_of(walk, struct sem_queue, list);
831 /* If we are scanning the single sop, per-semaphore list of
832 * one semaphore and that semaphore is 0, then it is not
833 * necessary to scan further: simple increments
834 * that affect only one entry succeed immediately and cannot
835 * be in the per semaphore pending queue, and decrements
836 * cannot be successful if the value is already 0.
838 if (semnum != -1 && sma->sem_base[semnum].semval == 0)
841 error = try_atomic_semop(sma, q->sops, q->nsops,
844 /* Does q->sleeper still need to sleep? */
848 unlink_queue(sma, q);
854 do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
855 restart = check_restart(sma, q);
858 wake_up_sem_queue_prepare(pt, q, error);
862 return semop_completed;
866 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
867 * @sma: semaphore array
868 * @sops: operations that were performed
869 * @nsops: number of operations
870 * @otime: force setting otime
871 * @pt: list head of the tasks that must be woken up.
873 * do_smart_update() does the required calls to update_queue and wakeup_zero,
874 * based on the actual changes that were performed on the semaphore array.
875 * Note that the function does not do the actual wake-up: the caller is
876 * responsible for calling wake_up_sem_queue_do(@pt).
877 * It is safe to perform this call after dropping all locks.
879 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
880 int otime, struct list_head *pt)
884 otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
886 if (!list_empty(&sma->pending_alter)) {
887 /* semaphore array uses the global queue - just process it. */
888 otime |= update_queue(sma, -1, pt);
892 * No sops, thus the modified semaphores are not
895 for (i = 0; i < sma->sem_nsems; i++)
896 otime |= update_queue(sma, i, pt);
899 * Check the semaphores that were increased:
900 * - No complex ops, thus all sleeping ops are
902 * - if we decreased the value, then any sleeping
903 * semaphore ops wont be able to run: If the
904 * previous value was too small, then the new
905 * value will be too small, too.
907 for (i = 0; i < nsops; i++) {
908 if (sops[i].sem_op > 0) {
909 otime |= update_queue(sma,
910 sops[i].sem_num, pt);
917 sma->sem_base[0].sem_otime = get_seconds();
919 sma->sem_base[sops[0].sem_num].sem_otime =
926 /* The following counts are associated to each semaphore:
927 * semncnt number of tasks waiting on semval being nonzero
928 * semzcnt number of tasks waiting on semval being zero
929 * This model assumes that a task waits on exactly one semaphore.
930 * Since semaphore operations are to be performed atomically, tasks actually
931 * wait on a whole sequence of semaphores simultaneously.
932 * The counts we return here are a rough approximation, but still
933 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
935 static int count_semncnt (struct sem_array * sma, ushort semnum)
938 struct sem_queue * q;
941 list_for_each_entry(q, &sma->sem_base[semnum].pending_alter, list) {
942 struct sembuf * sops = q->sops;
943 BUG_ON(sops->sem_num != semnum);
944 if ((sops->sem_op < 0) && !(sops->sem_flg & IPC_NOWAIT))
948 list_for_each_entry(q, &sma->pending_alter, list) {
949 struct sembuf * sops = q->sops;
950 int nsops = q->nsops;
952 for (i = 0; i < nsops; i++)
953 if (sops[i].sem_num == semnum
954 && (sops[i].sem_op < 0)
955 && !(sops[i].sem_flg & IPC_NOWAIT))
961 static int count_semzcnt (struct sem_array * sma, ushort semnum)
964 struct sem_queue * q;
967 list_for_each_entry(q, &sma->sem_base[semnum].pending_const, list) {
968 struct sembuf * sops = q->sops;
969 BUG_ON(sops->sem_num != semnum);
970 if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
974 list_for_each_entry(q, &sma->pending_const, list) {
975 struct sembuf * sops = q->sops;
976 int nsops = q->nsops;
978 for (i = 0; i < nsops; i++)
979 if (sops[i].sem_num == semnum
980 && (sops[i].sem_op == 0)
981 && !(sops[i].sem_flg & IPC_NOWAIT))
987 /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
988 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
989 * remains locked on exit.
991 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
993 struct sem_undo *un, *tu;
994 struct sem_queue *q, *tq;
995 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
996 struct list_head tasks;
999 /* Free the existing undo structures for this semaphore set. */
1000 ipc_assert_locked_object(&sma->sem_perm);
1001 list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1002 list_del(&un->list_id);
1003 spin_lock(&un->ulp->lock);
1005 list_del_rcu(&un->list_proc);
1006 spin_unlock(&un->ulp->lock);
1010 /* Wake up all pending processes and let them fail with EIDRM. */
1011 INIT_LIST_HEAD(&tasks);
1012 list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1013 unlink_queue(sma, q);
1014 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1017 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1018 unlink_queue(sma, q);
1019 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1021 for (i = 0; i < sma->sem_nsems; i++) {
1022 struct sem *sem = sma->sem_base + i;
1023 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1024 unlink_queue(sma, q);
1025 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1027 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1028 unlink_queue(sma, q);
1029 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1033 /* Remove the semaphore set from the IDR */
1035 sem_unlock(sma, -1);
1038 wake_up_sem_queue_do(&tasks);
1039 ns->used_sems -= sma->sem_nsems;
1040 security_sem_free(sma);
1041 ipc_rcu_putref(sma);
1044 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1048 return copy_to_user(buf, in, sizeof(*in));
1051 struct semid_ds out;
1053 memset(&out, 0, sizeof(out));
1055 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1057 out.sem_otime = in->sem_otime;
1058 out.sem_ctime = in->sem_ctime;
1059 out.sem_nsems = in->sem_nsems;
1061 return copy_to_user(buf, &out, sizeof(out));
1068 static time_t get_semotime(struct sem_array *sma)
1073 res = sma->sem_base[0].sem_otime;
1074 for (i = 1; i < sma->sem_nsems; i++) {
1075 time_t to = sma->sem_base[i].sem_otime;
1083 static int semctl_nolock(struct ipc_namespace *ns, int semid,
1084 int cmd, int version, void __user *p)
1087 struct sem_array *sma;
1093 struct seminfo seminfo;
1096 err = security_sem_semctl(NULL, cmd);
1100 memset(&seminfo,0,sizeof(seminfo));
1101 seminfo.semmni = ns->sc_semmni;
1102 seminfo.semmns = ns->sc_semmns;
1103 seminfo.semmsl = ns->sc_semmsl;
1104 seminfo.semopm = ns->sc_semopm;
1105 seminfo.semvmx = SEMVMX;
1106 seminfo.semmnu = SEMMNU;
1107 seminfo.semmap = SEMMAP;
1108 seminfo.semume = SEMUME;
1109 down_read(&sem_ids(ns).rw_mutex);
1110 if (cmd == SEM_INFO) {
1111 seminfo.semusz = sem_ids(ns).in_use;
1112 seminfo.semaem = ns->used_sems;
1114 seminfo.semusz = SEMUSZ;
1115 seminfo.semaem = SEMAEM;
1117 max_id = ipc_get_maxid(&sem_ids(ns));
1118 up_read(&sem_ids(ns).rw_mutex);
1119 if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1121 return (max_id < 0) ? 0: max_id;
1126 struct semid64_ds tbuf;
1129 memset(&tbuf, 0, sizeof(tbuf));
1132 if (cmd == SEM_STAT) {
1133 sma = sem_obtain_object(ns, semid);
1138 id = sma->sem_perm.id;
1140 sma = sem_obtain_object_check(ns, semid);
1148 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1151 err = security_sem_semctl(sma, cmd);
1155 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1156 tbuf.sem_otime = get_semotime(sma);
1157 tbuf.sem_ctime = sma->sem_ctime;
1158 tbuf.sem_nsems = sma->sem_nsems;
1160 if (copy_semid_to_user(p, &tbuf, version))
1172 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1175 struct sem_undo *un;
1176 struct sem_array *sma;
1179 struct list_head tasks;
1181 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1182 /* big-endian 64bit */
1185 /* 32bit or little-endian 64bit */
1189 if (val > SEMVMX || val < 0)
1192 INIT_LIST_HEAD(&tasks);
1195 sma = sem_obtain_object_check(ns, semid);
1198 return PTR_ERR(sma);
1201 if (semnum < 0 || semnum >= sma->sem_nsems) {
1207 if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1212 err = security_sem_semctl(sma, SETVAL);
1218 sem_lock(sma, NULL, -1);
1220 curr = &sma->sem_base[semnum];
1222 ipc_assert_locked_object(&sma->sem_perm);
1223 list_for_each_entry(un, &sma->list_id, list_id)
1224 un->semadj[semnum] = 0;
1227 curr->sempid = task_tgid_vnr(current);
1228 sma->sem_ctime = get_seconds();
1229 /* maybe some queued-up processes were waiting for this */
1230 do_smart_update(sma, NULL, 0, 0, &tasks);
1231 sem_unlock(sma, -1);
1233 wake_up_sem_queue_do(&tasks);
1237 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1238 int cmd, void __user *p)
1240 struct sem_array *sma;
1243 ushort fast_sem_io[SEMMSL_FAST];
1244 ushort* sem_io = fast_sem_io;
1245 struct list_head tasks;
1247 INIT_LIST_HEAD(&tasks);
1250 sma = sem_obtain_object_check(ns, semid);
1253 return PTR_ERR(sma);
1256 nsems = sma->sem_nsems;
1259 if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1260 goto out_rcu_wakeup;
1262 err = security_sem_semctl(sma, cmd);
1264 goto out_rcu_wakeup;
1270 ushort __user *array = p;
1273 sem_lock(sma, NULL, -1);
1274 if(nsems > SEMMSL_FAST) {
1275 if (!ipc_rcu_getref(sma)) {
1276 sem_unlock(sma, -1);
1281 sem_unlock(sma, -1);
1283 sem_io = ipc_alloc(sizeof(ushort)*nsems);
1284 if(sem_io == NULL) {
1290 sem_lock_and_putref(sma);
1291 if (sma->sem_perm.deleted) {
1292 sem_unlock(sma, -1);
1298 for (i = 0; i < sma->sem_nsems; i++)
1299 sem_io[i] = sma->sem_base[i].semval;
1300 sem_unlock(sma, -1);
1303 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1310 struct sem_undo *un;
1312 if (!ipc_rcu_getref(sma)) {
1318 if(nsems > SEMMSL_FAST) {
1319 sem_io = ipc_alloc(sizeof(ushort)*nsems);
1320 if(sem_io == NULL) {
1326 if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) {
1332 for (i = 0; i < nsems; i++) {
1333 if (sem_io[i] > SEMVMX) {
1340 sem_lock_and_putref(sma);
1341 if (sma->sem_perm.deleted) {
1342 sem_unlock(sma, -1);
1348 for (i = 0; i < nsems; i++)
1349 sma->sem_base[i].semval = sem_io[i];
1351 ipc_assert_locked_object(&sma->sem_perm);
1352 list_for_each_entry(un, &sma->list_id, list_id) {
1353 for (i = 0; i < nsems; i++)
1356 sma->sem_ctime = get_seconds();
1357 /* maybe some queued-up processes were waiting for this */
1358 do_smart_update(sma, NULL, 0, 0, &tasks);
1362 /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1365 if (semnum < 0 || semnum >= nsems)
1366 goto out_rcu_wakeup;
1368 sem_lock(sma, NULL, -1);
1369 curr = &sma->sem_base[semnum];
1379 err = count_semncnt(sma,semnum);
1382 err = count_semzcnt(sma,semnum);
1387 sem_unlock(sma, -1);
1390 wake_up_sem_queue_do(&tasks);
1392 if(sem_io != fast_sem_io)
1393 ipc_free(sem_io, sizeof(ushort)*nsems);
1397 static inline unsigned long
1398 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1402 if (copy_from_user(out, buf, sizeof(*out)))
1407 struct semid_ds tbuf_old;
1409 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1412 out->sem_perm.uid = tbuf_old.sem_perm.uid;
1413 out->sem_perm.gid = tbuf_old.sem_perm.gid;
1414 out->sem_perm.mode = tbuf_old.sem_perm.mode;
1424 * This function handles some semctl commands which require the rw_mutex
1425 * to be held in write mode.
1426 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1428 static int semctl_down(struct ipc_namespace *ns, int semid,
1429 int cmd, int version, void __user *p)
1431 struct sem_array *sma;
1433 struct semid64_ds semid64;
1434 struct kern_ipc_perm *ipcp;
1436 if(cmd == IPC_SET) {
1437 if (copy_semid_from_user(&semid64, p, version))
1441 down_write(&sem_ids(ns).rw_mutex);
1444 ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1445 &semid64.sem_perm, 0);
1447 err = PTR_ERR(ipcp);
1451 sma = container_of(ipcp, struct sem_array, sem_perm);
1453 err = security_sem_semctl(sma, cmd);
1459 sem_lock(sma, NULL, -1);
1460 /* freeary unlocks the ipc object and rcu */
1464 sem_lock(sma, NULL, -1);
1465 err = ipc_update_perm(&semid64.sem_perm, ipcp);
1468 sma->sem_ctime = get_seconds();
1476 sem_unlock(sma, -1);
1480 up_write(&sem_ids(ns).rw_mutex);
1484 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1487 struct ipc_namespace *ns;
1488 void __user *p = (void __user *)arg;
1493 version = ipc_parse_version(&cmd);
1494 ns = current->nsproxy->ipc_ns;
1501 return semctl_nolock(ns, semid, cmd, version, p);
1508 return semctl_main(ns, semid, semnum, cmd, p);
1510 return semctl_setval(ns, semid, semnum, arg);
1513 return semctl_down(ns, semid, cmd, version, p);
1519 /* If the task doesn't already have a undo_list, then allocate one
1520 * here. We guarantee there is only one thread using this undo list,
1521 * and current is THE ONE
1523 * If this allocation and assignment succeeds, but later
1524 * portions of this code fail, there is no need to free the sem_undo_list.
1525 * Just let it stay associated with the task, and it'll be freed later
1528 * This can block, so callers must hold no locks.
1530 static inline int get_undo_list(struct sem_undo_list **undo_listp)
1532 struct sem_undo_list *undo_list;
1534 undo_list = current->sysvsem.undo_list;
1536 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1537 if (undo_list == NULL)
1539 spin_lock_init(&undo_list->lock);
1540 atomic_set(&undo_list->refcnt, 1);
1541 INIT_LIST_HEAD(&undo_list->list_proc);
1543 current->sysvsem.undo_list = undo_list;
1545 *undo_listp = undo_list;
1549 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1551 struct sem_undo *un;
1553 list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1554 if (un->semid == semid)
1560 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1562 struct sem_undo *un;
1564 assert_spin_locked(&ulp->lock);
1566 un = __lookup_undo(ulp, semid);
1568 list_del_rcu(&un->list_proc);
1569 list_add_rcu(&un->list_proc, &ulp->list_proc);
1575 * find_alloc_undo - Lookup (and if not present create) undo array
1577 * @semid: semaphore array id
1579 * The function looks up (and if not present creates) the undo structure.
1580 * The size of the undo structure depends on the size of the semaphore
1581 * array, thus the alloc path is not that straightforward.
1582 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1583 * performs a rcu_read_lock().
1585 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1587 struct sem_array *sma;
1588 struct sem_undo_list *ulp;
1589 struct sem_undo *un, *new;
1592 error = get_undo_list(&ulp);
1594 return ERR_PTR(error);
1597 spin_lock(&ulp->lock);
1598 un = lookup_undo(ulp, semid);
1599 spin_unlock(&ulp->lock);
1600 if (likely(un!=NULL))
1603 /* no undo structure around - allocate one. */
1604 /* step 1: figure out the size of the semaphore array */
1605 sma = sem_obtain_object_check(ns, semid);
1608 return ERR_CAST(sma);
1611 nsems = sma->sem_nsems;
1612 if (!ipc_rcu_getref(sma)) {
1614 un = ERR_PTR(-EIDRM);
1619 /* step 2: allocate new undo structure */
1620 new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1623 return ERR_PTR(-ENOMEM);
1626 /* step 3: Acquire the lock on semaphore array */
1628 sem_lock_and_putref(sma);
1629 if (sma->sem_perm.deleted) {
1630 sem_unlock(sma, -1);
1633 un = ERR_PTR(-EIDRM);
1636 spin_lock(&ulp->lock);
1639 * step 4: check for races: did someone else allocate the undo struct?
1641 un = lookup_undo(ulp, semid);
1646 /* step 5: initialize & link new undo structure */
1647 new->semadj = (short *) &new[1];
1650 assert_spin_locked(&ulp->lock);
1651 list_add_rcu(&new->list_proc, &ulp->list_proc);
1652 ipc_assert_locked_object(&sma->sem_perm);
1653 list_add(&new->list_id, &sma->list_id);
1657 spin_unlock(&ulp->lock);
1658 sem_unlock(sma, -1);
1665 * get_queue_result - Retrieve the result code from sem_queue
1666 * @q: Pointer to queue structure
1668 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1669 * q->status, then we must loop until the value is replaced with the final
1670 * value: This may happen if a task is woken up by an unrelated event (e.g.
1671 * signal) and in parallel the task is woken up by another task because it got
1672 * the requested semaphores.
1674 * The function can be called with or without holding the semaphore spinlock.
1676 static int get_queue_result(struct sem_queue *q)
1681 while (unlikely(error == IN_WAKEUP)) {
1690 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1691 unsigned, nsops, const struct timespec __user *, timeout)
1693 int error = -EINVAL;
1694 struct sem_array *sma;
1695 struct sembuf fast_sops[SEMOPM_FAST];
1696 struct sembuf* sops = fast_sops, *sop;
1697 struct sem_undo *un;
1698 int undos = 0, alter = 0, max, locknum;
1699 struct sem_queue queue;
1700 unsigned long jiffies_left = 0;
1701 struct ipc_namespace *ns;
1702 struct list_head tasks;
1704 ns = current->nsproxy->ipc_ns;
1706 if (nsops < 1 || semid < 0)
1708 if (nsops > ns->sc_semopm)
1710 if(nsops > SEMOPM_FAST) {
1711 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1715 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1720 struct timespec _timeout;
1721 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1725 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1726 _timeout.tv_nsec >= 1000000000L) {
1730 jiffies_left = timespec_to_jiffies(&_timeout);
1733 for (sop = sops; sop < sops + nsops; sop++) {
1734 if (sop->sem_num >= max)
1736 if (sop->sem_flg & SEM_UNDO)
1738 if (sop->sem_op != 0)
1742 INIT_LIST_HEAD(&tasks);
1745 /* On success, find_alloc_undo takes the rcu_read_lock */
1746 un = find_alloc_undo(ns, semid);
1748 error = PTR_ERR(un);
1756 sma = sem_obtain_object_check(ns, semid);
1759 error = PTR_ERR(sma);
1764 if (max >= sma->sem_nsems)
1765 goto out_rcu_wakeup;
1768 if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1769 goto out_rcu_wakeup;
1771 error = security_sem_semop(sma, sops, nsops, alter);
1773 goto out_rcu_wakeup;
1776 * semid identifiers are not unique - find_alloc_undo may have
1777 * allocated an undo structure, it was invalidated by an RMID
1778 * and now a new array with received the same id. Check and fail.
1779 * This case can be detected checking un->semid. The existence of
1780 * "un" itself is guaranteed by rcu.
1783 locknum = sem_lock(sma, sops, nsops);
1784 if (un && un->semid == -1)
1785 goto out_unlock_free;
1787 error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
1789 if (alter && error == 0)
1790 do_smart_update(sma, sops, nsops, 1, &tasks);
1792 goto out_unlock_free;
1795 /* We need to sleep on this operation, so we put the current
1796 * task into the pending queue and go to sleep.
1800 queue.nsops = nsops;
1802 queue.pid = task_tgid_vnr(current);
1803 queue.alter = alter;
1807 curr = &sma->sem_base[sops->sem_num];
1810 if (sma->complex_count) {
1811 list_add_tail(&queue.list,
1812 &sma->pending_alter);
1815 list_add_tail(&queue.list,
1816 &curr->pending_alter);
1819 list_add_tail(&queue.list, &curr->pending_const);
1822 if (!sma->complex_count)
1826 list_add_tail(&queue.list, &sma->pending_alter);
1828 list_add_tail(&queue.list, &sma->pending_const);
1830 sma->complex_count++;
1833 queue.status = -EINTR;
1834 queue.sleeper = current;
1837 current->state = TASK_INTERRUPTIBLE;
1838 sem_unlock(sma, locknum);
1842 jiffies_left = schedule_timeout(jiffies_left);
1846 error = get_queue_result(&queue);
1848 if (error != -EINTR) {
1849 /* fast path: update_queue already obtained all requested
1851 * Perform a smp_mb(): User space could assume that semop()
1852 * is a memory barrier: Without the mb(), the cpu could
1853 * speculatively read in user space stale data that was
1854 * overwritten by the previous owner of the semaphore.
1862 sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1865 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1867 error = get_queue_result(&queue);
1870 * Array removed? If yes, leave without sem_unlock().
1879 * If queue.status != -EINTR we are woken up by another process.
1880 * Leave without unlink_queue(), but with sem_unlock().
1883 if (error != -EINTR) {
1884 goto out_unlock_free;
1888 * If an interrupt occurred we have to clean up the queue
1890 if (timeout && jiffies_left == 0)
1894 * If the wakeup was spurious, just retry
1896 if (error == -EINTR && !signal_pending(current))
1899 unlink_queue(sma, &queue);
1902 sem_unlock(sma, locknum);
1905 wake_up_sem_queue_do(&tasks);
1907 if(sops != fast_sops)
1912 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1915 return sys_semtimedop(semid, tsops, nsops, NULL);
1918 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1919 * parent and child tasks.
1922 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1924 struct sem_undo_list *undo_list;
1927 if (clone_flags & CLONE_SYSVSEM) {
1928 error = get_undo_list(&undo_list);
1931 atomic_inc(&undo_list->refcnt);
1932 tsk->sysvsem.undo_list = undo_list;
1934 tsk->sysvsem.undo_list = NULL;
1940 * add semadj values to semaphores, free undo structures.
1941 * undo structures are not freed when semaphore arrays are destroyed
1942 * so some of them may be out of date.
1943 * IMPLEMENTATION NOTE: There is some confusion over whether the
1944 * set of adjustments that needs to be done should be done in an atomic
1945 * manner or not. That is, if we are attempting to decrement the semval
1946 * should we queue up and wait until we can do so legally?
1947 * The original implementation attempted to do this (queue and wait).
1948 * The current implementation does not do so. The POSIX standard
1949 * and SVID should be consulted to determine what behavior is mandated.
1951 void exit_sem(struct task_struct *tsk)
1953 struct sem_undo_list *ulp;
1955 ulp = tsk->sysvsem.undo_list;
1958 tsk->sysvsem.undo_list = NULL;
1960 if (!atomic_dec_and_test(&ulp->refcnt))
1964 struct sem_array *sma;
1965 struct sem_undo *un;
1966 struct list_head tasks;
1970 un = list_entry_rcu(ulp->list_proc.next,
1971 struct sem_undo, list_proc);
1972 if (&un->list_proc == &ulp->list_proc)
1982 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
1983 /* exit_sem raced with IPC_RMID, nothing to do */
1989 sem_lock(sma, NULL, -1);
1990 un = __lookup_undo(ulp, semid);
1992 /* exit_sem raced with IPC_RMID+semget() that created
1993 * exactly the same semid. Nothing to do.
1995 sem_unlock(sma, -1);
2000 /* remove un from the linked lists */
2001 ipc_assert_locked_object(&sma->sem_perm);
2002 list_del(&un->list_id);
2004 spin_lock(&ulp->lock);
2005 list_del_rcu(&un->list_proc);
2006 spin_unlock(&ulp->lock);
2008 /* perform adjustments registered in un */
2009 for (i = 0; i < sma->sem_nsems; i++) {
2010 struct sem * semaphore = &sma->sem_base[i];
2011 if (un->semadj[i]) {
2012 semaphore->semval += un->semadj[i];
2014 * Range checks of the new semaphore value,
2015 * not defined by sus:
2016 * - Some unices ignore the undo entirely
2017 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
2018 * - some cap the value (e.g. FreeBSD caps
2019 * at 0, but doesn't enforce SEMVMX)
2021 * Linux caps the semaphore value, both at 0
2024 * Manfred <manfred@colorfullife.com>
2026 if (semaphore->semval < 0)
2027 semaphore->semval = 0;
2028 if (semaphore->semval > SEMVMX)
2029 semaphore->semval = SEMVMX;
2030 semaphore->sempid = task_tgid_vnr(current);
2033 /* maybe some queued-up processes were waiting for this */
2034 INIT_LIST_HEAD(&tasks);
2035 do_smart_update(sma, NULL, 0, 1, &tasks);
2036 sem_unlock(sma, -1);
2038 wake_up_sem_queue_do(&tasks);
2045 #ifdef CONFIG_PROC_FS
2046 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2048 struct user_namespace *user_ns = seq_user_ns(s);
2049 struct sem_array *sma = it;
2052 sem_otime = get_semotime(sma);
2054 return seq_printf(s,
2055 "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2060 from_kuid_munged(user_ns, sma->sem_perm.uid),
2061 from_kgid_munged(user_ns, sma->sem_perm.gid),
2062 from_kuid_munged(user_ns, sma->sem_perm.cuid),
2063 from_kgid_munged(user_ns, sma->sem_perm.cgid),