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 #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
95 #define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
96 #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
98 static int newary(struct ipc_namespace
*, struct ipc_params
*);
99 static void freeary(struct ipc_namespace
*, struct kern_ipc_perm
*);
100 #ifdef CONFIG_PROC_FS
101 static int sysvipc_sem_proc_show(struct seq_file
*s
, void *it
);
104 #define SEMMSL_FAST 256 /* 512 bytes on stack */
105 #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
108 * linked list protection:
110 * sem_array.sem_pending{,last},
111 * sem_array.sem_undo: sem_lock() for read/write
112 * sem_undo.proc_next: only "current" is allowed to read/write that field.
116 #define sc_semmsl sem_ctls[0]
117 #define sc_semmns sem_ctls[1]
118 #define sc_semopm sem_ctls[2]
119 #define sc_semmni sem_ctls[3]
121 void sem_init_ns(struct ipc_namespace
*ns
)
123 ns
->sc_semmsl
= SEMMSL
;
124 ns
->sc_semmns
= SEMMNS
;
125 ns
->sc_semopm
= SEMOPM
;
126 ns
->sc_semmni
= SEMMNI
;
128 ipc_init_ids(&ns
->ids
[IPC_SEM_IDS
]);
132 void sem_exit_ns(struct ipc_namespace
*ns
)
134 free_ipcs(ns
, &sem_ids(ns
), freeary
);
135 idr_destroy(&ns
->ids
[IPC_SEM_IDS
].ipcs_idr
);
139 void __init
sem_init (void)
141 sem_init_ns(&init_ipc_ns
);
142 ipc_init_proc_interface("sysvipc/sem",
143 " key semid perms nsems uid gid cuid cgid otime ctime\n",
144 IPC_SEM_IDS
, sysvipc_sem_proc_show
);
148 * sem_lock_(check_) routines are called in the paths where the rw_mutex
151 static inline struct sem_array
*sem_lock(struct ipc_namespace
*ns
, int id
)
153 struct kern_ipc_perm
*ipcp
= ipc_lock(&sem_ids(ns
), id
);
156 return (struct sem_array
*)ipcp
;
158 return container_of(ipcp
, struct sem_array
, sem_perm
);
161 static inline struct sem_array
*sem_lock_check(struct ipc_namespace
*ns
,
164 struct kern_ipc_perm
*ipcp
= ipc_lock_check(&sem_ids(ns
), id
);
167 return (struct sem_array
*)ipcp
;
169 return container_of(ipcp
, struct sem_array
, sem_perm
);
172 static inline void sem_lock_and_putref(struct sem_array
*sma
)
174 ipc_lock_by_ptr(&sma
->sem_perm
);
178 static inline void sem_getref_and_unlock(struct sem_array
*sma
)
181 ipc_unlock(&(sma
)->sem_perm
);
184 static inline void sem_putref(struct sem_array
*sma
)
186 ipc_lock_by_ptr(&sma
->sem_perm
);
188 ipc_unlock(&(sma
)->sem_perm
);
191 static inline void sem_rmid(struct ipc_namespace
*ns
, struct sem_array
*s
)
193 ipc_rmid(&sem_ids(ns
), &s
->sem_perm
);
197 * Lockless wakeup algorithm:
198 * Without the check/retry algorithm a lockless wakeup is possible:
199 * - queue.status is initialized to -EINTR before blocking.
200 * - wakeup is performed by
201 * * unlinking the queue entry from sma->sem_pending
202 * * setting queue.status to IN_WAKEUP
203 * This is the notification for the blocked thread that a
204 * result value is imminent.
205 * * call wake_up_process
206 * * set queue.status to the final value.
207 * - the previously blocked thread checks queue.status:
208 * * if it's IN_WAKEUP, then it must wait until the value changes
209 * * if it's not -EINTR, then the operation was completed by
210 * update_queue. semtimedop can return queue.status without
211 * performing any operation on the sem array.
212 * * otherwise it must acquire the spinlock and check what's up.
214 * The two-stage algorithm is necessary to protect against the following
216 * - if queue.status is set after wake_up_process, then the woken up idle
217 * thread could race forward and try (and fail) to acquire sma->lock
218 * before update_queue had a chance to set queue.status
219 * - if queue.status is written before wake_up_process and if the
220 * blocked process is woken up by a signal between writing
221 * queue.status and the wake_up_process, then the woken up
222 * process could return from semtimedop and die by calling
223 * sys_exit before wake_up_process is called. Then wake_up_process
224 * will oops, because the task structure is already invalid.
225 * (yes, this happened on s390 with sysv msg).
231 * newary - Create a new semaphore set
233 * @params: ptr to the structure that contains key, semflg and nsems
235 * Called with sem_ids.rw_mutex held (as a writer)
238 static int newary(struct ipc_namespace
*ns
, struct ipc_params
*params
)
242 struct sem_array
*sma
;
244 key_t key
= params
->key
;
245 int nsems
= params
->u
.nsems
;
246 int semflg
= params
->flg
;
251 if (ns
->used_sems
+ nsems
> ns
->sc_semmns
)
254 size
= sizeof (*sma
) + nsems
* sizeof (struct sem
);
255 sma
= ipc_rcu_alloc(size
);
259 memset (sma
, 0, size
);
261 sma
->sem_perm
.mode
= (semflg
& S_IRWXUGO
);
262 sma
->sem_perm
.key
= key
;
264 sma
->sem_perm
.security
= NULL
;
265 retval
= security_sem_alloc(sma
);
271 id
= ipc_addid(&sem_ids(ns
), &sma
->sem_perm
, ns
->sc_semmni
);
273 security_sem_free(sma
);
277 ns
->used_sems
+= nsems
;
279 sma
->sem_base
= (struct sem
*) &sma
[1];
281 for (i
= 0; i
< nsems
; i
++)
282 INIT_LIST_HEAD(&sma
->sem_base
[i
].sem_pending
);
284 sma
->complex_count
= 0;
285 INIT_LIST_HEAD(&sma
->sem_pending
);
286 INIT_LIST_HEAD(&sma
->list_id
);
287 sma
->sem_nsems
= nsems
;
288 sma
->sem_ctime
= get_seconds();
291 return sma
->sem_perm
.id
;
296 * Called with sem_ids.rw_mutex and ipcp locked.
298 static inline int sem_security(struct kern_ipc_perm
*ipcp
, int semflg
)
300 struct sem_array
*sma
;
302 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
303 return security_sem_associate(sma
, semflg
);
307 * Called with sem_ids.rw_mutex and ipcp locked.
309 static inline int sem_more_checks(struct kern_ipc_perm
*ipcp
,
310 struct ipc_params
*params
)
312 struct sem_array
*sma
;
314 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
315 if (params
->u
.nsems
> sma
->sem_nsems
)
321 SYSCALL_DEFINE3(semget
, key_t
, key
, int, nsems
, int, semflg
)
323 struct ipc_namespace
*ns
;
324 struct ipc_ops sem_ops
;
325 struct ipc_params sem_params
;
327 ns
= current
->nsproxy
->ipc_ns
;
329 if (nsems
< 0 || nsems
> ns
->sc_semmsl
)
332 sem_ops
.getnew
= newary
;
333 sem_ops
.associate
= sem_security
;
334 sem_ops
.more_checks
= sem_more_checks
;
336 sem_params
.key
= key
;
337 sem_params
.flg
= semflg
;
338 sem_params
.u
.nsems
= nsems
;
340 return ipcget(ns
, &sem_ids(ns
), &sem_ops
, &sem_params
);
344 * Determine whether a sequence of semaphore operations would succeed
345 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
348 static int try_atomic_semop (struct sem_array
* sma
, struct sembuf
* sops
,
349 int nsops
, struct sem_undo
*un
, int pid
)
355 for (sop
= sops
; sop
< sops
+ nsops
; sop
++) {
356 curr
= sma
->sem_base
+ sop
->sem_num
;
357 sem_op
= sop
->sem_op
;
358 result
= curr
->semval
;
360 if (!sem_op
&& result
)
368 if (sop
->sem_flg
& SEM_UNDO
) {
369 int undo
= un
->semadj
[sop
->sem_num
] - sem_op
;
371 * Exceeding the undo range is an error.
373 if (undo
< (-SEMAEM
- 1) || undo
> SEMAEM
)
376 curr
->semval
= result
;
380 while (sop
>= sops
) {
381 sma
->sem_base
[sop
->sem_num
].sempid
= pid
;
382 if (sop
->sem_flg
& SEM_UNDO
)
383 un
->semadj
[sop
->sem_num
] -= sop
->sem_op
;
394 if (sop
->sem_flg
& IPC_NOWAIT
)
401 while (sop
>= sops
) {
402 sma
->sem_base
[sop
->sem_num
].semval
-= sop
->sem_op
;
409 /** wake_up_sem_queue_prepare(q, error): Prepare wake-up
410 * @q: queue entry that must be signaled
411 * @error: Error value for the signal
413 * Prepare the wake-up of the queue entry q.
415 static void wake_up_sem_queue_prepare(struct list_head
*pt
,
416 struct sem_queue
*q
, int error
)
418 if (list_empty(pt
)) {
420 * Hold preempt off so that we don't get preempted and have the
421 * wakee busy-wait until we're scheduled back on.
425 q
->status
= IN_WAKEUP
;
428 list_add_tail(&q
->simple_list
, pt
);
432 * wake_up_sem_queue_do(pt) - do the actual wake-up
433 * @pt: list of tasks to be woken up
435 * Do the actual wake-up.
436 * The function is called without any locks held, thus the semaphore array
437 * could be destroyed already and the tasks can disappear as soon as the
438 * status is set to the actual return code.
440 static void wake_up_sem_queue_do(struct list_head
*pt
)
442 struct sem_queue
*q
, *t
;
445 did_something
= !list_empty(pt
);
446 list_for_each_entry_safe(q
, t
, pt
, simple_list
) {
447 wake_up_process(q
->sleeper
);
448 /* q can disappear immediately after writing q->status. */
456 static void unlink_queue(struct sem_array
*sma
, struct sem_queue
*q
)
460 list_del(&q
->simple_list
);
462 sma
->complex_count
--;
465 /** check_restart(sma, q)
466 * @sma: semaphore array
467 * @q: the operation that just completed
469 * update_queue is O(N^2) when it restarts scanning the whole queue of
470 * waiting operations. Therefore this function checks if the restart is
471 * really necessary. It is called after a previously waiting operation
474 static int check_restart(struct sem_array
*sma
, struct sem_queue
*q
)
479 /* if the operation didn't modify the array, then no restart */
483 /* pending complex operations are too difficult to analyse */
484 if (sma
->complex_count
)
487 /* we were a sleeping complex operation. Too difficult */
491 curr
= sma
->sem_base
+ q
->sops
[0].sem_num
;
493 /* No-one waits on this queue */
494 if (list_empty(&curr
->sem_pending
))
497 /* the new semaphore value */
499 /* It is impossible that someone waits for the new value:
500 * - q is a previously sleeping simple operation that
501 * altered the array. It must be a decrement, because
502 * simple increments never sleep.
503 * - The value is not 0, thus wait-for-zero won't proceed.
504 * - If there are older (higher priority) decrements
505 * in the queue, then they have observed the original
506 * semval value and couldn't proceed. The operation
507 * decremented to value - thus they won't proceed either.
509 BUG_ON(q
->sops
[0].sem_op
>= 0);
513 * semval is 0. Check if there are wait-for-zero semops.
514 * They must be the first entries in the per-semaphore simple queue
516 h
= list_first_entry(&curr
->sem_pending
, struct sem_queue
, simple_list
);
517 BUG_ON(h
->nsops
!= 1);
518 BUG_ON(h
->sops
[0].sem_num
!= q
->sops
[0].sem_num
);
520 /* Yes, there is a wait-for-zero semop. Restart */
521 if (h
->sops
[0].sem_op
== 0)
524 /* Again - no-one is waiting for the new value. */
530 * update_queue(sma, semnum): Look for tasks that can be completed.
531 * @sma: semaphore array.
532 * @semnum: semaphore that was modified.
533 * @pt: list head for the tasks that must be woken up.
535 * update_queue must be called after a semaphore in a semaphore array
536 * was modified. If multiple semaphore were modified, then @semnum
538 * The tasks that must be woken up are added to @pt. The return code
539 * is stored in q->pid.
540 * The function return 1 if at least one semop was completed successfully.
542 static int update_queue(struct sem_array
*sma
, int semnum
, struct list_head
*pt
)
545 struct list_head
*walk
;
546 struct list_head
*pending_list
;
548 int semop_completed
= 0;
550 /* if there are complex operations around, then knowing the semaphore
551 * that was modified doesn't help us. Assume that multiple semaphores
554 if (sma
->complex_count
)
558 pending_list
= &sma
->sem_pending
;
559 offset
= offsetof(struct sem_queue
, list
);
561 pending_list
= &sma
->sem_base
[semnum
].sem_pending
;
562 offset
= offsetof(struct sem_queue
, simple_list
);
566 walk
= pending_list
->next
;
567 while (walk
!= pending_list
) {
570 q
= (struct sem_queue
*)((char *)walk
- offset
);
573 /* If we are scanning the single sop, per-semaphore list of
574 * one semaphore and that semaphore is 0, then it is not
575 * necessary to scan the "alter" entries: simple increments
576 * that affect only one entry succeed immediately and cannot
577 * be in the per semaphore pending queue, and decrements
578 * cannot be successful if the value is already 0.
580 if (semnum
!= -1 && sma
->sem_base
[semnum
].semval
== 0 &&
584 error
= try_atomic_semop(sma
, q
->sops
, q
->nsops
,
587 /* Does q->sleeper still need to sleep? */
591 unlink_queue(sma
, q
);
597 restart
= check_restart(sma
, q
);
600 wake_up_sem_queue_prepare(pt
, q
, error
);
604 return semop_completed
;
608 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
609 * @sma: semaphore array
610 * @sops: operations that were performed
611 * @nsops: number of operations
612 * @otime: force setting otime
613 * @pt: list head of the tasks that must be woken up.
615 * do_smart_update() does the required called to update_queue, based on the
616 * actual changes that were performed on the semaphore array.
617 * Note that the function does not do the actual wake-up: the caller is
618 * responsible for calling wake_up_sem_queue_do(@pt).
619 * It is safe to perform this call after dropping all locks.
621 static void do_smart_update(struct sem_array
*sma
, struct sembuf
*sops
, int nsops
,
622 int otime
, struct list_head
*pt
)
626 if (sma
->complex_count
|| sops
== NULL
) {
627 if (update_queue(sma
, -1, pt
))
632 for (i
= 0; i
< nsops
; i
++) {
633 if (sops
[i
].sem_op
> 0 ||
634 (sops
[i
].sem_op
< 0 &&
635 sma
->sem_base
[sops
[i
].sem_num
].semval
== 0))
636 if (update_queue(sma
, sops
[i
].sem_num
, pt
))
641 sma
->sem_otime
= get_seconds();
645 /* The following counts are associated to each semaphore:
646 * semncnt number of tasks waiting on semval being nonzero
647 * semzcnt number of tasks waiting on semval being zero
648 * This model assumes that a task waits on exactly one semaphore.
649 * Since semaphore operations are to be performed atomically, tasks actually
650 * wait on a whole sequence of semaphores simultaneously.
651 * The counts we return here are a rough approximation, but still
652 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
654 static int count_semncnt (struct sem_array
* sma
, ushort semnum
)
657 struct sem_queue
* q
;
660 list_for_each_entry(q
, &sma
->sem_pending
, list
) {
661 struct sembuf
* sops
= q
->sops
;
662 int nsops
= q
->nsops
;
664 for (i
= 0; i
< nsops
; i
++)
665 if (sops
[i
].sem_num
== semnum
666 && (sops
[i
].sem_op
< 0)
667 && !(sops
[i
].sem_flg
& IPC_NOWAIT
))
673 static int count_semzcnt (struct sem_array
* sma
, ushort semnum
)
676 struct sem_queue
* q
;
679 list_for_each_entry(q
, &sma
->sem_pending
, list
) {
680 struct sembuf
* sops
= q
->sops
;
681 int nsops
= q
->nsops
;
683 for (i
= 0; i
< nsops
; i
++)
684 if (sops
[i
].sem_num
== semnum
685 && (sops
[i
].sem_op
== 0)
686 && !(sops
[i
].sem_flg
& IPC_NOWAIT
))
692 /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
693 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
694 * remains locked on exit.
696 static void freeary(struct ipc_namespace
*ns
, struct kern_ipc_perm
*ipcp
)
698 struct sem_undo
*un
, *tu
;
699 struct sem_queue
*q
, *tq
;
700 struct sem_array
*sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
701 struct list_head tasks
;
703 /* Free the existing undo structures for this semaphore set. */
704 assert_spin_locked(&sma
->sem_perm
.lock
);
705 list_for_each_entry_safe(un
, tu
, &sma
->list_id
, list_id
) {
706 list_del(&un
->list_id
);
707 spin_lock(&un
->ulp
->lock
);
709 list_del_rcu(&un
->list_proc
);
710 spin_unlock(&un
->ulp
->lock
);
714 /* Wake up all pending processes and let them fail with EIDRM. */
715 INIT_LIST_HEAD(&tasks
);
716 list_for_each_entry_safe(q
, tq
, &sma
->sem_pending
, list
) {
717 unlink_queue(sma
, q
);
718 wake_up_sem_queue_prepare(&tasks
, q
, -EIDRM
);
721 /* Remove the semaphore set from the IDR */
725 wake_up_sem_queue_do(&tasks
);
726 ns
->used_sems
-= sma
->sem_nsems
;
727 security_sem_free(sma
);
731 static unsigned long copy_semid_to_user(void __user
*buf
, struct semid64_ds
*in
, int version
)
735 return copy_to_user(buf
, in
, sizeof(*in
));
740 memset(&out
, 0, sizeof(out
));
742 ipc64_perm_to_ipc_perm(&in
->sem_perm
, &out
.sem_perm
);
744 out
.sem_otime
= in
->sem_otime
;
745 out
.sem_ctime
= in
->sem_ctime
;
746 out
.sem_nsems
= in
->sem_nsems
;
748 return copy_to_user(buf
, &out
, sizeof(out
));
755 static int semctl_nolock(struct ipc_namespace
*ns
, int semid
,
756 int cmd
, int version
, union semun arg
)
759 struct sem_array
*sma
;
765 struct seminfo seminfo
;
768 err
= security_sem_semctl(NULL
, cmd
);
772 memset(&seminfo
,0,sizeof(seminfo
));
773 seminfo
.semmni
= ns
->sc_semmni
;
774 seminfo
.semmns
= ns
->sc_semmns
;
775 seminfo
.semmsl
= ns
->sc_semmsl
;
776 seminfo
.semopm
= ns
->sc_semopm
;
777 seminfo
.semvmx
= SEMVMX
;
778 seminfo
.semmnu
= SEMMNU
;
779 seminfo
.semmap
= SEMMAP
;
780 seminfo
.semume
= SEMUME
;
781 down_read(&sem_ids(ns
).rw_mutex
);
782 if (cmd
== SEM_INFO
) {
783 seminfo
.semusz
= sem_ids(ns
).in_use
;
784 seminfo
.semaem
= ns
->used_sems
;
786 seminfo
.semusz
= SEMUSZ
;
787 seminfo
.semaem
= SEMAEM
;
789 max_id
= ipc_get_maxid(&sem_ids(ns
));
790 up_read(&sem_ids(ns
).rw_mutex
);
791 if (copy_to_user (arg
.__buf
, &seminfo
, sizeof(struct seminfo
)))
793 return (max_id
< 0) ? 0: max_id
;
798 struct semid64_ds tbuf
;
801 if (cmd
== SEM_STAT
) {
802 sma
= sem_lock(ns
, semid
);
805 id
= sma
->sem_perm
.id
;
807 sma
= sem_lock_check(ns
, semid
);
814 if (ipcperms(ns
, &sma
->sem_perm
, S_IRUGO
))
817 err
= security_sem_semctl(sma
, cmd
);
821 memset(&tbuf
, 0, sizeof(tbuf
));
823 kernel_to_ipc64_perm(&sma
->sem_perm
, &tbuf
.sem_perm
);
824 tbuf
.sem_otime
= sma
->sem_otime
;
825 tbuf
.sem_ctime
= sma
->sem_ctime
;
826 tbuf
.sem_nsems
= sma
->sem_nsems
;
828 if (copy_semid_to_user (arg
.buf
, &tbuf
, version
))
840 static int semctl_main(struct ipc_namespace
*ns
, int semid
, int semnum
,
841 int cmd
, int version
, union semun arg
)
843 struct sem_array
*sma
;
846 ushort fast_sem_io
[SEMMSL_FAST
];
847 ushort
* sem_io
= fast_sem_io
;
849 struct list_head tasks
;
851 sma
= sem_lock_check(ns
, semid
);
855 INIT_LIST_HEAD(&tasks
);
856 nsems
= sma
->sem_nsems
;
859 if (ipcperms(ns
, &sma
->sem_perm
,
860 (cmd
== SETVAL
|| cmd
== SETALL
) ? S_IWUGO
: S_IRUGO
))
863 err
= security_sem_semctl(sma
, cmd
);
871 ushort __user
*array
= arg
.array
;
874 if(nsems
> SEMMSL_FAST
) {
875 sem_getref_and_unlock(sma
);
877 sem_io
= ipc_alloc(sizeof(ushort
)*nsems
);
883 sem_lock_and_putref(sma
);
884 if (sma
->sem_perm
.deleted
) {
891 for (i
= 0; i
< sma
->sem_nsems
; i
++)
892 sem_io
[i
] = sma
->sem_base
[i
].semval
;
895 if(copy_to_user(array
, sem_io
, nsems
*sizeof(ushort
)))
904 sem_getref_and_unlock(sma
);
906 if(nsems
> SEMMSL_FAST
) {
907 sem_io
= ipc_alloc(sizeof(ushort
)*nsems
);
914 if (copy_from_user (sem_io
, arg
.array
, nsems
*sizeof(ushort
))) {
920 for (i
= 0; i
< nsems
; i
++) {
921 if (sem_io
[i
] > SEMVMX
) {
927 sem_lock_and_putref(sma
);
928 if (sma
->sem_perm
.deleted
) {
934 for (i
= 0; i
< nsems
; i
++)
935 sma
->sem_base
[i
].semval
= sem_io
[i
];
937 assert_spin_locked(&sma
->sem_perm
.lock
);
938 list_for_each_entry(un
, &sma
->list_id
, list_id
) {
939 for (i
= 0; i
< nsems
; i
++)
942 sma
->sem_ctime
= get_seconds();
943 /* maybe some queued-up processes were waiting for this */
944 do_smart_update(sma
, NULL
, 0, 0, &tasks
);
948 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
951 if(semnum
< 0 || semnum
>= nsems
)
954 curr
= &sma
->sem_base
[semnum
];
964 err
= count_semncnt(sma
,semnum
);
967 err
= count_semzcnt(sma
,semnum
);
975 if (val
> SEMVMX
|| val
< 0)
978 assert_spin_locked(&sma
->sem_perm
.lock
);
979 list_for_each_entry(un
, &sma
->list_id
, list_id
)
980 un
->semadj
[semnum
] = 0;
983 curr
->sempid
= task_tgid_vnr(current
);
984 sma
->sem_ctime
= get_seconds();
985 /* maybe some queued-up processes were waiting for this */
986 do_smart_update(sma
, NULL
, 0, 0, &tasks
);
993 wake_up_sem_queue_do(&tasks
);
996 if(sem_io
!= fast_sem_io
)
997 ipc_free(sem_io
, sizeof(ushort
)*nsems
);
1001 static inline unsigned long
1002 copy_semid_from_user(struct semid64_ds
*out
, void __user
*buf
, int version
)
1006 if (copy_from_user(out
, buf
, sizeof(*out
)))
1011 struct semid_ds tbuf_old
;
1013 if(copy_from_user(&tbuf_old
, buf
, sizeof(tbuf_old
)))
1016 out
->sem_perm
.uid
= tbuf_old
.sem_perm
.uid
;
1017 out
->sem_perm
.gid
= tbuf_old
.sem_perm
.gid
;
1018 out
->sem_perm
.mode
= tbuf_old
.sem_perm
.mode
;
1028 * This function handles some semctl commands which require the rw_mutex
1029 * to be held in write mode.
1030 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1032 static int semctl_down(struct ipc_namespace
*ns
, int semid
,
1033 int cmd
, int version
, union semun arg
)
1035 struct sem_array
*sma
;
1037 struct semid64_ds semid64
;
1038 struct kern_ipc_perm
*ipcp
;
1040 if(cmd
== IPC_SET
) {
1041 if (copy_semid_from_user(&semid64
, arg
.buf
, version
))
1045 ipcp
= ipcctl_pre_down(ns
, &sem_ids(ns
), semid
, cmd
,
1046 &semid64
.sem_perm
, 0);
1048 return PTR_ERR(ipcp
);
1050 sma
= container_of(ipcp
, struct sem_array
, sem_perm
);
1052 err
= security_sem_semctl(sma
, cmd
);
1061 ipc_update_perm(&semid64
.sem_perm
, ipcp
);
1062 sma
->sem_ctime
= get_seconds();
1071 up_write(&sem_ids(ns
).rw_mutex
);
1075 SYSCALL_DEFINE(semctl
)(int semid
, int semnum
, int cmd
, union semun arg
)
1079 struct ipc_namespace
*ns
;
1084 version
= ipc_parse_version(&cmd
);
1085 ns
= current
->nsproxy
->ipc_ns
;
1092 err
= semctl_nolock(ns
, semid
, cmd
, version
, arg
);
1101 err
= semctl_main(ns
,semid
,semnum
,cmd
,version
,arg
);
1105 err
= semctl_down(ns
, semid
, cmd
, version
, arg
);
1111 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1112 asmlinkage
long SyS_semctl(int semid
, int semnum
, int cmd
, union semun arg
)
1114 return SYSC_semctl((int) semid
, (int) semnum
, (int) cmd
, arg
);
1116 SYSCALL_ALIAS(sys_semctl
, SyS_semctl
);
1119 /* If the task doesn't already have a undo_list, then allocate one
1120 * here. We guarantee there is only one thread using this undo list,
1121 * and current is THE ONE
1123 * If this allocation and assignment succeeds, but later
1124 * portions of this code fail, there is no need to free the sem_undo_list.
1125 * Just let it stay associated with the task, and it'll be freed later
1128 * This can block, so callers must hold no locks.
1130 static inline int get_undo_list(struct sem_undo_list
**undo_listp
)
1132 struct sem_undo_list
*undo_list
;
1134 undo_list
= current
->sysvsem
.undo_list
;
1136 undo_list
= kzalloc(sizeof(*undo_list
), GFP_KERNEL
);
1137 if (undo_list
== NULL
)
1139 spin_lock_init(&undo_list
->lock
);
1140 atomic_set(&undo_list
->refcnt
, 1);
1141 INIT_LIST_HEAD(&undo_list
->list_proc
);
1143 current
->sysvsem
.undo_list
= undo_list
;
1145 *undo_listp
= undo_list
;
1149 static struct sem_undo
*__lookup_undo(struct sem_undo_list
*ulp
, int semid
)
1151 struct sem_undo
*un
;
1153 list_for_each_entry_rcu(un
, &ulp
->list_proc
, list_proc
) {
1154 if (un
->semid
== semid
)
1160 static struct sem_undo
*lookup_undo(struct sem_undo_list
*ulp
, int semid
)
1162 struct sem_undo
*un
;
1164 assert_spin_locked(&ulp
->lock
);
1166 un
= __lookup_undo(ulp
, semid
);
1168 list_del_rcu(&un
->list_proc
);
1169 list_add_rcu(&un
->list_proc
, &ulp
->list_proc
);
1175 * find_alloc_undo - Lookup (and if not present create) undo array
1177 * @semid: semaphore array id
1179 * The function looks up (and if not present creates) the undo structure.
1180 * The size of the undo structure depends on the size of the semaphore
1181 * array, thus the alloc path is not that straightforward.
1182 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1183 * performs a rcu_read_lock().
1185 static struct sem_undo
*find_alloc_undo(struct ipc_namespace
*ns
, int semid
)
1187 struct sem_array
*sma
;
1188 struct sem_undo_list
*ulp
;
1189 struct sem_undo
*un
, *new;
1193 error
= get_undo_list(&ulp
);
1195 return ERR_PTR(error
);
1198 spin_lock(&ulp
->lock
);
1199 un
= lookup_undo(ulp
, semid
);
1200 spin_unlock(&ulp
->lock
);
1201 if (likely(un
!=NULL
))
1205 /* no undo structure around - allocate one. */
1206 /* step 1: figure out the size of the semaphore array */
1207 sma
= sem_lock_check(ns
, semid
);
1209 return ERR_CAST(sma
);
1211 nsems
= sma
->sem_nsems
;
1212 sem_getref_and_unlock(sma
);
1214 /* step 2: allocate new undo structure */
1215 new = kzalloc(sizeof(struct sem_undo
) + sizeof(short)*nsems
, GFP_KERNEL
);
1218 return ERR_PTR(-ENOMEM
);
1221 /* step 3: Acquire the lock on semaphore array */
1222 sem_lock_and_putref(sma
);
1223 if (sma
->sem_perm
.deleted
) {
1226 un
= ERR_PTR(-EIDRM
);
1229 spin_lock(&ulp
->lock
);
1232 * step 4: check for races: did someone else allocate the undo struct?
1234 un
= lookup_undo(ulp
, semid
);
1239 /* step 5: initialize & link new undo structure */
1240 new->semadj
= (short *) &new[1];
1243 assert_spin_locked(&ulp
->lock
);
1244 list_add_rcu(&new->list_proc
, &ulp
->list_proc
);
1245 assert_spin_locked(&sma
->sem_perm
.lock
);
1246 list_add(&new->list_id
, &sma
->list_id
);
1250 spin_unlock(&ulp
->lock
);
1259 * get_queue_result - Retrieve the result code from sem_queue
1260 * @q: Pointer to queue structure
1262 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1263 * q->status, then we must loop until the value is replaced with the final
1264 * value: This may happen if a task is woken up by an unrelated event (e.g.
1265 * signal) and in parallel the task is woken up by another task because it got
1266 * the requested semaphores.
1268 * The function can be called with or without holding the semaphore spinlock.
1270 static int get_queue_result(struct sem_queue
*q
)
1275 while (unlikely(error
== IN_WAKEUP
)) {
1284 SYSCALL_DEFINE4(semtimedop
, int, semid
, struct sembuf __user
*, tsops
,
1285 unsigned, nsops
, const struct timespec __user
*, timeout
)
1287 int error
= -EINVAL
;
1288 struct sem_array
*sma
;
1289 struct sembuf fast_sops
[SEMOPM_FAST
];
1290 struct sembuf
* sops
= fast_sops
, *sop
;
1291 struct sem_undo
*un
;
1292 int undos
= 0, alter
= 0, max
;
1293 struct sem_queue queue
;
1294 unsigned long jiffies_left
= 0;
1295 struct ipc_namespace
*ns
;
1296 struct list_head tasks
;
1298 ns
= current
->nsproxy
->ipc_ns
;
1300 if (nsops
< 1 || semid
< 0)
1302 if (nsops
> ns
->sc_semopm
)
1304 if(nsops
> SEMOPM_FAST
) {
1305 sops
= kmalloc(sizeof(*sops
)*nsops
,GFP_KERNEL
);
1309 if (copy_from_user (sops
, tsops
, nsops
* sizeof(*tsops
))) {
1314 struct timespec _timeout
;
1315 if (copy_from_user(&_timeout
, timeout
, sizeof(*timeout
))) {
1319 if (_timeout
.tv_sec
< 0 || _timeout
.tv_nsec
< 0 ||
1320 _timeout
.tv_nsec
>= 1000000000L) {
1324 jiffies_left
= timespec_to_jiffies(&_timeout
);
1327 for (sop
= sops
; sop
< sops
+ nsops
; sop
++) {
1328 if (sop
->sem_num
>= max
)
1330 if (sop
->sem_flg
& SEM_UNDO
)
1332 if (sop
->sem_op
!= 0)
1337 un
= find_alloc_undo(ns
, semid
);
1339 error
= PTR_ERR(un
);
1345 INIT_LIST_HEAD(&tasks
);
1347 sma
= sem_lock_check(ns
, semid
);
1351 error
= PTR_ERR(sma
);
1356 * semid identifiers are not unique - find_alloc_undo may have
1357 * allocated an undo structure, it was invalidated by an RMID
1358 * and now a new array with received the same id. Check and fail.
1359 * This case can be detected checking un->semid. The existence of
1360 * "un" itself is guaranteed by rcu.
1364 if (un
->semid
== -1) {
1366 goto out_unlock_free
;
1369 * rcu lock can be released, "un" cannot disappear:
1370 * - sem_lock is acquired, thus IPC_RMID is
1372 * - exit_sem is impossible, it always operates on
1373 * current (or a dead task).
1381 if (max
>= sma
->sem_nsems
)
1382 goto out_unlock_free
;
1385 if (ipcperms(ns
, &sma
->sem_perm
, alter
? S_IWUGO
: S_IRUGO
))
1386 goto out_unlock_free
;
1388 error
= security_sem_semop(sma
, sops
, nsops
, alter
);
1390 goto out_unlock_free
;
1392 error
= try_atomic_semop (sma
, sops
, nsops
, un
, task_tgid_vnr(current
));
1394 if (alter
&& error
== 0)
1395 do_smart_update(sma
, sops
, nsops
, 1, &tasks
);
1397 goto out_unlock_free
;
1400 /* We need to sleep on this operation, so we put the current
1401 * task into the pending queue and go to sleep.
1405 queue
.nsops
= nsops
;
1407 queue
.pid
= task_tgid_vnr(current
);
1408 queue
.alter
= alter
;
1410 list_add_tail(&queue
.list
, &sma
->sem_pending
);
1412 list_add(&queue
.list
, &sma
->sem_pending
);
1416 curr
= &sma
->sem_base
[sops
->sem_num
];
1419 list_add_tail(&queue
.simple_list
, &curr
->sem_pending
);
1421 list_add(&queue
.simple_list
, &curr
->sem_pending
);
1423 INIT_LIST_HEAD(&queue
.simple_list
);
1424 sma
->complex_count
++;
1427 queue
.status
= -EINTR
;
1428 queue
.sleeper
= current
;
1429 current
->state
= TASK_INTERRUPTIBLE
;
1433 jiffies_left
= schedule_timeout(jiffies_left
);
1437 error
= get_queue_result(&queue
);
1439 if (error
!= -EINTR
) {
1440 /* fast path: update_queue already obtained all requested
1442 * Perform a smp_mb(): User space could assume that semop()
1443 * is a memory barrier: Without the mb(), the cpu could
1444 * speculatively read in user space stale data that was
1445 * overwritten by the previous owner of the semaphore.
1452 sma
= sem_lock(ns
, semid
);
1458 error
= get_queue_result(&queue
);
1461 * If queue.status != -EINTR we are woken up by another process
1464 if (error
!= -EINTR
) {
1465 goto out_unlock_free
;
1469 * If an interrupt occurred we have to clean up the queue
1471 if (timeout
&& jiffies_left
== 0)
1473 unlink_queue(sma
, &queue
);
1478 wake_up_sem_queue_do(&tasks
);
1480 if(sops
!= fast_sops
)
1485 SYSCALL_DEFINE3(semop
, int, semid
, struct sembuf __user
*, tsops
,
1488 return sys_semtimedop(semid
, tsops
, nsops
, NULL
);
1491 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1492 * parent and child tasks.
1495 int copy_semundo(unsigned long clone_flags
, struct task_struct
*tsk
)
1497 struct sem_undo_list
*undo_list
;
1500 if (clone_flags
& CLONE_SYSVSEM
) {
1501 error
= get_undo_list(&undo_list
);
1504 atomic_inc(&undo_list
->refcnt
);
1505 tsk
->sysvsem
.undo_list
= undo_list
;
1507 tsk
->sysvsem
.undo_list
= NULL
;
1513 * add semadj values to semaphores, free undo structures.
1514 * undo structures are not freed when semaphore arrays are destroyed
1515 * so some of them may be out of date.
1516 * IMPLEMENTATION NOTE: There is some confusion over whether the
1517 * set of adjustments that needs to be done should be done in an atomic
1518 * manner or not. That is, if we are attempting to decrement the semval
1519 * should we queue up and wait until we can do so legally?
1520 * The original implementation attempted to do this (queue and wait).
1521 * The current implementation does not do so. The POSIX standard
1522 * and SVID should be consulted to determine what behavior is mandated.
1524 void exit_sem(struct task_struct
*tsk
)
1526 struct sem_undo_list
*ulp
;
1528 ulp
= tsk
->sysvsem
.undo_list
;
1531 tsk
->sysvsem
.undo_list
= NULL
;
1533 if (!atomic_dec_and_test(&ulp
->refcnt
))
1537 struct sem_array
*sma
;
1538 struct sem_undo
*un
;
1539 struct list_head tasks
;
1544 un
= list_entry_rcu(ulp
->list_proc
.next
,
1545 struct sem_undo
, list_proc
);
1546 if (&un
->list_proc
== &ulp
->list_proc
)
1555 sma
= sem_lock_check(tsk
->nsproxy
->ipc_ns
, un
->semid
);
1557 /* exit_sem raced with IPC_RMID, nothing to do */
1561 un
= __lookup_undo(ulp
, semid
);
1563 /* exit_sem raced with IPC_RMID+semget() that created
1564 * exactly the same semid. Nothing to do.
1570 /* remove un from the linked lists */
1571 assert_spin_locked(&sma
->sem_perm
.lock
);
1572 list_del(&un
->list_id
);
1574 spin_lock(&ulp
->lock
);
1575 list_del_rcu(&un
->list_proc
);
1576 spin_unlock(&ulp
->lock
);
1578 /* perform adjustments registered in un */
1579 for (i
= 0; i
< sma
->sem_nsems
; i
++) {
1580 struct sem
* semaphore
= &sma
->sem_base
[i
];
1581 if (un
->semadj
[i
]) {
1582 semaphore
->semval
+= un
->semadj
[i
];
1584 * Range checks of the new semaphore value,
1585 * not defined by sus:
1586 * - Some unices ignore the undo entirely
1587 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1588 * - some cap the value (e.g. FreeBSD caps
1589 * at 0, but doesn't enforce SEMVMX)
1591 * Linux caps the semaphore value, both at 0
1594 * Manfred <manfred@colorfullife.com>
1596 if (semaphore
->semval
< 0)
1597 semaphore
->semval
= 0;
1598 if (semaphore
->semval
> SEMVMX
)
1599 semaphore
->semval
= SEMVMX
;
1600 semaphore
->sempid
= task_tgid_vnr(current
);
1603 /* maybe some queued-up processes were waiting for this */
1604 INIT_LIST_HEAD(&tasks
);
1605 do_smart_update(sma
, NULL
, 0, 1, &tasks
);
1607 wake_up_sem_queue_do(&tasks
);
1614 #ifdef CONFIG_PROC_FS
1615 static int sysvipc_sem_proc_show(struct seq_file
*s
, void *it
)
1617 struct sem_array
*sma
= it
;
1619 return seq_printf(s
,
1620 "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",