3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
6 * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
7 * This code underwent a massive rewrite in order to solve some problems
8 * with the original code. In particular the original code failed to
9 * wake up processes that were waiting for semval to go to 0 if the
10 * value went to 0 and was then incremented rapidly enough. In solving
11 * this problem I have also modified the implementation so that it
12 * processes pending operations in a FIFO manner, thus give a guarantee
13 * that processes waiting for a lock on the semaphore won't starve
14 * unless another locking process fails to unlock.
15 * In addition the following two changes in behavior have been introduced:
16 * - The original implementation of semop returned the value
17 * last semaphore element examined on success. This does not
18 * match the manual page specifications, and effectively
19 * allows the user to read the semaphore even if they do not
20 * have read permissions. The implementation now returns 0
21 * on success as stated in the manual page.
22 * - There is some confusion over whether the set of undo adjustments
23 * to be performed at exit should be done in an atomic manner.
24 * That is, if we are attempting to decrement the semval should we queue
25 * up and wait until we can do so legally?
26 * The original implementation attempted to do this.
27 * The current implementation does not do so. This is because I don't
28 * think it is the right thing (TM) to do, and because I couldn't
29 * see a clean way to get the old behavior with the new design.
30 * The POSIX standard and SVID should be consulted to determine
31 * what behavior is mandated.
33 * Further notes on refinement (Christoph Rohland, December 1998):
34 * - The POSIX standard says, that the undo adjustments simply should
35 * redo. So the current implementation is o.K.
36 * - The previous code had two flaws:
37 * 1) It actively gave the semaphore to the next waiting process
38 * sleeping on the semaphore. Since this process did not have the
39 * cpu this led to many unnecessary context switches and bad
40 * performance. Now we only check which process should be able to
41 * get the semaphore and if this process wants to reduce some
42 * semaphore value we simply wake it up without doing the
43 * operation. So it has to try to get it later. Thus e.g. the
44 * running process may reacquire the semaphore during the current
45 * time slice. If it only waits for zero or increases the semaphore,
46 * we do the operation in advance and wake it up.
47 * 2) It did not wake up all zero waiting processes. We try to do
48 * better but only get the semops right which only wait for zero or
49 * increase. If there are decrement operations in the operations
50 * array we do the same as before.
52 * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
53 * check/retry algorithm for waking up blocked processes as the new scheduler
54 * is better at handling thread switch than the old one.
56 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
58 * SMP-threaded, sysctl's added
59 * (c) 1999 Manfred Spraul <manfreds@colorfullife.com>
60 * Enforced range limit on SEM_UNDO
61 * (c) 2001 Red Hat Inc <alan@redhat.com>
63 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
66 #include <linux/config.h>
67 #include <linux/slab.h>
68 #include <linux/spinlock.h>
69 #include <linux/init.h>
70 #include <linux/proc_fs.h>
71 #include <linux/time.h>
72 #include <linux/smp_lock.h>
73 #include <linux/security.h>
74 #include <linux/syscalls.h>
75 #include <linux/audit.h>
76 #include <linux/seq_file.h>
77 #include <asm/uaccess.h>
81 #define sem_lock(id) ((struct sem_array*)ipc_lock(&sem_ids,id))
82 #define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
83 #define sem_rmid(id) ((struct sem_array*)ipc_rmid(&sem_ids,id))
84 #define sem_checkid(sma, semid) \
85 ipc_checkid(&sem_ids,&sma->sem_perm,semid)
86 #define sem_buildid(id, seq) \
87 ipc_buildid(&sem_ids, id, seq)
88 static struct ipc_ids sem_ids;
90 static int newary (key_t, int, int);
91 static void freeary (struct sem_array *sma, int id);
93 static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
96 #define SEMMSL_FAST 256 /* 512 bytes on stack */
97 #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
100 * linked list protection:
102 * sem_array.sem_pending{,last},
103 * sem_array.sem_undo: sem_lock() for read/write
104 * sem_undo.proc_next: only "current" is allowed to read/write that field.
108 int sem_ctls[4] = {SEMMSL, SEMMNS, SEMOPM, SEMMNI};
109 #define sc_semmsl (sem_ctls[0])
110 #define sc_semmns (sem_ctls[1])
111 #define sc_semopm (sem_ctls[2])
112 #define sc_semmni (sem_ctls[3])
114 static int used_sems;
116 void __init sem_init (void)
119 ipc_init_ids(&sem_ids,sc_semmni);
120 ipc_init_proc_interface("sysvipc/sem",
121 " key semid perms nsems uid gid cuid cgid otime ctime\n",
123 sysvipc_sem_proc_show);
127 * Lockless wakeup algorithm:
128 * Without the check/retry algorithm a lockless wakeup is possible:
129 * - queue.status is initialized to -EINTR before blocking.
130 * - wakeup is performed by
131 * * unlinking the queue entry from sma->sem_pending
132 * * setting queue.status to IN_WAKEUP
133 * This is the notification for the blocked thread that a
134 * result value is imminent.
135 * * call wake_up_process
136 * * set queue.status to the final value.
137 * - the previously blocked thread checks queue.status:
138 * * if it's IN_WAKEUP, then it must wait until the value changes
139 * * if it's not -EINTR, then the operation was completed by
140 * update_queue. semtimedop can return queue.status without
141 * performing any operation on the semaphore array.
142 * * otherwise it must acquire the spinlock and check what's up.
144 * The two-stage algorithm is necessary to protect against the following
146 * - if queue.status is set after wake_up_process, then the woken up idle
147 * thread could race forward and try (and fail) to acquire sma->lock
148 * before update_queue had a chance to set queue.status
149 * - if queue.status is written before wake_up_process and if the
150 * blocked process is woken up by a signal between writing
151 * queue.status and the wake_up_process, then the woken up
152 * process could return from semtimedop and die by calling
153 * sys_exit before wake_up_process is called. Then wake_up_process
154 * will oops, because the task structure is already invalid.
155 * (yes, this happened on s390 with sysv msg).
160 static int newary (key_t key, int nsems, int semflg)
164 struct sem_array *sma;
169 if (used_sems + nsems > sc_semmns)
172 size = sizeof (*sma) + nsems * sizeof (struct sem);
173 sma = ipc_rcu_alloc(size);
177 memset (sma, 0, size);
179 sma->sem_perm.mode = (semflg & S_IRWXUGO);
180 sma->sem_perm.key = key;
182 sma->sem_perm.security = NULL;
183 retval = security_sem_alloc(sma);
189 id = ipc_addid(&sem_ids, &sma->sem_perm, sc_semmni);
191 security_sem_free(sma);
197 sma->sem_id = sem_buildid(id, sma->sem_perm.seq);
198 sma->sem_base = (struct sem *) &sma[1];
199 /* sma->sem_pending = NULL; */
200 sma->sem_pending_last = &sma->sem_pending;
201 /* sma->undo = NULL; */
202 sma->sem_nsems = nsems;
203 sma->sem_ctime = get_seconds();
209 asmlinkage long sys_semget (key_t key, int nsems, int semflg)
211 int id, err = -EINVAL;
212 struct sem_array *sma;
214 if (nsems < 0 || nsems > sc_semmsl)
218 if (key == IPC_PRIVATE) {
219 err = newary(key, nsems, semflg);
220 } else if ((id = ipc_findkey(&sem_ids, key)) == -1) { /* key not used */
221 if (!(semflg & IPC_CREAT))
224 err = newary(key, nsems, semflg);
225 } else if (semflg & IPC_CREAT && semflg & IPC_EXCL) {
231 if (nsems > sma->sem_nsems)
233 else if (ipcperms(&sma->sem_perm, semflg))
236 int semid = sem_buildid(id, sma->sem_perm.seq);
237 err = security_sem_associate(sma, semflg);
248 /* Manage the doubly linked list sma->sem_pending as a FIFO:
249 * insert new queue elements at the tail sma->sem_pending_last.
251 static inline void append_to_queue (struct sem_array * sma,
252 struct sem_queue * q)
254 *(q->prev = sma->sem_pending_last) = q;
255 *(sma->sem_pending_last = &q->next) = NULL;
258 static inline void prepend_to_queue (struct sem_array * sma,
259 struct sem_queue * q)
261 q->next = sma->sem_pending;
262 *(q->prev = &sma->sem_pending) = q;
264 q->next->prev = &q->next;
265 else /* sma->sem_pending_last == &sma->sem_pending */
266 sma->sem_pending_last = &q->next;
269 static inline void remove_from_queue (struct sem_array * sma,
270 struct sem_queue * q)
272 *(q->prev) = q->next;
274 q->next->prev = q->prev;
275 else /* sma->sem_pending_last == &q->next */
276 sma->sem_pending_last = q->prev;
277 q->prev = NULL; /* mark as removed */
281 * Determine whether a sequence of semaphore operations would succeed
282 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
285 static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
286 int nsops, struct sem_undo *un, int pid)
292 for (sop = sops; sop < sops + nsops; sop++) {
293 curr = sma->sem_base + sop->sem_num;
294 sem_op = sop->sem_op;
295 result = curr->semval;
297 if (!sem_op && result)
305 if (sop->sem_flg & SEM_UNDO) {
306 int undo = un->semadj[sop->sem_num] - sem_op;
308 * Exceeding the undo range is an error.
310 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
313 curr->semval = result;
317 while (sop >= sops) {
318 sma->sem_base[sop->sem_num].sempid = pid;
319 if (sop->sem_flg & SEM_UNDO)
320 un->semadj[sop->sem_num] -= sop->sem_op;
324 sma->sem_otime = get_seconds();
332 if (sop->sem_flg & IPC_NOWAIT)
339 while (sop >= sops) {
340 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
347 /* Go through the pending queue for the indicated semaphore
348 * looking for tasks that can be completed.
350 static void update_queue (struct sem_array * sma)
353 struct sem_queue * q;
355 q = sma->sem_pending;
357 error = try_atomic_semop(sma, q->sops, q->nsops,
360 /* Does q->sleeper still need to sleep? */
363 remove_from_queue(sma,q);
364 q->status = IN_WAKEUP;
366 * Continue scanning. The next operation
367 * that must be checked depends on the type of the
368 * completed operation:
369 * - if the operation modified the array, then
370 * restart from the head of the queue and
371 * check for threads that might be waiting
372 * for semaphore values to become 0.
373 * - if the operation didn't modify the array,
374 * then just continue.
377 n = sma->sem_pending;
380 wake_up_process(q->sleeper);
381 /* hands-off: q will disappear immediately after
393 /* The following counts are associated to each semaphore:
394 * semncnt number of tasks waiting on semval being nonzero
395 * semzcnt number of tasks waiting on semval being zero
396 * This model assumes that a task waits on exactly one semaphore.
397 * Since semaphore operations are to be performed atomically, tasks actually
398 * wait on a whole sequence of semaphores simultaneously.
399 * The counts we return here are a rough approximation, but still
400 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
402 static int count_semncnt (struct sem_array * sma, ushort semnum)
405 struct sem_queue * q;
408 for (q = sma->sem_pending; q; q = q->next) {
409 struct sembuf * sops = q->sops;
410 int nsops = q->nsops;
412 for (i = 0; i < nsops; i++)
413 if (sops[i].sem_num == semnum
414 && (sops[i].sem_op < 0)
415 && !(sops[i].sem_flg & IPC_NOWAIT))
420 static int count_semzcnt (struct sem_array * sma, ushort semnum)
423 struct sem_queue * q;
426 for (q = sma->sem_pending; q; q = q->next) {
427 struct sembuf * sops = q->sops;
428 int nsops = q->nsops;
430 for (i = 0; i < nsops; i++)
431 if (sops[i].sem_num == semnum
432 && (sops[i].sem_op == 0)
433 && !(sops[i].sem_flg & IPC_NOWAIT))
439 /* Free a semaphore set. freeary() is called with sem_ids.sem down and
440 * the spinlock for this semaphore set hold. sem_ids.sem remains locked
443 static void freeary (struct sem_array *sma, int id)
449 /* Invalidate the existing undo structures for this semaphore set.
450 * (They will be freed without any further action in exit_sem()
451 * or during the next semop.)
453 for (un = sma->undo; un; un = un->id_next)
456 /* Wake up all pending processes and let them fail with EIDRM. */
457 q = sma->sem_pending;
460 /* lazy remove_from_queue: we are killing the whole queue */
463 q->status = IN_WAKEUP;
464 wake_up_process(q->sleeper); /* doesn't sleep */
466 q->status = -EIDRM; /* hands-off q */
470 /* Remove the semaphore set from the ID array*/
474 used_sems -= sma->sem_nsems;
475 size = sizeof (*sma) + sma->sem_nsems * sizeof (struct sem);
476 security_sem_free(sma);
480 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
484 return copy_to_user(buf, in, sizeof(*in));
489 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
491 out.sem_otime = in->sem_otime;
492 out.sem_ctime = in->sem_ctime;
493 out.sem_nsems = in->sem_nsems;
495 return copy_to_user(buf, &out, sizeof(out));
502 static int semctl_nolock(int semid, int semnum, int cmd, int version, union semun arg)
505 struct sem_array *sma;
511 struct seminfo seminfo;
514 err = security_sem_semctl(NULL, cmd);
518 memset(&seminfo,0,sizeof(seminfo));
519 seminfo.semmni = sc_semmni;
520 seminfo.semmns = sc_semmns;
521 seminfo.semmsl = sc_semmsl;
522 seminfo.semopm = sc_semopm;
523 seminfo.semvmx = SEMVMX;
524 seminfo.semmnu = SEMMNU;
525 seminfo.semmap = SEMMAP;
526 seminfo.semume = SEMUME;
528 if (cmd == SEM_INFO) {
529 seminfo.semusz = sem_ids.in_use;
530 seminfo.semaem = used_sems;
532 seminfo.semusz = SEMUSZ;
533 seminfo.semaem = SEMAEM;
535 max_id = sem_ids.max_id;
537 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
539 return (max_id < 0) ? 0: max_id;
543 struct semid64_ds tbuf;
546 if(semid >= sem_ids.entries->size)
549 memset(&tbuf,0,sizeof(tbuf));
551 sma = sem_lock(semid);
556 if (ipcperms (&sma->sem_perm, S_IRUGO))
559 err = security_sem_semctl(sma, cmd);
563 id = sem_buildid(semid, sma->sem_perm.seq);
565 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
566 tbuf.sem_otime = sma->sem_otime;
567 tbuf.sem_ctime = sma->sem_ctime;
568 tbuf.sem_nsems = sma->sem_nsems;
570 if (copy_semid_to_user (arg.buf, &tbuf, version))
583 static int semctl_main(int semid, int semnum, int cmd, int version, union semun arg)
585 struct sem_array *sma;
588 ushort fast_sem_io[SEMMSL_FAST];
589 ushort* sem_io = fast_sem_io;
592 sma = sem_lock(semid);
596 nsems = sma->sem_nsems;
599 if (sem_checkid(sma,semid))
603 if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
606 err = security_sem_semctl(sma, cmd);
614 ushort __user *array = arg.array;
617 if(nsems > SEMMSL_FAST) {
621 sem_io = ipc_alloc(sizeof(ushort)*nsems);
623 ipc_lock_by_ptr(&sma->sem_perm);
629 ipc_lock_by_ptr(&sma->sem_perm);
631 if (sma->sem_perm.deleted) {
638 for (i = 0; i < sma->sem_nsems; i++)
639 sem_io[i] = sma->sem_base[i].semval;
642 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
654 if(nsems > SEMMSL_FAST) {
655 sem_io = ipc_alloc(sizeof(ushort)*nsems);
657 ipc_lock_by_ptr(&sma->sem_perm);
664 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
665 ipc_lock_by_ptr(&sma->sem_perm);
672 for (i = 0; i < nsems; i++) {
673 if (sem_io[i] > SEMVMX) {
674 ipc_lock_by_ptr(&sma->sem_perm);
681 ipc_lock_by_ptr(&sma->sem_perm);
683 if (sma->sem_perm.deleted) {
689 for (i = 0; i < nsems; i++)
690 sma->sem_base[i].semval = sem_io[i];
691 for (un = sma->undo; un; un = un->id_next)
692 for (i = 0; i < nsems; i++)
694 sma->sem_ctime = get_seconds();
695 /* maybe some queued-up processes were waiting for this */
702 struct semid64_ds tbuf;
703 memset(&tbuf,0,sizeof(tbuf));
704 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
705 tbuf.sem_otime = sma->sem_otime;
706 tbuf.sem_ctime = sma->sem_ctime;
707 tbuf.sem_nsems = sma->sem_nsems;
709 if (copy_semid_to_user (arg.buf, &tbuf, version))
713 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
716 if(semnum < 0 || semnum >= nsems)
719 curr = &sma->sem_base[semnum];
729 err = count_semncnt(sma,semnum);
732 err = count_semzcnt(sma,semnum);
739 if (val > SEMVMX || val < 0)
742 for (un = sma->undo; un; un = un->id_next)
743 un->semadj[semnum] = 0;
745 curr->sempid = current->tgid;
746 sma->sem_ctime = get_seconds();
747 /* maybe some queued-up processes were waiting for this */
756 if(sem_io != fast_sem_io)
757 ipc_free(sem_io, sizeof(ushort)*nsems);
767 static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __user *buf, int version)
772 struct semid64_ds tbuf;
774 if(copy_from_user(&tbuf, buf, sizeof(tbuf)))
777 out->uid = tbuf.sem_perm.uid;
778 out->gid = tbuf.sem_perm.gid;
779 out->mode = tbuf.sem_perm.mode;
785 struct semid_ds tbuf_old;
787 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
790 out->uid = tbuf_old.sem_perm.uid;
791 out->gid = tbuf_old.sem_perm.gid;
792 out->mode = tbuf_old.sem_perm.mode;
801 static int semctl_down(int semid, int semnum, int cmd, int version, union semun arg)
803 struct sem_array *sma;
805 struct sem_setbuf setbuf;
806 struct kern_ipc_perm *ipcp;
809 if(copy_semid_from_user (&setbuf, arg.buf, version))
811 if ((err = audit_ipc_perms(0, setbuf.uid, setbuf.gid, setbuf.mode)))
814 sma = sem_lock(semid);
818 if (sem_checkid(sma,semid)) {
822 ipcp = &sma->sem_perm;
824 if (current->euid != ipcp->cuid &&
825 current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
830 err = security_sem_semctl(sma, cmd);
840 ipcp->uid = setbuf.uid;
841 ipcp->gid = setbuf.gid;
842 ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
843 | (setbuf.mode & S_IRWXUGO);
844 sma->sem_ctime = get_seconds();
860 asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
868 version = ipc_parse_version(&cmd);
874 err = semctl_nolock(semid,semnum,cmd,version,arg);
884 err = semctl_main(semid,semnum,cmd,version,arg);
889 err = semctl_down(semid,semnum,cmd,version,arg);
897 static inline void lock_semundo(void)
899 struct sem_undo_list *undo_list;
901 undo_list = current->sysvsem.undo_list;
903 spin_lock(&undo_list->lock);
906 /* This code has an interaction with copy_semundo().
907 * Consider; two tasks are sharing the undo_list. task1
908 * acquires the undo_list lock in lock_semundo(). If task2 now
909 * exits before task1 releases the lock (by calling
910 * unlock_semundo()), then task1 will never call spin_unlock().
911 * This leave the sem_undo_list in a locked state. If task1 now creats task3
912 * and once again shares the sem_undo_list, the sem_undo_list will still be
913 * locked, and future SEM_UNDO operations will deadlock. This case is
914 * dealt with in copy_semundo() by having it reinitialize the spin lock when
915 * the refcnt goes from 1 to 2.
917 static inline void unlock_semundo(void)
919 struct sem_undo_list *undo_list;
921 undo_list = current->sysvsem.undo_list;
923 spin_unlock(&undo_list->lock);
927 /* If the task doesn't already have a undo_list, then allocate one
928 * here. We guarantee there is only one thread using this undo list,
929 * and current is THE ONE
931 * If this allocation and assignment succeeds, but later
932 * portions of this code fail, there is no need to free the sem_undo_list.
933 * Just let it stay associated with the task, and it'll be freed later
936 * This can block, so callers must hold no locks.
938 static inline int get_undo_list(struct sem_undo_list **undo_listp)
940 struct sem_undo_list *undo_list;
943 undo_list = current->sysvsem.undo_list;
945 size = sizeof(struct sem_undo_list);
946 undo_list = (struct sem_undo_list *) kmalloc(size, GFP_KERNEL);
947 if (undo_list == NULL)
949 memset(undo_list, 0, size);
950 spin_lock_init(&undo_list->lock);
951 atomic_set(&undo_list->refcnt, 1);
952 current->sysvsem.undo_list = undo_list;
954 *undo_listp = undo_list;
958 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
960 struct sem_undo **last, *un;
962 last = &ulp->proc_list;
978 static struct sem_undo *find_undo(int semid)
980 struct sem_array *sma;
981 struct sem_undo_list *ulp;
982 struct sem_undo *un, *new;
986 error = get_undo_list(&ulp);
988 return ERR_PTR(error);
991 un = lookup_undo(ulp, semid);
993 if (likely(un!=NULL))
996 /* no undo structure around - allocate one. */
997 sma = sem_lock(semid);
998 un = ERR_PTR(-EINVAL);
1001 un = ERR_PTR(-EIDRM);
1002 if (sem_checkid(sma,semid)) {
1006 nsems = sma->sem_nsems;
1007 ipc_rcu_getref(sma);
1010 new = (struct sem_undo *) kmalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1012 ipc_lock_by_ptr(&sma->sem_perm);
1013 ipc_rcu_putref(sma);
1015 return ERR_PTR(-ENOMEM);
1017 memset(new, 0, sizeof(struct sem_undo) + sizeof(short)*nsems);
1018 new->semadj = (short *) &new[1];
1022 un = lookup_undo(ulp, semid);
1026 ipc_lock_by_ptr(&sma->sem_perm);
1027 ipc_rcu_putref(sma);
1031 ipc_lock_by_ptr(&sma->sem_perm);
1032 ipc_rcu_putref(sma);
1033 if (sma->sem_perm.deleted) {
1037 un = ERR_PTR(-EIDRM);
1040 new->proc_next = ulp->proc_list;
1041 ulp->proc_list = new;
1042 new->id_next = sma->undo;
1051 asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
1052 unsigned nsops, const struct timespec __user *timeout)
1054 int error = -EINVAL;
1055 struct sem_array *sma;
1056 struct sembuf fast_sops[SEMOPM_FAST];
1057 struct sembuf* sops = fast_sops, *sop;
1058 struct sem_undo *un;
1059 int undos = 0, alter = 0, max;
1060 struct sem_queue queue;
1061 unsigned long jiffies_left = 0;
1063 if (nsops < 1 || semid < 0)
1065 if (nsops > sc_semopm)
1067 if(nsops > SEMOPM_FAST) {
1068 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1072 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1077 struct timespec _timeout;
1078 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1082 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1083 _timeout.tv_nsec >= 1000000000L) {
1087 jiffies_left = timespec_to_jiffies(&_timeout);
1090 for (sop = sops; sop < sops + nsops; sop++) {
1091 if (sop->sem_num >= max)
1093 if (sop->sem_flg & SEM_UNDO)
1095 if (sop->sem_op != 0)
1101 un = find_undo(semid);
1103 error = PTR_ERR(un);
1109 sma = sem_lock(semid);
1114 if (sem_checkid(sma,semid))
1115 goto out_unlock_free;
1117 * semid identifies are not unique - find_undo may have
1118 * allocated an undo structure, it was invalidated by an RMID
1119 * and now a new array with received the same id. Check and retry.
1121 if (un && un->semid == -1) {
1126 if (max >= sma->sem_nsems)
1127 goto out_unlock_free;
1130 if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1131 goto out_unlock_free;
1133 error = security_sem_semop(sma, sops, nsops, alter);
1135 goto out_unlock_free;
1137 error = try_atomic_semop (sma, sops, nsops, un, current->tgid);
1139 if (alter && error == 0)
1141 goto out_unlock_free;
1144 /* We need to sleep on this operation, so we put the current
1145 * task into the pending queue and go to sleep.
1150 queue.nsops = nsops;
1152 queue.pid = current->tgid;
1154 queue.alter = alter;
1156 append_to_queue(sma ,&queue);
1158 prepend_to_queue(sma ,&queue);
1160 queue.status = -EINTR;
1161 queue.sleeper = current;
1162 current->state = TASK_INTERRUPTIBLE;
1166 jiffies_left = schedule_timeout(jiffies_left);
1170 error = queue.status;
1171 while(unlikely(error == IN_WAKEUP)) {
1173 error = queue.status;
1176 if (error != -EINTR) {
1177 /* fast path: update_queue already obtained all requested
1182 sma = sem_lock(semid);
1184 if(queue.prev != NULL)
1191 * If queue.status != -EINTR we are woken up by another process
1193 error = queue.status;
1194 if (error != -EINTR) {
1195 goto out_unlock_free;
1199 * If an interrupt occurred we have to clean up the queue
1201 if (timeout && jiffies_left == 0)
1203 remove_from_queue(sma,&queue);
1204 goto out_unlock_free;
1209 if(sops != fast_sops)
1214 asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
1216 return sys_semtimedop(semid, tsops, nsops, NULL);
1219 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1220 * parent and child tasks.
1222 * See the notes above unlock_semundo() regarding the spin_lock_init()
1223 * in this code. Initialize the undo_list->lock here instead of get_undo_list()
1224 * because of the reasoning in the comment above unlock_semundo.
1227 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1229 struct sem_undo_list *undo_list;
1232 if (clone_flags & CLONE_SYSVSEM) {
1233 error = get_undo_list(&undo_list);
1236 atomic_inc(&undo_list->refcnt);
1237 tsk->sysvsem.undo_list = undo_list;
1239 tsk->sysvsem.undo_list = NULL;
1245 * add semadj values to semaphores, free undo structures.
1246 * undo structures are not freed when semaphore arrays are destroyed
1247 * so some of them may be out of date.
1248 * IMPLEMENTATION NOTE: There is some confusion over whether the
1249 * set of adjustments that needs to be done should be done in an atomic
1250 * manner or not. That is, if we are attempting to decrement the semval
1251 * should we queue up and wait until we can do so legally?
1252 * The original implementation attempted to do this (queue and wait).
1253 * The current implementation does not do so. The POSIX standard
1254 * and SVID should be consulted to determine what behavior is mandated.
1256 void exit_sem(struct task_struct *tsk)
1258 struct sem_undo_list *undo_list;
1259 struct sem_undo *u, **up;
1261 undo_list = tsk->sysvsem.undo_list;
1265 if (!atomic_dec_and_test(&undo_list->refcnt))
1268 /* There's no need to hold the semundo list lock, as current
1269 * is the last task exiting for this undo list.
1271 for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
1272 struct sem_array *sma;
1274 struct sem_undo *un, **unp;
1281 sma = sem_lock(semid);
1288 BUG_ON(sem_checkid(sma,u->semid));
1290 /* remove u from the sma->undo list */
1291 for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
1295 printk ("exit_sem undo list error id=%d\n", u->semid);
1299 /* perform adjustments registered in u */
1300 nsems = sma->sem_nsems;
1301 for (i = 0; i < nsems; i++) {
1302 struct sem * sem = &sma->sem_base[i];
1304 sem->semval += u->semadj[i];
1306 * Range checks of the new semaphore value,
1307 * not defined by sus:
1308 * - Some unices ignore the undo entirely
1309 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1310 * - some cap the value (e.g. FreeBSD caps
1311 * at 0, but doesn't enforce SEMVMX)
1313 * Linux caps the semaphore value, both at 0
1316 * Manfred <manfred@colorfullife.com>
1318 if (sem->semval < 0)
1320 if (sem->semval > SEMVMX)
1321 sem->semval = SEMVMX;
1322 sem->sempid = current->tgid;
1325 sma->sem_otime = get_seconds();
1326 /* maybe some queued-up processes were waiting for this */
1334 #ifdef CONFIG_PROC_FS
1335 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
1337 struct sem_array *sma = it;
1339 return seq_printf(s,
1340 "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",