/* * linux/ipc/sem.c * Copyright (C) 1992 Krishna Balasubramanian * Copyright (C) 1995 Eric Schenk, Bruno Haible * * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995): * This code underwent a massive rewrite in order to solve some problems * with the original code. In particular the original code failed to * wake up processes that were waiting for semval to go to 0 if the * value went to 0 and was then incremented rapidly enough. In solving * this problem I have also modified the implementation so that it * processes pending operations in a FIFO manner, thus give a guarantee * that processes waiting for a lock on the semaphore won't starve * unless another locking process fails to unlock. * In addition the following two changes in behavior have been introduced: * - The original implementation of semop returned the value * last semaphore element examined on success. This does not * match the manual page specifications, and effectively * allows the user to read the semaphore even if they do not * have read permissions. The implementation now returns 0 * on success as stated in the manual page. * - There is some confusion over whether the set of undo adjustments * to be performed at exit should be done in an atomic manner. * That is, if we are attempting to decrement the semval should we queue * up and wait until we can do so legally? * The original implementation attempted to do this. * The current implementation does not do so. This is because I don't * think it is the right thing (TM) to do, and because I couldn't * see a clean way to get the old behavior with the new design. * The POSIX standard and SVID should be consulted to determine * what behavior is mandated. * * Further notes on refinement (Christoph Rohland, December 1998): * - The POSIX standard says, that the undo adjustments simply should * redo. So the current implementation is o.K. * - The previous code had two flaws: * 1) It actively gave the semaphore to the next waiting process * sleeping on the semaphore. Since this process did not have the * cpu this led to many unnecessary context switches and bad * performance. Now we only check which process should be able to * get the semaphore and if this process wants to reduce some * semaphore value we simply wake it up without doing the * operation. So it has to try to get it later. Thus e.g. the * running process may reacquire the semaphore during the current * time slice. If it only waits for zero or increases the semaphore, * we do the operation in advance and wake it up. * 2) It did not wake up all zero waiting processes. We try to do * better but only get the semops right which only wait for zero or * increase. If there are decrement operations in the operations * array we do the same as before. * * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> * * SMP-threaded, sysctl's added * (c) 1999 Manfred Spraul <manfreds@colorfullife.com> */ #include <linux/config.h> #include <linux/malloc.h> #include <linux/spinlock.h> #include <linux/init.h> #include <linux/proc_fs.h> #include <asm/uaccess.h> #include "util.h" #define sem_lock(id) ((struct sem_array*)ipc_lock(&sem_ids,id)) #define sem_unlock(id) ipc_unlock(&sem_ids,id) #define sem_rmid(id) ((struct sem_array*)ipc_rmid(&sem_ids,id)) #define sem_checkid(sma, semid) \ ipc_checkid(&sem_ids,&sma->sem_perm,semid) #define sem_buildid(id, seq) \ ipc_buildid(&sem_ids, id, seq) static struct ipc_ids sem_ids; static int newary (key_t, int, int); static void freeary (int id); #ifdef CONFIG_PROC_FS static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data); #endif #define SEMMSL_FAST 256 /* 512 bytes on stack */ #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ /* * linked list protection: * sem_undo.id_next, * sem_array.sem_pending{,last}, * sem_array.sem_undo: sem_lock() for read/write * sem_undo.proc_next: only "current" is allowed to read/write that field. * */ int sem_ctls[4] = {SEMMSL, SEMMNS, SEMOPM, SEMMNI}; #define sc_semmsl (sem_ctls[0]) #define sc_semmns (sem_ctls[1]) #define sc_semopm (sem_ctls[2]) #define sc_semmni (sem_ctls[3]) static int used_sems; 102 void __init sem_init (void) { used_sems = 0; ipc_init_ids(&sem_ids,sc_semmni); #ifdef CONFIG_PROC_FS create_proc_read_entry("sysvipc/sem", 0, 0, sysvipc_sem_read_proc, NULL); #endif } 112 static int newary (key_t key, int nsems, int semflg) { int id; struct sem_array *sma; int size; 118 if (!nsems) 119 return -EINVAL; 120 if (used_sems + nsems > sc_semmns) 121 return -ENOSPC; size = sizeof (*sma) + nsems * sizeof (struct sem); sma = (struct sem_array *) ipc_alloc(size); 125 if (!sma) { 126 return -ENOMEM; } memset (sma, 0, size); id = ipc_addid(&sem_ids, &sma->sem_perm, sc_semmni); 130 if(id == -1) { ipc_free(sma, size); 132 return -ENOSPC; } used_sems += nsems; sma->sem_perm.mode = (semflg & S_IRWXUGO); sma->sem_perm.key = key; sma->sem_base = (struct sem *) &sma[1]; /* sma->sem_pending = NULL; */ sma->sem_pending_last = &sma->sem_pending; /* sma->undo = NULL; */ sma->sem_nsems = nsems; sma->sem_ctime = CURRENT_TIME; sem_unlock(id); 147 return sem_buildid(id, sma->sem_perm.seq); } 150 asmlinkage long sys_semget (key_t key, int nsems, int semflg) { int id, err = -EINVAL; struct sem_array *sma; 155 if (nsems < 0 || nsems > sc_semmsl) 156 return -EINVAL; down(&sem_ids.sem); 159 if (key == IPC_PRIVATE) { err = newary(key, nsems, semflg); 161 } else if ((id = ipc_findkey(&sem_ids, key)) == -1) { /* key not used */ 162 if (!(semflg & IPC_CREAT)) err = -ENOENT; 164 else err = newary(key, nsems, semflg); 166 } else if (semflg & IPC_CREAT && semflg & IPC_EXCL) { err = -EEXIST; 168 } else { sma = sem_lock(id); 170 if(sma==NULL) 171 BUG(); 172 if (nsems > sma->sem_nsems) err = -EINVAL; 174 else if (ipcperms(&sma->sem_perm, semflg)) err = -EACCES; 176 else err = sem_buildid(id, sma->sem_perm.seq); sem_unlock(id); } up(&sem_ids.sem); 182 return err; } /* doesn't acquire the sem_lock on error! */ 186 static int sem_revalidate(int semid, struct sem_array* sma, int nsems, short flg) { struct sem_array* smanew; smanew = sem_lock(semid); 191 if(smanew==NULL) 192 return -EIDRM; 193 if(smanew != sma || sem_checkid(sma,semid) || sma->sem_nsems != nsems) { sem_unlock(semid); 195 return -EIDRM; } 198 if (ipcperms(&sma->sem_perm, flg)) { sem_unlock(semid); 200 return -EACCES; } 202 return 0; } /* Manage the doubly linked list sma->sem_pending as a FIFO: * insert new queue elements at the tail sma->sem_pending_last. */ 207 static inline void append_to_queue (struct sem_array * sma, struct sem_queue * q) { *(q->prev = sma->sem_pending_last) = q; *(sma->sem_pending_last = &q->next) = NULL; } 214 static inline void prepend_to_queue (struct sem_array * sma, struct sem_queue * q) { q->next = sma->sem_pending; *(q->prev = &sma->sem_pending) = q; 219 if (q->next) q->next->prev = &q->next; 221 else /* sma->sem_pending_last == &sma->sem_pending */ sma->sem_pending_last = &q->next; } 225 static inline void remove_from_queue (struct sem_array * sma, struct sem_queue * q) { *(q->prev) = q->next; 229 if (q->next) q->next->prev = q->prev; 231 else /* sma->sem_pending_last == &q->next */ sma->sem_pending_last = q->prev; q->prev = NULL; /* mark as removed */ } /* * Determine whether a sequence of semaphore operations would succeed * all at once. Return 0 if yes, 1 if need to sleep, else return error code. */ 241 static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops, int nsops, struct sem_undo *un, int pid, int do_undo) { int result, sem_op; struct sembuf *sop; struct sem * curr; 249 for (sop = sops; sop < sops + nsops; sop++) { curr = sma->sem_base + sop->sem_num; sem_op = sop->sem_op; 253 if (!sem_op && curr->semval) 254 goto would_block; curr->sempid = (curr->sempid << 16) | pid; curr->semval += sem_op; 258 if (sop->sem_flg & SEM_UNDO) un->semadj[sop->sem_num] -= sem_op; 261 if (curr->semval < 0) 262 goto would_block; 263 if (curr->semval > SEMVMX) 264 goto out_of_range; } 267 if (do_undo) { sop--; result = 0; 271 goto undo; } sma->sem_otime = CURRENT_TIME; 275 return 0; out_of_range: result = -ERANGE; 279 goto undo; would_block: 282 if (sop->sem_flg & IPC_NOWAIT) result = -EAGAIN; 284 else result = 1; undo: 288 while (sop >= sops) { curr = sma->sem_base + sop->sem_num; curr->semval -= sop->sem_op; curr->sempid >>= 16; 293 if (sop->sem_flg & SEM_UNDO) un->semadj[sop->sem_num] += sop->sem_op; sop--; } 298 return result; } /* Go through the pending queue for the indicated semaphore * looking for tasks that can be completed. */ 304 static void update_queue (struct sem_array * sma) { int error; struct sem_queue * q; 309 for (q = sma->sem_pending; q; q = q->next) { 311 if (q->status == 1) 312 continue; /* this one was woken up before */ error = try_atomic_semop(sma, q->sops, q->nsops, q->undo, q->pid, q->alter); /* Does q->sleeper still need to sleep? */ 318 if (error <= 0) { /* Found one, wake it up */ wake_up_process(q->sleeper); 321 if (error == 0 && q->alter) { /* if q-> alter let it self try */ q->status = 1; 324 return; } q->status = error; remove_from_queue(sma,q); } } } /* The following counts are associated to each semaphore: * semncnt number of tasks waiting on semval being nonzero * semzcnt number of tasks waiting on semval being zero * This model assumes that a task waits on exactly one semaphore. * Since semaphore operations are to be performed atomically, tasks actually * wait on a whole sequence of semaphores simultaneously. * The counts we return here are a rough approximation, but still * warrant that semncnt+semzcnt>0 if the task is on the pending queue. */ 341 static int count_semncnt (struct sem_array * sma, ushort semnum) { int semncnt; struct sem_queue * q; semncnt = 0; 347 for (q = sma->sem_pending; q; q = q->next) { struct sembuf * sops = q->sops; int nsops = q->nsops; int i; 351 for (i = 0; i < nsops; i++) if (sops[i].sem_num == semnum && (sops[i].sem_op < 0) 354 && !(sops[i].sem_flg & IPC_NOWAIT)) semncnt++; } 357 return semncnt; } 359 static int count_semzcnt (struct sem_array * sma, ushort semnum) { int semzcnt; struct sem_queue * q; semzcnt = 0; 365 for (q = sma->sem_pending; q; q = q->next) { struct sembuf * sops = q->sops; int nsops = q->nsops; int i; 369 for (i = 0; i < nsops; i++) if (sops[i].sem_num == semnum && (sops[i].sem_op == 0) 372 && !(sops[i].sem_flg & IPC_NOWAIT)) semzcnt++; } 375 return semzcnt; } /* Free a semaphore set. */ 379 static void freeary (int id) { struct sem_array *sma; struct sem_undo *un; struct sem_queue *q; int size; sma = sem_rmid(id); /* Invalidate the existing undo structures for this semaphore set. * (They will be freed without any further action in sem_exit() * or during the next semop.) */ 392 for (un = sma->undo; un; un = un->id_next) un->semid = -1; /* Wake up all pending processes and let them fail with EIDRM. */ 396 for (q = sma->sem_pending; q; q = q->next) { q->status = -EIDRM; q->prev = NULL; wake_up_process(q->sleeper); /* doesn't sleep */ } sem_unlock(id); used_sems -= sma->sem_nsems; size = sizeof (*sma) + sma->sem_nsems * sizeof (struct sem); ipc_free(sma, size); } 408 static unsigned long copy_semid_to_user(void *buf, struct semid64_ds *in, int version) { 410 switch(version) { 411 case IPC_64: 412 return copy_to_user(buf, in, sizeof(*in)); 413 case IPC_OLD: { struct semid_ds out; ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); out.sem_otime = in->sem_otime; out.sem_ctime = in->sem_ctime; out.sem_nsems = in->sem_nsems; 423 return copy_to_user(buf, &out, sizeof(out)); } 425 default: 426 return -EINVAL; } } 430 int semctl_nolock(int semid, int semnum, int cmd, int version, union semun arg) { int err = -EINVAL; 434 switch(cmd) { 435 case IPC_INFO: 436 case SEM_INFO: { struct seminfo seminfo; int max_id; memset(&seminfo,0,sizeof(seminfo)); seminfo.semmni = sc_semmni; seminfo.semmns = sc_semmns; seminfo.semmsl = sc_semmsl; seminfo.semopm = sc_semopm; seminfo.semvmx = SEMVMX; seminfo.semmnu = SEMMNU; seminfo.semmap = SEMMAP; seminfo.semume = SEMUME; down(&sem_ids.sem); 451 if (cmd == SEM_INFO) { seminfo.semusz = sem_ids.in_use; seminfo.semaem = used_sems; 454 } else { seminfo.semusz = SEMUSZ; seminfo.semaem = SEMAEM; } max_id = sem_ids.max_id; up(&sem_ids.sem); 460 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo))) 461 return -EFAULT; 462 return (max_id < 0) ? 0: max_id; } 464 case SEM_STAT: { struct sem_array *sma; struct semid64_ds tbuf; int id; 470 if(semid > sem_ids.size) 471 return -EINVAL; memset(&tbuf,0,sizeof(tbuf)); sma = sem_lock(semid); 476 if(sma == NULL) 477 return -EINVAL; err = -EACCES; 480 if (ipcperms (&sma->sem_perm, S_IRUGO)) 481 goto out_unlock; id = sem_buildid(semid, sma->sem_perm.seq); kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); tbuf.sem_otime = sma->sem_otime; tbuf.sem_ctime = sma->sem_ctime; tbuf.sem_nsems = sma->sem_nsems; sem_unlock(semid); 489 if (copy_semid_to_user (arg.buf, &tbuf, version)) 490 return -EFAULT; 491 return id; } 493 default: 494 return -EINVAL; } 496 return err; out_unlock: sem_unlock(semid); 499 return err; } 502 int semctl_main(int semid, int semnum, int cmd, int version, union semun arg) { struct sem_array *sma; struct sem* curr; int err; ushort fast_sem_io[SEMMSL_FAST]; ushort* sem_io = fast_sem_io; int nsems; sma = sem_lock(semid); 512 if(sma==NULL) 513 return -EINVAL; nsems = sma->sem_nsems; err=-EIDRM; 518 if (sem_checkid(sma,semid)) 519 goto out_unlock; err = -EACCES; 522 if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO)) 523 goto out_unlock; 525 switch (cmd) { 526 case GETALL: { ushort *array = arg.array; int i; 531 if(nsems > SEMMSL_FAST) { sem_unlock(semid); sem_io = ipc_alloc(sizeof(ushort)*nsems); 534 if(sem_io == NULL) 535 return -ENOMEM; err = sem_revalidate(semid, sma, nsems, S_IRUGO); 537 if(err) 538 goto out_free; } 541 for (i = 0; i < sma->sem_nsems; i++) sem_io[i] = sma->sem_base[i].semval; sem_unlock(semid); err = 0; 545 if(copy_to_user(array, sem_io, nsems*sizeof(ushort))) err = -EFAULT; 547 goto out_free; } 549 case SETALL: { int i; struct sem_undo *un; sem_unlock(semid); 556 if(nsems > SEMMSL_FAST) { sem_io = ipc_alloc(sizeof(ushort)*nsems); 558 if(sem_io == NULL) 559 return -ENOMEM; } 562 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) { err = -EFAULT; 564 goto out_free; } 567 for (i = 0; i < nsems; i++) { 568 if (sem_io[i] > SEMVMX) { err = -ERANGE; 570 goto out_free; } } err = sem_revalidate(semid, sma, nsems, S_IWUGO); 574 if(err) 575 goto out_free; 577 for (i = 0; i < nsems; i++) sma->sem_base[i].semval = sem_io[i]; 579 for (un = sma->undo; un; un = un->id_next) 580 for (i = 0; i < nsems; i++) un->semadj[i] = 0; sma->sem_ctime = CURRENT_TIME; /* maybe some queued-up processes were waiting for this */ update_queue(sma); err = 0; 586 goto out_unlock; } 588 case IPC_STAT: { struct semid64_ds tbuf; memset(&tbuf,0,sizeof(tbuf)); kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); tbuf.sem_otime = sma->sem_otime; tbuf.sem_ctime = sma->sem_ctime; tbuf.sem_nsems = sma->sem_nsems; sem_unlock(semid); 597 if (copy_semid_to_user (arg.buf, &tbuf, version)) 598 return -EFAULT; 599 return 0; } /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */ } err = -EINVAL; 604 if(semnum < 0 || semnum >= nsems) 605 goto out_unlock; curr = &sma->sem_base[semnum]; 609 switch (cmd) { 610 case GETVAL: err = curr->semval; 612 goto out_unlock; 613 case GETPID: err = curr->sempid & 0xffff; 615 goto out_unlock; 616 case GETNCNT: err = count_semncnt(sma,semnum); 618 goto out_unlock; 619 case GETZCNT: err = count_semzcnt(sma,semnum); 621 goto out_unlock; 622 case SETVAL: { int val = arg.val; struct sem_undo *un; err = -ERANGE; 627 if (val > SEMVMX || val < 0) 628 goto out_unlock; 630 for (un = sma->undo; un; un = un->id_next) un->semadj[semnum] = 0; curr->semval = val; sma->sem_ctime = CURRENT_TIME; /* maybe some queued-up processes were waiting for this */ update_queue(sma); err = 0; 637 goto out_unlock; } } out_unlock: sem_unlock(semid); out_free: 643 if(sem_io != fast_sem_io) ipc_free(sem_io, sizeof(ushort)*nsems); 645 return err; } struct sem_setbuf { uid_t uid; gid_t gid; mode_t mode; }; 654 static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void *buf, int version) { 656 switch(version) { 657 case IPC_64: { struct semid64_ds tbuf; 661 if(copy_from_user(&tbuf, buf, sizeof(tbuf))) 662 return -EFAULT; out->uid = tbuf.sem_perm.uid; out->gid = tbuf.sem_perm.gid; out->mode = tbuf.sem_perm.mode; 668 return 0; } 670 case IPC_OLD: { struct semid_ds tbuf_old; 674 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) 675 return -EFAULT; out->uid = tbuf_old.sem_perm.uid; out->gid = tbuf_old.sem_perm.gid; out->mode = tbuf_old.sem_perm.mode; 681 return 0; } 683 default: 684 return -EINVAL; } } 688 int semctl_down(int semid, int semnum, int cmd, int version, union semun arg) { struct sem_array *sma; int err; struct sem_setbuf setbuf; struct kern_ipc_perm *ipcp; 695 if(cmd == IPC_SET) { 696 if(copy_semid_from_user (&setbuf, arg.buf, version)) 697 return -EFAULT; } sma = sem_lock(semid); 700 if(sma==NULL) 701 return -EINVAL; 703 if (sem_checkid(sma,semid)) { err=-EIDRM; 705 goto out_unlock; } ipcp = &sma->sem_perm; if (current->euid != ipcp->cuid && 710 current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) { err=-EPERM; 712 goto out_unlock; } 715 switch(cmd){ 716 case IPC_RMID: freeary(semid); err = 0; 719 break; 720 case IPC_SET: ipcp->uid = setbuf.uid; ipcp->gid = setbuf.gid; ipcp->mode = (ipcp->mode & ~S_IRWXUGO) | (setbuf.mode & S_IRWXUGO); sma->sem_ctime = CURRENT_TIME; sem_unlock(semid); err = 0; 728 break; 729 default: sem_unlock(semid); err = -EINVAL; 732 break; } 734 return err; out_unlock: sem_unlock(semid); 738 return err; } 741 asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg) { int err = -EINVAL; int version; 746 if (semid < 0) 747 return -EINVAL; version = ipc_parse_version(&cmd); 751 switch(cmd) { 752 case IPC_INFO: 753 case SEM_INFO: 754 case SEM_STAT: err = semctl_nolock(semid,semnum,cmd,version,arg); 756 return err; 757 case GETALL: 758 case GETVAL: 759 case GETPID: 760 case GETNCNT: 761 case GETZCNT: 762 case IPC_STAT: 763 case SETVAL: 764 case SETALL: err = semctl_main(semid,semnum,cmd,version,arg); 766 return err; 767 case IPC_RMID: 768 case IPC_SET: down(&sem_ids.sem); err = semctl_down(semid,semnum,cmd,version,arg); up(&sem_ids.sem); 772 return err; 773 default: 774 return -EINVAL; } } 778 static struct sem_undo* freeundos(struct sem_array *sma, struct sem_undo* un) { struct sem_undo* u; struct sem_undo** up; 783 for(up = ¤t->semundo;(u=*up);up=&u->proc_next) { 784 if(un==u) { un=u->proc_next; *up=un; kfree(u); 788 return un; } } printk ("freeundos undo list error id=%d\n", un->semid); 792 return un->proc_next; } /* returns without sem_lock on error! */ 796 static int alloc_undo(struct sem_array *sma, struct sem_undo** unp, int semid, int alter) { int size, nsems, error; struct sem_undo *un; nsems = sma->sem_nsems; size = sizeof(struct sem_undo) + sizeof(short)*nsems; sem_unlock(semid); un = (struct sem_undo *) kmalloc(size, GFP_KERNEL); 806 if (!un) 807 return -ENOMEM; memset(un, 0, size); error = sem_revalidate(semid, sma, nsems, alter ? S_IWUGO : S_IRUGO); 811 if(error) { kfree(un); 813 return error; } un->semadj = (short *) &un[1]; un->semid = semid; un->proc_next = current->semundo; current->semundo = un; un->id_next = sma->undo; sma->undo = un; *unp = un; 823 return 0; } 826 asmlinkage long sys_semop (int semid, struct sembuf *tsops, unsigned nsops) { int error = -EINVAL; struct sem_array *sma; struct sembuf fast_sops[SEMOPM_FAST]; struct sembuf* sops = fast_sops, *sop; struct sem_undo *un; int undos = 0, decrease = 0, alter = 0; struct sem_queue queue; 836 if (nsops < 1 || semid < 0) 837 return -EINVAL; 838 if (nsops > sc_semopm) 839 return -E2BIG; 840 if(nsops > SEMOPM_FAST) { sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL); 842 if(sops==NULL) 843 return -ENOMEM; } 845 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) { error=-EFAULT; 847 goto out_free; } sma = sem_lock(semid); error=-EINVAL; 851 if(sma==NULL) 852 goto out_free; error = -EIDRM; 854 if (sem_checkid(sma,semid)) 855 goto out_unlock_free; error = -EFBIG; 857 for (sop = sops; sop < sops + nsops; sop++) { 858 if (sop->sem_num >= sma->sem_nsems) 859 goto out_unlock_free; 860 if (sop->sem_flg & SEM_UNDO) undos++; 862 if (sop->sem_op < 0) decrease = 1; 864 if (sop->sem_op > 0) alter = 1; } alter |= decrease; error = -EACCES; 870 if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) 871 goto out_unlock_free; 872 if (undos) { /* Make sure we have an undo structure * for this process and this semaphore set. */ un=current->semundo; 877 while(un != NULL) { 878 if(un->semid==semid) 879 break; 880 if(un->semid==-1) un=freeundos(sma,un); 882 else un=un->proc_next; } 885 if (!un) { error = alloc_undo(sma,&un,semid,alter); 887 if(error) 888 goto out_free; } 890 } else un = NULL; error = try_atomic_semop (sma, sops, nsops, un, current->pid, 0); 894 if (error <= 0) 895 goto update; /* We need to sleep on this operation, so we put the current * task into the pending queue and go to sleep. */ queue.sma = sma; queue.sops = sops; queue.nsops = nsops; queue.undo = un; queue.pid = current->pid; queue.alter = decrease; queue.id = semid; 908 if (alter) append_to_queue(sma ,&queue); 910 else prepend_to_queue(sma ,&queue); current->semsleeping = &queue; 914 for (;;) { struct sem_array* tmp; queue.status = -EINTR; queue.sleeper = current; current->state = TASK_INTERRUPTIBLE; sem_unlock(semid); schedule(); tmp = sem_lock(semid); 924 if(tmp==NULL) { 925 if(queue.status != -EIDRM) 926 BUG(); current->semsleeping = NULL; error = -EIDRM; 929 goto out_free; } /* * If queue.status == 1 we where woken up and * have to retry else we simply return. * If an interrupt occurred we have to clean up the * queue * */ 938 if (queue.status == 1) { error = try_atomic_semop (sma, sops, nsops, un, current->pid,0); 942 if (error <= 0) 943 break; 944 } else { error = queue.status; 946 if (queue.prev) /* got Interrupt */ 947 break; /* Everything done by update_queue */ current->semsleeping = NULL; 950 goto out_unlock_free; } } current->semsleeping = NULL; remove_from_queue(sma,&queue); update: 956 if (alter) update_queue (sma); out_unlock_free: sem_unlock(semid); out_free: 961 if(sops != fast_sops) kfree(sops); 963 return error; } /* * add semadj values to semaphores, free undo structures. * undo structures are not freed when semaphore arrays are destroyed * so some of them may be out of date. * IMPLEMENTATION NOTE: There is some confusion over whether the * set of adjustments that needs to be done should be done in an atomic * manner or not. That is, if we are attempting to decrement the semval * should we queue up and wait until we can do so legally? * The original implementation attempted to do this (queue and wait). * The current implementation does not do so. The POSIX standard * and SVID should be consulted to determine what behavior is mandated. */ 978 void sem_exit (void) { struct sem_queue *q; struct sem_undo *u, *un = NULL, **up, **unp; struct sem_array *sma; int nsems, i; /* If the current process was sleeping for a semaphore, * remove it from the queue. */ 988 if ((q = current->semsleeping)) { int semid = q->id; sma = sem_lock(semid); current->semsleeping = NULL; 993 if (q->prev) { 994 if(sma==NULL) 995 BUG(); remove_from_queue(q->sma,q); } 998 if(sma!=NULL) sem_unlock(semid); } 1002 for (up = ¤t->semundo; (u = *up); *up = u->proc_next, kfree(u)) { int semid = u->semid; 1004 if(semid == -1) 1005 continue; sma = sem_lock(semid); 1007 if (sma == NULL) 1008 continue; 1010 if (u->semid == -1) 1011 goto next_entry; 1013 if (sem_checkid(sma,u->semid)) 1014 goto next_entry; /* remove u from the sma->undo list */ 1017 for (unp = &sma->undo; (un = *unp); unp = &un->id_next) { 1018 if (u == un) 1019 goto found; } printk ("sem_exit undo list error id=%d\n", u->semid); 1022 goto next_entry; found: *unp = un->id_next; /* perform adjustments registered in u */ nsems = sma->sem_nsems; 1027 for (i = 0; i < nsems; i++) { struct sem * sem = &sma->sem_base[i]; sem->semval += u->semadj[i]; 1030 if (sem->semval < 0) sem->semval = 0; /* shouldn't happen */ sem->sempid = current->pid; } sma->sem_otime = CURRENT_TIME; /* maybe some queued-up processes were waiting for this */ update_queue(sma); next_entry: sem_unlock(semid); } current->semundo = NULL; } #ifdef CONFIG_PROC_FS 1044 static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data) { off_t pos = 0; off_t begin = 0; int i, len = 0; len += sprintf(buffer, " key semid perms nsems uid gid cuid cgid otime ctime\n"); down(&sem_ids.sem); 1053 for(i = 0; i <= sem_ids.max_id; i++) { struct sem_array *sma; sma = sem_lock(i); 1056 if(sma) { len += sprintf(buffer + len, "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n", sma->sem_perm.key, sem_buildid(i,sma->sem_perm.seq), sma->sem_perm.mode, sma->sem_nsems, sma->sem_perm.uid, sma->sem_perm.gid, sma->sem_perm.cuid, sma->sem_perm.cgid, sma->sem_otime, sma->sem_ctime); sem_unlock(i); pos += len; 1071 if(pos < offset) { len = 0; begin = pos; } 1075 if(pos > offset + length) 1076 goto done; } } *eof = 1; done: up(&sem_ids.sem); *start = buffer + (offset - begin); len -= (offset - begin); 1084 if(len > length) len = length; 1086 if(len < 0) len = 0; 1088 return len; } #endif