linux/ipc/sem.c
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   1/*
   2 * linux/ipc/sem.c
   3 * Copyright (C) 1992 Krishna Balasubramanian
   4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
   5 *
   6 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
   7 *
   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
  12 * Lockless wakeup
  13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
  14 * Further wakeup optimizations, documentation
  15 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
  16 *
  17 * support for audit of ipc object properties and permission changes
  18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
  19 *
  20 * namespaces support
  21 * OpenVZ, SWsoft Inc.
  22 * Pavel Emelianov <xemul@openvz.org>
  23 *
  24 * Implementation notes: (May 2010)
  25 * This file implements System V semaphores.
  26 *
  27 * User space visible behavior:
  28 * - FIFO ordering for semop() operations (just FIFO, not starvation
  29 *   protection)
  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
  33 *   SETALL calls.
  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.
  40 *
  41 * Internals:
  42 * - scalability:
  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
  51 *   count_semzcnt()
  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.
  74 */
  75
  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>
  89
  90#include <asm/uaccess.h>
  91#include "util.h"
  92
  93/* One semaphore structure for each semaphore in the system. */
  94struct sem {
  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;
 104
 105/* One queue for each sleeping process in the system. */
 106struct sem_queue {
 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? */
 115};
 116
 117/* Each task has a list of undo requests. They are executed automatically
 118 * when the process exits.
 119 */
 120struct sem_undo {
 121        struct list_head        list_proc;      /* per-process list: *
 122                                                 * all undos from one process
 123                                                 * rcu protected */
 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 */
 131};
 132
 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.
 135 */
 136struct sem_undo_list {
 137        atomic_t                refcnt;
 138        spinlock_t              lock;
 139        struct list_head        list_proc;
 140};
 141
 142
 143#define sem_ids(ns)     ((ns)->ids[IPC_SEM_IDS])
 144
 145#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
 146
 147static int newary(struct ipc_namespace *, struct ipc_params *);
 148static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
 149#ifdef CONFIG_PROC_FS
 150static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
 151#endif
 152
 153#define SEMMSL_FAST     256 /* 512 bytes on stack */
 154#define SEMOPM_FAST     64  /* ~ 372 bytes on stack */
 155
 156/*
 157 * Locking:
 158 *      sem_undo.id_next,
 159 *      sem_array.complex_count,
 160 *      sem_array.pending{_alter,_cont},
 161 *      sem_array.sem_undo: global sem_lock() for read/write
 162 *      sem_undo.proc_next: only "current" is allowed to read/write that field.
 163 *      
 164 *      sem_array.sem_base[i].pending_{const,alter}:
 165 *              global or semaphore sem_lock() for read/write
 166 */
 167
 168#define sc_semmsl       sem_ctls[0]
 169#define sc_semmns       sem_ctls[1]
 170#define sc_semopm       sem_ctls[2]
 171#define sc_semmni       sem_ctls[3]
 172
 173void sem_init_ns(struct ipc_namespace *ns)
 174{
 175        ns->sc_semmsl = SEMMSL;
 176        ns->sc_semmns = SEMMNS;
 177        ns->sc_semopm = SEMOPM;
 178        ns->sc_semmni = SEMMNI;
 179        ns->used_sems = 0;
 180        ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
 181}
 182
 183#ifdef CONFIG_IPC_NS
 184void sem_exit_ns(struct ipc_namespace *ns)
 185{
 186        free_ipcs(ns, &sem_ids(ns), freeary);
 187        idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
 188}
 189#endif
 190
 191void __init sem_init (void)
 192{
 193        sem_init_ns(&init_ipc_ns);
 194        ipc_init_proc_interface("sysvipc/sem",
 195                                "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
 196                                IPC_SEM_IDS, sysvipc_sem_proc_show);
 197}
 198
 199/**
 200 * unmerge_queues - unmerge queues, if possible.
 201 * @sma: semaphore array
 202 *
 203 * The function unmerges the wait queues if complex_count is 0.
 204 * It must be called prior to dropping the global semaphore array lock.
 205 */
 206static void unmerge_queues(struct sem_array *sma)
 207{
 208        struct sem_queue *q, *tq;
 209
 210        /* complex operations still around? */
 211        if (sma->complex_count)
 212                return;
 213        /*
 214         * We will switch back to simple mode.
 215         * Move all pending operation back into the per-semaphore
 216         * queues.
 217         */
 218        list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
 219                struct sem *curr;
 220                curr = &sma->sem_base[q->sops[0].sem_num];
 221
 222                list_add_tail(&q->list, &curr->pending_alter);
 223        }
 224        INIT_LIST_HEAD(&sma->pending_alter);
 225}
 226
 227/**
 228 * merge_queues - Merge single semop queues into global queue
 229 * @sma: semaphore array
 230 *
 231 * This function merges all per-semaphore queues into the global queue.
 232 * It is necessary to achieve FIFO ordering for the pending single-sop
 233 * operations when a multi-semop operation must sleep.
 234 * Only the alter operations must be moved, the const operations can stay.
 235 */
 236static void merge_queues(struct sem_array *sma)
 237{
 238        int i;
 239        for (i = 0; i < sma->sem_nsems; i++) {
 240                struct sem *sem = sma->sem_base + i;
 241
 242                list_splice_init(&sem->pending_alter, &sma->pending_alter);
 243        }
 244}
 245
 246static void sem_rcu_free(struct rcu_head *head)
 247{
 248        struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
 249        struct sem_array *sma = ipc_rcu_to_struct(p);
 250
 251        security_sem_free(sma);
 252        ipc_rcu_free(head);
 253}
 254
 255/*
 256 * Wait until all currently ongoing simple ops have completed.
 257 * Caller must own sem_perm.lock.
 258 * New simple ops cannot start, because simple ops first check
 259 * that sem_perm.lock is free.
 260 * that a) sem_perm.lock is free and b) complex_count is 0.
 261 */
 262static void sem_wait_array(struct sem_array *sma)
 263{
 264        int i;
 265        struct sem *sem;
 266
 267        if (sma->complex_count)  {
 268                /* The thread that increased sma->complex_count waited on
 269                 * all sem->lock locks. Thus we don't need to wait again.
 270                 */
 271                return;
 272        }
 273
 274        for (i = 0; i < sma->sem_nsems; i++) {
 275                sem = sma->sem_base + i;
 276                spin_unlock_wait(&sem->lock);
 277        }
 278}
 279
 280/*
 281 * If the request contains only one semaphore operation, and there are
 282 * no complex transactions pending, lock only the semaphore involved.
 283 * Otherwise, lock the entire semaphore array, since we either have
 284 * multiple semaphores in our own semops, or we need to look at
 285 * semaphores from other pending complex operations.
 286 */
 287static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
 288                              int nsops)
 289{
 290        struct sem *sem;
 291
 292        if (nsops != 1) {
 293                /* Complex operation - acquire a full lock */
 294                ipc_lock_object(&sma->sem_perm);
 295
 296                /* And wait until all simple ops that are processed
 297                 * right now have dropped their locks.
 298                 */
 299                sem_wait_array(sma);
 300                return -1;
 301        }
 302
 303        /*
 304         * Only one semaphore affected - try to optimize locking.
 305         * The rules are:
 306         * - optimized locking is possible if no complex operation
 307         *   is either enqueued or processed right now.
 308         * - The test for enqueued complex ops is simple:
 309         *      sma->complex_count != 0
 310         * - Testing for complex ops that are processed right now is
 311         *   a bit more difficult. Complex ops acquire the full lock
 312         *   and first wait that the running simple ops have completed.
 313         *   (see above)
 314         *   Thus: If we own a simple lock and the global lock is free
 315         *      and complex_count is now 0, then it will stay 0 and
 316         *      thus just locking sem->lock is sufficient.
 317         */
 318        sem = sma->sem_base + sops->sem_num;
 319
 320        if (sma->complex_count == 0) {
 321                /*
 322                 * It appears that no complex operation is around.
 323                 * Acquire the per-semaphore lock.
 324                 */
 325                spin_lock(&sem->lock);
 326
 327                /* Then check that the global lock is free */
 328                if (!spin_is_locked(&sma->sem_perm.lock)) {
 329                        /* spin_is_locked() is not a memory barrier */
 330                        smp_mb();
 331
 332                        /* Now repeat the test of complex_count:
 333                         * It can't change anymore until we drop sem->lock.
 334                         * Thus: if is now 0, then it will stay 0.
 335                         */
 336                        if (sma->complex_count == 0) {
 337                                /* fast path successful! */
 338                                return sops->sem_num;
 339                        }
 340                }
 341                spin_unlock(&sem->lock);
 342        }
 343
 344        /* slow path: acquire the full lock */
 345        ipc_lock_object(&sma->sem_perm);
 346
 347        if (sma->complex_count == 0) {
 348                /* False alarm:
 349                 * There is no complex operation, thus we can switch
 350                 * back to the fast path.
 351                 */
 352                spin_lock(&sem->lock);
 353                ipc_unlock_object(&sma->sem_perm);
 354                return sops->sem_num;
 355        } else {
 356                /* Not a false alarm, thus complete the sequence for a
 357                 * full lock.
 358                 */
 359                sem_wait_array(sma);
 360                return -1;
 361        }
 362}
 363
 364static inline void sem_unlock(struct sem_array *sma, int locknum)
 365{
 366        if (locknum == -1) {
 367                unmerge_queues(sma);
 368                ipc_unlock_object(&sma->sem_perm);
 369        } else {
 370                struct sem *sem = sma->sem_base + locknum;
 371                spin_unlock(&sem->lock);
 372        }
 373}
 374
 375/*
 376 * sem_lock_(check_) routines are called in the paths where the rwsem
 377 * is not held.
 378 *
 379 * The caller holds the RCU read lock.
 380 */
 381static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
 382                        int id, struct sembuf *sops, int nsops, int *locknum)
 383{
 384        struct kern_ipc_perm *ipcp;
 385        struct sem_array *sma;
 386
 387        ipcp = ipc_obtain_object(&sem_ids(ns), id);
 388        if (IS_ERR(ipcp))
 389                return ERR_CAST(ipcp);
 390
 391        sma = container_of(ipcp, struct sem_array, sem_perm);
 392        *locknum = sem_lock(sma, sops, nsops);
 393
 394        /* ipc_rmid() may have already freed the ID while sem_lock
 395         * was spinning: verify that the structure is still valid
 396         */
 397        if (!ipcp->deleted)
 398                return container_of(ipcp, struct sem_array, sem_perm);
 399
 400        sem_unlock(sma, *locknum);
 401        return ERR_PTR(-EINVAL);
 402}
 403
 404static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
 405{
 406        struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
 407
 408        if (IS_ERR(ipcp))
 409                return ERR_CAST(ipcp);
 410
 411        return container_of(ipcp, struct sem_array, sem_perm);
 412}
 413
 414static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
 415                                                        int id)
 416{
 417        struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
 418
 419        if (IS_ERR(ipcp))
 420                return ERR_CAST(ipcp);
 421
 422        return container_of(ipcp, struct sem_array, sem_perm);
 423}
 424
 425static inline void sem_lock_and_putref(struct sem_array *sma)
 426{
 427        sem_lock(sma, NULL, -1);
 428        ipc_rcu_putref(sma, ipc_rcu_free);
 429}
 430
 431static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
 432{
 433        ipc_rmid(&sem_ids(ns), &s->sem_perm);
 434}
 435
 436/*
 437 * Lockless wakeup algorithm:
 438 * Without the check/retry algorithm a lockless wakeup is possible:
 439 * - queue.status is initialized to -EINTR before blocking.
 440 * - wakeup is performed by
 441 *      * unlinking the queue entry from the pending list
 442 *      * setting queue.status to IN_WAKEUP
 443 *        This is the notification for the blocked thread that a
 444 *        result value is imminent.
 445 *      * call wake_up_process
 446 *      * set queue.status to the final value.
 447 * - the previously blocked thread checks queue.status:
 448 *      * if it's IN_WAKEUP, then it must wait until the value changes
 449 *      * if it's not -EINTR, then the operation was completed by
 450 *        update_queue. semtimedop can return queue.status without
 451 *        performing any operation on the sem array.
 452 *      * otherwise it must acquire the spinlock and check what's up.
 453 *
 454 * The two-stage algorithm is necessary to protect against the following
 455 * races:
 456 * - if queue.status is set after wake_up_process, then the woken up idle
 457 *   thread could race forward and try (and fail) to acquire sma->lock
 458 *   before update_queue had a chance to set queue.status
 459 * - if queue.status is written before wake_up_process and if the
 460 *   blocked process is woken up by a signal between writing
 461 *   queue.status and the wake_up_process, then the woken up
 462 *   process could return from semtimedop and die by calling
 463 *   sys_exit before wake_up_process is called. Then wake_up_process
 464 *   will oops, because the task structure is already invalid.
 465 *   (yes, this happened on s390 with sysv msg).
 466 *
 467 */
 468#define IN_WAKEUP       1
 469
 470/**
 471 * newary - Create a new semaphore set
 472 * @ns: namespace
 473 * @params: ptr to the structure that contains key, semflg and nsems
 474 *
 475 * Called with sem_ids.rwsem held (as a writer)
 476 */
 477
 478static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 479{
 480        int id;
 481        int retval;
 482        struct sem_array *sma;
 483        int size;
 484        key_t key = params->key;
 485        int nsems = params->u.nsems;
 486        int semflg = params->flg;
 487        int i;
 488
 489        if (!nsems)
 490                return -EINVAL;
 491        if (ns->used_sems + nsems > ns->sc_semmns)
 492                return -ENOSPC;
 493
 494        size = sizeof (*sma) + nsems * sizeof (struct sem);
 495        sma = ipc_rcu_alloc(size);
 496        if (!sma) {
 497                return -ENOMEM;
 498        }
 499        memset (sma, 0, size);
 500
 501        sma->sem_perm.mode = (semflg & S_IRWXUGO);
 502        sma->sem_perm.key = key;
 503
 504        sma->sem_perm.security = NULL;
 505        retval = security_sem_alloc(sma);
 506        if (retval) {
 507                ipc_rcu_putref(sma, ipc_rcu_free);
 508                return retval;
 509        }
 510
 511        id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 512        if (id < 0) {
 513                ipc_rcu_putref(sma, sem_rcu_free);
 514                return id;
 515        }
 516        ns->used_sems += nsems;
 517
 518        sma->sem_base = (struct sem *) &sma[1];
 519
 520        for (i = 0; i < nsems; i++) {
 521                INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
 522                INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
 523                spin_lock_init(&sma->sem_base[i].lock);
 524        }
 525
 526        sma->complex_count = 0;
 527        INIT_LIST_HEAD(&sma->pending_alter);
 528        INIT_LIST_HEAD(&sma->pending_const);
 529        INIT_LIST_HEAD(&sma->list_id);
 530        sma->sem_nsems = nsems;
 531        sma->sem_ctime = get_seconds();
 532        sem_unlock(sma, -1);
 533        rcu_read_unlock();
 534
 535        return sma->sem_perm.id;
 536}
 537
 538
 539/*
 540 * Called with sem_ids.rwsem and ipcp locked.
 541 */
 542static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
 543{
 544        struct sem_array *sma;
 545
 546        sma = container_of(ipcp, struct sem_array, sem_perm);
 547        return security_sem_associate(sma, semflg);
 548}
 549
 550/*
 551 * Called with sem_ids.rwsem and ipcp locked.
 552 */
 553static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
 554                                struct ipc_params *params)
 555{
 556        struct sem_array *sma;
 557
 558        sma = container_of(ipcp, struct sem_array, sem_perm);
 559        if (params->u.nsems > sma->sem_nsems)
 560                return -EINVAL;
 561
 562        return 0;
 563}
 564
 565SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
 566{
 567        struct ipc_namespace *ns;
 568        struct ipc_ops sem_ops;
 569        struct ipc_params sem_params;
 570
 571        ns = current->nsproxy->ipc_ns;
 572
 573        if (nsems < 0 || nsems > ns->sc_semmsl)
 574                return -EINVAL;
 575
 576        sem_ops.getnew = newary;
 577        sem_ops.associate = sem_security;
 578        sem_ops.more_checks = sem_more_checks;
 579
 580        sem_params.key = key;
 581        sem_params.flg = semflg;
 582        sem_params.u.nsems = nsems;
 583
 584        return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
 585}
 586
 587/** perform_atomic_semop - Perform (if possible) a semaphore operation
 588 * @sma: semaphore array
 589 * @sops: array with operations that should be checked
 590 * @nsems: number of sops
 591 * @un: undo array
 592 * @pid: pid that did the change
 593 *
 594 * Returns 0 if the operation was possible.
 595 * Returns 1 if the operation is impossible, the caller must sleep.
 596 * Negative values are error codes.
 597 */
 598
 599static int perform_atomic_semop(struct sem_array *sma, struct sembuf *sops,
 600                             int nsops, struct sem_undo *un, int pid)
 601{
 602        int result, sem_op;
 603        struct sembuf *sop;
 604        struct sem * curr;
 605
 606        for (sop = sops; sop < sops + nsops; sop++) {
 607                curr = sma->sem_base + sop->sem_num;
 608                sem_op = sop->sem_op;
 609                result = curr->semval;
 610  
 611                if (!sem_op && result)
 612                        goto would_block;
 613
 614                result += sem_op;
 615                if (result < 0)
 616                        goto would_block;
 617                if (result > SEMVMX)
 618                        goto out_of_range;
 619                if (sop->sem_flg & SEM_UNDO) {
 620                        int undo = un->semadj[sop->sem_num] - sem_op;
 621                        /*
 622                         *      Exceeding the undo range is an error.
 623                         */
 624                        if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 625                                goto out_of_range;
 626                }
 627                curr->semval = result;
 628        }
 629
 630        sop--;
 631        while (sop >= sops) {
 632                sma->sem_base[sop->sem_num].sempid = pid;
 633                if (sop->sem_flg & SEM_UNDO)
 634                        un->semadj[sop->sem_num] -= sop->sem_op;
 635                sop--;
 636        }
 637        
 638        return 0;
 639
 640out_of_range:
 641        result = -ERANGE;
 642        goto undo;
 643
 644would_block:
 645        if (sop->sem_flg & IPC_NOWAIT)
 646                result = -EAGAIN;
 647        else
 648                result = 1;
 649
 650undo:
 651        sop--;
 652        while (sop >= sops) {
 653                sma->sem_base[sop->sem_num].semval -= sop->sem_op;
 654                sop--;
 655        }
 656
 657        return result;
 658}
 659
 660/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
 661 * @q: queue entry that must be signaled
 662 * @error: Error value for the signal
 663 *
 664 * Prepare the wake-up of the queue entry q.
 665 */
 666static void wake_up_sem_queue_prepare(struct list_head *pt,
 667                                struct sem_queue *q, int error)
 668{
 669        if (list_empty(pt)) {
 670                /*
 671                 * Hold preempt off so that we don't get preempted and have the
 672                 * wakee busy-wait until we're scheduled back on.
 673                 */
 674                preempt_disable();
 675        }
 676        q->status = IN_WAKEUP;
 677        q->pid = error;
 678
 679        list_add_tail(&q->list, pt);
 680}
 681
 682/**
 683 * wake_up_sem_queue_do(pt) - do the actual wake-up
 684 * @pt: list of tasks to be woken up
 685 *
 686 * Do the actual wake-up.
 687 * The function is called without any locks held, thus the semaphore array
 688 * could be destroyed already and the tasks can disappear as soon as the
 689 * status is set to the actual return code.
 690 */
 691static void wake_up_sem_queue_do(struct list_head *pt)
 692{
 693        struct sem_queue *q, *t;
 694        int did_something;
 695
 696        did_something = !list_empty(pt);
 697        list_for_each_entry_safe(q, t, pt, list) {
 698                wake_up_process(q->sleeper);
 699                /* q can disappear immediately after writing q->status. */
 700                smp_wmb();
 701                q->status = q->pid;
 702        }
 703        if (did_something)
 704                preempt_enable();
 705}
 706
 707static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
 708{
 709        list_del(&q->list);
 710        if (q->nsops > 1)
 711                sma->complex_count--;
 712}
 713
 714/** check_restart(sma, q)
 715 * @sma: semaphore array
 716 * @q: the operation that just completed
 717 *
 718 * update_queue is O(N^2) when it restarts scanning the whole queue of
 719 * waiting operations. Therefore this function checks if the restart is
 720 * really necessary. It is called after a previously waiting operation
 721 * modified the array.
 722 * Note that wait-for-zero operations are handled without restart.
 723 */
 724static int check_restart(struct sem_array *sma, struct sem_queue *q)
 725{
 726        /* pending complex alter operations are too difficult to analyse */
 727        if (!list_empty(&sma->pending_alter))
 728                return 1;
 729
 730        /* we were a sleeping complex operation. Too difficult */
 731        if (q->nsops > 1)
 732                return 1;
 733
 734        /* It is impossible that someone waits for the new value:
 735         * - complex operations always restart.
 736         * - wait-for-zero are handled seperately.
 737         * - q is a previously sleeping simple operation that
 738         *   altered the array. It must be a decrement, because
 739         *   simple increments never sleep.
 740         * - If there are older (higher priority) decrements
 741         *   in the queue, then they have observed the original
 742         *   semval value and couldn't proceed. The operation
 743         *   decremented to value - thus they won't proceed either.
 744         */
 745        return 0;
 746}
 747
 748/**
 749 * wake_const_ops(sma, semnum, pt) - Wake up non-alter tasks
 750 * @sma: semaphore array.
 751 * @semnum: semaphore that was modified.
 752 * @pt: list head for the tasks that must be woken up.
 753 *
 754 * wake_const_ops must be called after a semaphore in a semaphore array
 755 * was set to 0. If complex const operations are pending, wake_const_ops must
 756 * be called with semnum = -1, as well as with the number of each modified
 757 * semaphore.
 758 * The tasks that must be woken up are added to @pt. The return code
 759 * is stored in q->pid.
 760 * The function returns 1 if at least one operation was completed successfully.
 761 */
 762static int wake_const_ops(struct sem_array *sma, int semnum,
 763                                struct list_head *pt)
 764{
 765        struct sem_queue *q;
 766        struct list_head *walk;
 767        struct list_head *pending_list;
 768        int semop_completed = 0;
 769
 770        if (semnum == -1)
 771                pending_list = &sma->pending_const;
 772        else
 773                pending_list = &sma->sem_base[semnum].pending_const;
 774
 775        walk = pending_list->next;
 776        while (walk != pending_list) {
 777                int error;
 778
 779                q = container_of(walk, struct sem_queue, list);
 780                walk = walk->next;
 781
 782                error = perform_atomic_semop(sma, q->sops, q->nsops,
 783                                                 q->undo, q->pid);
 784
 785                if (error <= 0) {
 786                        /* operation completed, remove from queue & wakeup */
 787
 788                        unlink_queue(sma, q);
 789
 790                        wake_up_sem_queue_prepare(pt, q, error);
 791                        if (error == 0)
 792                                semop_completed = 1;
 793                }
 794        }
 795        return semop_completed;
 796}
 797
 798/**
 799 * do_smart_wakeup_zero(sma, sops, nsops, pt) - wakeup all wait for zero tasks
 800 * @sma: semaphore array
 801 * @sops: operations that were performed
 802 * @nsops: number of operations
 803 * @pt: list head of the tasks that must be woken up.
 804 *
 805 * do_smart_wakeup_zero() checks all required queue for wait-for-zero
 806 * operations, based on the actual changes that were performed on the
 807 * semaphore array.
 808 * The function returns 1 if at least one operation was completed successfully.
 809 */
 810static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
 811                                        int nsops, struct list_head *pt)
 812{
 813        int i;
 814        int semop_completed = 0;
 815        int got_zero = 0;
 816
 817        /* first: the per-semaphore queues, if known */
 818        if (sops) {
 819                for (i = 0; i < nsops; i++) {
 820                        int num = sops[i].sem_num;
 821
 822                        if (sma->sem_base[num].semval == 0) {
 823                                got_zero = 1;
 824                                semop_completed |= wake_const_ops(sma, num, pt);
 825                        }
 826                }
 827        } else {
 828                /*
 829                 * No sops means modified semaphores not known.
 830                 * Assume all were changed.
 831                 */
 832                for (i = 0; i < sma->sem_nsems; i++) {
 833                        if (sma->sem_base[i].semval == 0) {
 834                                got_zero = 1;
 835                                semop_completed |= wake_const_ops(sma, i, pt);
 836                        }
 837                }
 838        }
 839        /*
 840         * If one of the modified semaphores got 0,
 841         * then check the global queue, too.
 842         */
 843        if (got_zero)
 844                semop_completed |= wake_const_ops(sma, -1, pt);
 845
 846        return semop_completed;
 847}
 848
 849
 850/**
 851 * update_queue(sma, semnum): Look for tasks that can be completed.
 852 * @sma: semaphore array.
 853 * @semnum: semaphore that was modified.
 854 * @pt: list head for the tasks that must be woken up.
 855 *
 856 * update_queue must be called after a semaphore in a semaphore array
 857 * was modified. If multiple semaphores were modified, update_queue must
 858 * be called with semnum = -1, as well as with the number of each modified
 859 * semaphore.
 860 * The tasks that must be woken up are added to @pt. The return code
 861 * is stored in q->pid.
 862 * The function internally checks if const operations can now succeed.
 863 *
 864 * The function return 1 if at least one semop was completed successfully.
 865 */
 866static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
 867{
 868        struct sem_queue *q;
 869        struct list_head *walk;
 870        struct list_head *pending_list;
 871        int semop_completed = 0;
 872
 873        if (semnum == -1)
 874                pending_list = &sma->pending_alter;
 875        else
 876                pending_list = &sma->sem_base[semnum].pending_alter;
 877
 878again:
 879        walk = pending_list->next;
 880        while (walk != pending_list) {
 881                int error, restart;
 882
 883                q = container_of(walk, struct sem_queue, list);
 884                walk = walk->next;
 885
 886                /* If we are scanning the single sop, per-semaphore list of
 887                 * one semaphore and that semaphore is 0, then it is not
 888                 * necessary to scan further: simple increments
 889                 * that affect only one entry succeed immediately and cannot
 890                 * be in the  per semaphore pending queue, and decrements
 891                 * cannot be successful if the value is already 0.
 892                 */
 893                if (semnum != -1 && sma->sem_base[semnum].semval == 0)
 894                        break;
 895
 896                error = perform_atomic_semop(sma, q->sops, q->nsops,
 897                                         q->undo, q->pid);
 898
 899                /* Does q->sleeper still need to sleep? */
 900                if (error > 0)
 901                        continue;
 902
 903                unlink_queue(sma, q);
 904
 905                if (error) {
 906                        restart = 0;
 907                } else {
 908                        semop_completed = 1;
 909                        do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
 910                        restart = check_restart(sma, q);
 911                }
 912
 913                wake_up_sem_queue_prepare(pt, q, error);
 914                if (restart)
 915                        goto again;
 916        }
 917        return semop_completed;
 918}
 919
 920/**
 921 * set_semotime(sma, sops) - set sem_otime
 922 * @sma: semaphore array
 923 * @sops: operations that modified the array, may be NULL
 924 *
 925 * sem_otime is replicated to avoid cache line trashing.
 926 * This function sets one instance to the current time.
 927 */
 928static void set_semotime(struct sem_array *sma, struct sembuf *sops)
 929{
 930        if (sops == NULL) {
 931                sma->sem_base[0].sem_otime = get_seconds();
 932        } else {
 933                sma->sem_base[sops[0].sem_num].sem_otime =
 934                                                        get_seconds();
 935        }
 936}
 937
 938/**
 939 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
 940 * @sma: semaphore array
 941 * @sops: operations that were performed
 942 * @nsops: number of operations
 943 * @otime: force setting otime
 944 * @pt: list head of the tasks that must be woken up.
 945 *
 946 * do_smart_update() does the required calls to update_queue and wakeup_zero,
 947 * based on the actual changes that were performed on the semaphore array.
 948 * Note that the function does not do the actual wake-up: the caller is
 949 * responsible for calling wake_up_sem_queue_do(@pt).
 950 * It is safe to perform this call after dropping all locks.
 951 */
 952static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
 953                        int otime, struct list_head *pt)
 954{
 955        int i;
 956
 957        otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
 958
 959        if (!list_empty(&sma->pending_alter)) {
 960                /* semaphore array uses the global queue - just process it. */
 961                otime |= update_queue(sma, -1, pt);
 962        } else {
 963                if (!sops) {
 964                        /*
 965                         * No sops, thus the modified semaphores are not
 966                         * known. Check all.
 967                         */
 968                        for (i = 0; i < sma->sem_nsems; i++)
 969                                otime |= update_queue(sma, i, pt);
 970                } else {
 971                        /*
 972                         * Check the semaphores that were increased:
 973                         * - No complex ops, thus all sleeping ops are
 974                         *   decrease.
 975                         * - if we decreased the value, then any sleeping
 976                         *   semaphore ops wont be able to run: If the
 977                         *   previous value was too small, then the new
 978                         *   value will be too small, too.
 979                         */
 980                        for (i = 0; i < nsops; i++) {
 981                                if (sops[i].sem_op > 0) {
 982                                        otime |= update_queue(sma,
 983                                                        sops[i].sem_num, pt);
 984                                }
 985                        }
 986                }
 987        }
 988        if (otime)
 989                set_semotime(sma, sops);
 990}
 991
 992/* The following counts are associated to each semaphore:
 993 *   semncnt        number of tasks waiting on semval being nonzero
 994 *   semzcnt        number of tasks waiting on semval being zero
 995 * This model assumes that a task waits on exactly one semaphore.
 996 * Since semaphore operations are to be performed atomically, tasks actually
 997 * wait on a whole sequence of semaphores simultaneously.
 998 * The counts we return here are a rough approximation, but still
 999 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
1000 */
1001static int count_semncnt (struct sem_array * sma, ushort semnum)
1002{
1003        int semncnt;
1004        struct sem_queue * q;
1005
1006        semncnt = 0;
1007        list_for_each_entry(q, &sma->sem_base[semnum].pending_alter, list) {
1008                struct sembuf * sops = q->sops;
1009                BUG_ON(sops->sem_num != semnum);
1010                if ((sops->sem_op < 0) && !(sops->sem_flg & IPC_NOWAIT))
1011                        semncnt++;
1012        }
1013
1014        list_for_each_entry(q, &sma->pending_alter, list) {
1015                struct sembuf * sops = q->sops;
1016                int nsops = q->nsops;
1017                int i;
1018                for (i = 0; i < nsops; i++)
1019                        if (sops[i].sem_num == semnum
1020                            && (sops[i].sem_op < 0)
1021                            && !(sops[i].sem_flg & IPC_NOWAIT))
1022                                semncnt++;
1023        }
1024        return semncnt;
1025}
1026
1027static int count_semzcnt (struct sem_array * sma, ushort semnum)
1028{
1029        int semzcnt;
1030        struct sem_queue * q;
1031
1032        semzcnt = 0;
1033        list_for_each_entry(q, &sma->sem_base[semnum].pending_const, list) {
1034                struct sembuf * sops = q->sops;
1035                BUG_ON(sops->sem_num != semnum);
1036                if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
1037                        semzcnt++;
1038        }
1039
1040        list_for_each_entry(q, &sma->pending_const, list) {
1041                struct sembuf * sops = q->sops;
1042                int nsops = q->nsops;
1043                int i;
1044                for (i = 0; i < nsops; i++)
1045                        if (sops[i].sem_num == semnum
1046                            && (sops[i].sem_op == 0)
1047                            && !(sops[i].sem_flg & IPC_NOWAIT))
1048                                semzcnt++;
1049        }
1050        return semzcnt;
1051}
1052
1053/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1054 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1055 * remains locked on exit.
1056 */
1057static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1058{
1059        struct sem_undo *un, *tu;
1060        struct sem_queue *q, *tq;
1061        struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1062        struct list_head tasks;
1063        int i;
1064
1065        /* Free the existing undo structures for this semaphore set.  */
1066        ipc_assert_locked_object(&sma->sem_perm);
1067        list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1068                list_del(&un->list_id);
1069                spin_lock(&un->ulp->lock);
1070                un->semid = -1;
1071                list_del_rcu(&un->list_proc);
1072                spin_unlock(&un->ulp->lock);
1073                kfree_rcu(un, rcu);
1074        }
1075
1076        /* Wake up all pending processes and let them fail with EIDRM. */
1077        INIT_LIST_HEAD(&tasks);
1078        list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1079                unlink_queue(sma, q);
1080                wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1081        }
1082
1083        list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1084                unlink_queue(sma, q);
1085                wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1086        }
1087        for (i = 0; i < sma->sem_nsems; i++) {
1088                struct sem *sem = sma->sem_base + i;
1089                list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1090                        unlink_queue(sma, q);
1091                        wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1092                }
1093                list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1094                        unlink_queue(sma, q);
1095                        wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1096                }
1097        }
1098
1099        /* Remove the semaphore set from the IDR */
1100        sem_rmid(ns, sma);
1101        sem_unlock(sma, -1);
1102        rcu_read_unlock();
1103
1104        wake_up_sem_queue_do(&tasks);
1105        ns->used_sems -= sma->sem_nsems;
1106        ipc_rcu_putref(sma, sem_rcu_free);
1107}
1108
1109static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1110{
1111        switch(version) {
1112        case IPC_64:
1113                return copy_to_user(buf, in, sizeof(*in));
1114        case IPC_OLD:
1115            {
1116                struct semid_ds out;
1117
1118                memset(&out, 0, sizeof(out));
1119
1120                ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1121
1122                out.sem_otime   = in->sem_otime;
1123                out.sem_ctime   = in->sem_ctime;
1124                out.sem_nsems   = in->sem_nsems;
1125
1126                return copy_to_user(buf, &out, sizeof(out));
1127            }
1128        default:
1129                return -EINVAL;
1130        }
1131}
1132
1133static time_t get_semotime(struct sem_array *sma)
1134{
1135        int i;
1136        time_t res;
1137
1138        res = sma->sem_base[0].sem_otime;
1139        for (i = 1; i < sma->sem_nsems; i++) {
1140                time_t to = sma->sem_base[i].sem_otime;
1141
1142                if (to > res)
1143                        res = to;
1144        }
1145        return res;
1146}
1147
1148static int semctl_nolock(struct ipc_namespace *ns, int semid,
1149                         int cmd, int version, void __user *p)
1150{
1151        int err;
1152        struct sem_array *sma;
1153
1154        switch(cmd) {
1155        case IPC_INFO:
1156        case SEM_INFO:
1157        {
1158                struct seminfo seminfo;
1159                int max_id;
1160
1161                err = security_sem_semctl(NULL, cmd);
1162                if (err)
1163                        return err;
1164                
1165                memset(&seminfo,0,sizeof(seminfo));
1166                seminfo.semmni = ns->sc_semmni;
1167                seminfo.semmns = ns->sc_semmns;
1168                seminfo.semmsl = ns->sc_semmsl;
1169                seminfo.semopm = ns->sc_semopm;
1170                seminfo.semvmx = SEMVMX;
1171                seminfo.semmnu = SEMMNU;
1172                seminfo.semmap = SEMMAP;
1173                seminfo.semume = SEMUME;
1174                down_read(&sem_ids(ns).rwsem);
1175                if (cmd == SEM_INFO) {
1176                        seminfo.semusz = sem_ids(ns).in_use;
1177                        seminfo.semaem = ns->used_sems;
1178                } else {
1179                        seminfo.semusz = SEMUSZ;
1180                        seminfo.semaem = SEMAEM;
1181                }
1182                max_id = ipc_get_maxid(&sem_ids(ns));
1183                up_read(&sem_ids(ns).rwsem);
1184                if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) 
1185                        return -EFAULT;
1186                return (max_id < 0) ? 0: max_id;
1187        }
1188        case IPC_STAT:
1189        case SEM_STAT:
1190        {
1191                struct semid64_ds tbuf;
1192                int id = 0;
1193
1194                memset(&tbuf, 0, sizeof(tbuf));
1195
1196                rcu_read_lock();
1197                if (cmd == SEM_STAT) {
1198                        sma = sem_obtain_object(ns, semid);
1199                        if (IS_ERR(sma)) {
1200                                err = PTR_ERR(sma);
1201                                goto out_unlock;
1202                        }
1203                        id = sma->sem_perm.id;
1204                } else {
1205                        sma = sem_obtain_object_check(ns, semid);
1206                        if (IS_ERR(sma)) {
1207                                err = PTR_ERR(sma);
1208                                goto out_unlock;
1209                        }
1210                }
1211
1212                err = -EACCES;
1213                if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1214                        goto out_unlock;
1215
1216                err = security_sem_semctl(sma, cmd);
1217                if (err)
1218                        goto out_unlock;
1219
1220                kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1221                tbuf.sem_otime = get_semotime(sma);
1222                tbuf.sem_ctime = sma->sem_ctime;
1223                tbuf.sem_nsems = sma->sem_nsems;
1224                rcu_read_unlock();
1225                if (copy_semid_to_user(p, &tbuf, version))
1226                        return -EFAULT;
1227                return id;
1228        }
1229        default:
1230                return -EINVAL;
1231        }
1232out_unlock:
1233        rcu_read_unlock();
1234        return err;
1235}
1236
1237static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1238                unsigned long arg)
1239{
1240        struct sem_undo *un;
1241        struct sem_array *sma;
1242        struct sem* curr;
1243        int err;
1244        struct list_head tasks;
1245        int val;
1246#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1247        /* big-endian 64bit */
1248        val = arg >> 32;
1249#else
1250        /* 32bit or little-endian 64bit */
1251        val = arg;
1252#endif
1253
1254        if (val > SEMVMX || val < 0)
1255                return -ERANGE;
1256
1257        INIT_LIST_HEAD(&tasks);
1258
1259        rcu_read_lock();
1260        sma = sem_obtain_object_check(ns, semid);
1261        if (IS_ERR(sma)) {
1262                rcu_read_unlock();
1263                return PTR_ERR(sma);
1264        }
1265
1266        if (semnum < 0 || semnum >= sma->sem_nsems) {
1267                rcu_read_unlock();
1268                return -EINVAL;
1269        }
1270
1271
1272        if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1273                rcu_read_unlock();
1274                return -EACCES;
1275        }
1276
1277        err = security_sem_semctl(sma, SETVAL);
1278        if (err) {
1279                rcu_read_unlock();
1280                return -EACCES;
1281        }
1282
1283        sem_lock(sma, NULL, -1);
1284
1285        if (sma->sem_perm.deleted) {
1286                sem_unlock(sma, -1);
1287                rcu_read_unlock();
1288                return -EIDRM;
1289        }
1290
1291        curr = &sma->sem_base[semnum];
1292
1293        ipc_assert_locked_object(&sma->sem_perm);
1294        list_for_each_entry(un, &sma->list_id, list_id)
1295                un->semadj[semnum] = 0;
1296
1297        curr->semval = val;
1298        curr->sempid = task_tgid_vnr(current);
1299        sma->sem_ctime = get_seconds();
1300        /* maybe some queued-up processes were waiting for this */
1301        do_smart_update(sma, NULL, 0, 0, &tasks);
1302        sem_unlock(sma, -1);
1303        rcu_read_unlock();
1304        wake_up_sem_queue_do(&tasks);
1305        return 0;
1306}
1307
1308static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1309                int cmd, void __user *p)
1310{
1311        struct sem_array *sma;
1312        struct sem* curr;
1313        int err, nsems;
1314        ushort fast_sem_io[SEMMSL_FAST];
1315        ushort* sem_io = fast_sem_io;
1316        struct list_head tasks;
1317
1318        INIT_LIST_HEAD(&tasks);
1319
1320        rcu_read_lock();
1321        sma = sem_obtain_object_check(ns, semid);
1322        if (IS_ERR(sma)) {
1323                rcu_read_unlock();
1324                return PTR_ERR(sma);
1325        }
1326
1327        nsems = sma->sem_nsems;
1328
1329        err = -EACCES;
1330        if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1331                goto out_rcu_wakeup;
1332
1333        err = security_sem_semctl(sma, cmd);
1334        if (err)
1335                goto out_rcu_wakeup;
1336
1337        err = -EACCES;
1338        switch (cmd) {
1339        case GETALL:
1340        {
1341                ushort __user *array = p;
1342                int i;
1343
1344                sem_lock(sma, NULL, -1);
1345                if (sma->sem_perm.deleted) {
1346                        err = -EIDRM;
1347                        goto out_unlock;
1348                }
1349                if(nsems > SEMMSL_FAST) {
1350                        if (!ipc_rcu_getref(sma)) {
1351                                err = -EIDRM;
1352                                goto out_unlock;
1353                        }
1354                        sem_unlock(sma, -1);
1355                        rcu_read_unlock();
1356                        sem_io = ipc_alloc(sizeof(ushort)*nsems);
1357                        if(sem_io == NULL) {
1358                                ipc_rcu_putref(sma, ipc_rcu_free);
1359                                return -ENOMEM;
1360                        }
1361
1362                        rcu_read_lock();
1363                        sem_lock_and_putref(sma);
1364                        if (sma->sem_perm.deleted) {
1365                                err = -EIDRM;
1366                                goto out_unlock;
1367                        }
1368                }
1369                for (i = 0; i < sma->sem_nsems; i++)
1370                        sem_io[i] = sma->sem_base[i].semval;
1371                sem_unlock(sma, -1);
1372                rcu_read_unlock();
1373                err = 0;
1374                if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1375                        err = -EFAULT;
1376                goto out_free;
1377        }
1378        case SETALL:
1379        {
1380                int i;
1381                struct sem_undo *un;
1382
1383                if (!ipc_rcu_getref(sma)) {
1384                        err = -EIDRM;
1385                        goto out_rcu_wakeup;
1386                }
1387                rcu_read_unlock();
1388
1389                if(nsems > SEMMSL_FAST) {
1390                        sem_io = ipc_alloc(sizeof(ushort)*nsems);
1391                        if(sem_io == NULL) {
1392                                ipc_rcu_putref(sma, ipc_rcu_free);
1393                                return -ENOMEM;
1394                        }
1395                }
1396
1397                if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) {
1398                        ipc_rcu_putref(sma, ipc_rcu_free);
1399                        err = -EFAULT;
1400                        goto out_free;
1401                }
1402
1403                for (i = 0; i < nsems; i++) {
1404                        if (sem_io[i] > SEMVMX) {
1405                                ipc_rcu_putref(sma, ipc_rcu_free);
1406                                err = -ERANGE;
1407                                goto out_free;
1408                        }
1409                }
1410                rcu_read_lock();
1411                sem_lock_and_putref(sma);
1412                if (sma->sem_perm.deleted) {
1413                        err = -EIDRM;
1414                        goto out_unlock;
1415                }
1416
1417                for (i = 0; i < nsems; i++)
1418                        sma->sem_base[i].semval = sem_io[i];
1419
1420                ipc_assert_locked_object(&sma->sem_perm);
1421                list_for_each_entry(un, &sma->list_id, list_id) {
1422                        for (i = 0; i < nsems; i++)
1423                                un->semadj[i] = 0;
1424                }
1425                sma->sem_ctime = get_seconds();
1426                /* maybe some queued-up processes were waiting for this */
1427                do_smart_update(sma, NULL, 0, 0, &tasks);
1428                err = 0;
1429                goto out_unlock;
1430        }
1431        /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1432        }
1433        err = -EINVAL;
1434        if (semnum < 0 || semnum >= nsems)
1435                goto out_rcu_wakeup;
1436
1437        sem_lock(sma, NULL, -1);
1438        if (sma->sem_perm.deleted) {
1439                err = -EIDRM;
1440                goto out_unlock;
1441        }
1442        curr = &sma->sem_base[semnum];
1443
1444        switch (cmd) {
1445        case GETVAL:
1446                err = curr->semval;
1447                goto out_unlock;
1448        case GETPID:
1449                err = curr->sempid;
1450                goto out_unlock;
1451        case GETNCNT:
1452                err = count_semncnt(sma,semnum);
1453                goto out_unlock;
1454        case GETZCNT:
1455                err = count_semzcnt(sma,semnum);
1456                goto out_unlock;
1457        }
1458
1459out_unlock:
1460        sem_unlock(sma, -1);
1461out_rcu_wakeup:
1462        rcu_read_unlock();
1463        wake_up_sem_queue_do(&tasks);
1464out_free:
1465        if(sem_io != fast_sem_io)
1466                ipc_free(sem_io, sizeof(ushort)*nsems);
1467        return err;
1468}
1469
1470static inline unsigned long
1471copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1472{
1473        switch(version) {
1474        case IPC_64:
1475                if (copy_from_user(out, buf, sizeof(*out)))
1476                        return -EFAULT;
1477                return 0;
1478        case IPC_OLD:
1479            {
1480                struct semid_ds tbuf_old;
1481
1482                if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1483                        return -EFAULT;
1484
1485                out->sem_perm.uid       = tbuf_old.sem_perm.uid;
1486                out->sem_perm.gid       = tbuf_old.sem_perm.gid;
1487                out->sem_perm.mode      = tbuf_old.sem_perm.mode;
1488
1489                return 0;
1490            }
1491        default:
1492                return -EINVAL;
1493        }
1494}
1495
1496/*
1497 * This function handles some semctl commands which require the rwsem
1498 * to be held in write mode.
1499 * NOTE: no locks must be held, the rwsem is taken inside this function.
1500 */
1501static int semctl_down(struct ipc_namespace *ns, int semid,
1502                       int cmd, int version, void __user *p)
1503{
1504        struct sem_array *sma;
1505        int err;
1506        struct semid64_ds semid64;
1507        struct kern_ipc_perm *ipcp;
1508
1509        if(cmd == IPC_SET) {
1510                if (copy_semid_from_user(&semid64, p, version))
1511                        return -EFAULT;
1512        }
1513
1514        down_write(&sem_ids(ns).rwsem);
1515        rcu_read_lock();
1516
1517        ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1518                                      &semid64.sem_perm, 0);
1519        if (IS_ERR(ipcp)) {
1520                err = PTR_ERR(ipcp);
1521                goto out_unlock1;
1522        }
1523
1524        sma = container_of(ipcp, struct sem_array, sem_perm);
1525
1526        err = security_sem_semctl(sma, cmd);
1527        if (err)
1528                goto out_unlock1;
1529
1530        switch (cmd) {
1531        case IPC_RMID:
1532                sem_lock(sma, NULL, -1);
1533                /* freeary unlocks the ipc object and rcu */
1534                freeary(ns, ipcp);
1535                goto out_up;
1536        case IPC_SET:
1537                sem_lock(sma, NULL, -1);
1538                err = ipc_update_perm(&semid64.sem_perm, ipcp);
1539                if (err)
1540                        goto out_unlock0;
1541                sma->sem_ctime = get_seconds();
1542                break;
1543        default:
1544                err = -EINVAL;
1545                goto out_unlock1;
1546        }
1547
1548out_unlock0:
1549        sem_unlock(sma, -1);
1550out_unlock1:
1551        rcu_read_unlock();
1552out_up:
1553        up_write(&sem_ids(ns).rwsem);
1554        return err;
1555}
1556
1557SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1558{
1559        int version;
1560        struct ipc_namespace *ns;
1561        void __user *p = (void __user *)arg;
1562
1563        if (semid < 0)
1564                return -EINVAL;
1565
1566        version = ipc_parse_version(&cmd);
1567        ns = current->nsproxy->ipc_ns;
1568
1569        switch(cmd) {
1570        case IPC_INFO:
1571        case SEM_INFO:
1572        case IPC_STAT:
1573        case SEM_STAT:
1574                return semctl_nolock(ns, semid, cmd, version, p);
1575        case GETALL:
1576        case GETVAL:
1577        case GETPID:
1578        case GETNCNT:
1579        case GETZCNT:
1580        case SETALL:
1581                return semctl_main(ns, semid, semnum, cmd, p);
1582        case SETVAL:
1583                return semctl_setval(ns, semid, semnum, arg);
1584        case IPC_RMID:
1585        case IPC_SET:
1586                return semctl_down(ns, semid, cmd, version, p);
1587        default:
1588                return -EINVAL;
1589        }
1590}
1591
1592/* If the task doesn't already have a undo_list, then allocate one
1593 * here.  We guarantee there is only one thread using this undo list,
1594 * and current is THE ONE
1595 *
1596 * If this allocation and assignment succeeds, but later
1597 * portions of this code fail, there is no need to free the sem_undo_list.
1598 * Just let it stay associated with the task, and it'll be freed later
1599 * at exit time.
1600 *
1601 * This can block, so callers must hold no locks.
1602 */
1603static inline int get_undo_list(struct sem_undo_list **undo_listp)
1604{
1605        struct sem_undo_list *undo_list;
1606
1607        undo_list = current->sysvsem.undo_list;
1608        if (!undo_list) {
1609                undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1610                if (undo_list == NULL)
1611                        return -ENOMEM;
1612                spin_lock_init(&undo_list->lock);
1613                atomic_set(&undo_list->refcnt, 1);
1614                INIT_LIST_HEAD(&undo_list->list_proc);
1615
1616                current->sysvsem.undo_list = undo_list;
1617        }
1618        *undo_listp = undo_list;
1619        return 0;
1620}
1621
1622static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1623{
1624        struct sem_undo *un;
1625
1626        list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1627                if (un->semid == semid)
1628                        return un;
1629        }
1630        return NULL;
1631}
1632
1633static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1634{
1635        struct sem_undo *un;
1636
1637        assert_spin_locked(&ulp->lock);
1638
1639        un = __lookup_undo(ulp, semid);
1640        if (un) {
1641                list_del_rcu(&un->list_proc);
1642                list_add_rcu(&un->list_proc, &ulp->list_proc);
1643        }
1644        return un;
1645}
1646
1647/**
1648 * find_alloc_undo - Lookup (and if not present create) undo array
1649 * @ns: namespace
1650 * @semid: semaphore array id
1651 *
1652 * The function looks up (and if not present creates) the undo structure.
1653 * The size of the undo structure depends on the size of the semaphore
1654 * array, thus the alloc path is not that straightforward.
1655 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1656 * performs a rcu_read_lock().
1657 */
1658static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1659{
1660        struct sem_array *sma;
1661        struct sem_undo_list *ulp;
1662        struct sem_undo *un, *new;
1663        int nsems, error;
1664
1665        error = get_undo_list(&ulp);
1666        if (error)
1667                return ERR_PTR(error);
1668
1669        rcu_read_lock();
1670        spin_lock(&ulp->lock);
1671        un = lookup_undo(ulp, semid);
1672        spin_unlock(&ulp->lock);
1673        if (likely(un!=NULL))
1674                goto out;
1675
1676        /* no undo structure around - allocate one. */
1677        /* step 1: figure out the size of the semaphore array */
1678        sma = sem_obtain_object_check(ns, semid);
1679        if (IS_ERR(sma)) {
1680                rcu_read_unlock();
1681                return ERR_CAST(sma);
1682        }
1683
1684        nsems = sma->sem_nsems;
1685        if (!ipc_rcu_getref(sma)) {
1686                rcu_read_unlock();
1687                un = ERR_PTR(-EIDRM);
1688                goto out;
1689        }
1690        rcu_read_unlock();
1691
1692        /* step 2: allocate new undo structure */
1693        new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1694        if (!new) {
1695                ipc_rcu_putref(sma, ipc_rcu_free);
1696                return ERR_PTR(-ENOMEM);
1697        }
1698
1699        /* step 3: Acquire the lock on semaphore array */
1700        rcu_read_lock();
1701        sem_lock_and_putref(sma);
1702        if (sma->sem_perm.deleted) {
1703                sem_unlock(sma, -1);
1704                rcu_read_unlock();
1705                kfree(new);
1706                un = ERR_PTR(-EIDRM);
1707                goto out;
1708        }
1709        spin_lock(&ulp->lock);
1710
1711        /*
1712         * step 4: check for races: did someone else allocate the undo struct?
1713         */
1714        un = lookup_undo(ulp, semid);
1715        if (un) {
1716                kfree(new);
1717                goto success;
1718        }
1719        /* step 5: initialize & link new undo structure */
1720        new->semadj = (short *) &new[1];
1721        new->ulp = ulp;
1722        new->semid = semid;
1723        assert_spin_locked(&ulp->lock);
1724        list_add_rcu(&new->list_proc, &ulp->list_proc);
1725        ipc_assert_locked_object(&sma->sem_perm);
1726        list_add(&new->list_id, &sma->list_id);
1727        un = new;
1728
1729success:
1730        spin_unlock(&ulp->lock);
1731        sem_unlock(sma, -1);
1732out:
1733        return un;
1734}
1735
1736
1737/**
1738 * get_queue_result - Retrieve the result code from sem_queue
1739 * @q: Pointer to queue structure
1740 *
1741 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1742 * q->status, then we must loop until the value is replaced with the final
1743 * value: This may happen if a task is woken up by an unrelated event (e.g.
1744 * signal) and in parallel the task is woken up by another task because it got
1745 * the requested semaphores.
1746 *
1747 * The function can be called with or without holding the semaphore spinlock.
1748 */
1749static int get_queue_result(struct sem_queue *q)
1750{
1751        int error;
1752
1753        error = q->status;
1754        while (unlikely(error == IN_WAKEUP)) {
1755                cpu_relax();
1756                error = q->status;
1757        }
1758
1759        return error;
1760}
1761
1762SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1763                unsigned, nsops, const struct timespec __user *, timeout)
1764{
1765        int error = -EINVAL;
1766        struct sem_array *sma;
1767        struct sembuf fast_sops[SEMOPM_FAST];
1768        struct sembuf* sops = fast_sops, *sop;
1769        struct sem_undo *un;
1770        int undos = 0, alter = 0, max, locknum;
1771        struct sem_queue queue;
1772        unsigned long jiffies_left = 0;
1773        struct ipc_namespace *ns;
1774        struct list_head tasks;
1775
1776        ns = current->nsproxy->ipc_ns;
1777
1778        if (nsops < 1 || semid < 0)
1779                return -EINVAL;
1780        if (nsops > ns->sc_semopm)
1781                return -E2BIG;
1782        if(nsops > SEMOPM_FAST) {
1783                sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1784                if(sops==NULL)
1785                        return -ENOMEM;
1786        }
1787        if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1788                error=-EFAULT;
1789                goto out_free;
1790        }
1791        if (timeout) {
1792                struct timespec _timeout;
1793                if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1794                        error = -EFAULT;
1795                        goto out_free;
1796                }
1797                if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1798                        _timeout.tv_nsec >= 1000000000L) {
1799                        error = -EINVAL;
1800                        goto out_free;
1801                }
1802                jiffies_left = timespec_to_jiffies(&_timeout);
1803        }
1804        max = 0;
1805        for (sop = sops; sop < sops + nsops; sop++) {
1806                if (sop->sem_num >= max)
1807                        max = sop->sem_num;
1808                if (sop->sem_flg & SEM_UNDO)
1809                        undos = 1;
1810                if (sop->sem_op != 0)
1811                        alter = 1;
1812        }
1813
1814        INIT_LIST_HEAD(&tasks);
1815
1816        if (undos) {
1817                /* On success, find_alloc_undo takes the rcu_read_lock */
1818                un = find_alloc_undo(ns, semid);
1819                if (IS_ERR(un)) {
1820                        error = PTR_ERR(un);
1821                        goto out_free;
1822                }
1823        } else {
1824                un = NULL;
1825                rcu_read_lock();
1826        }
1827
1828        sma = sem_obtain_object_check(ns, semid);
1829        if (IS_ERR(sma)) {
1830                rcu_read_unlock();
1831                error = PTR_ERR(sma);
1832                goto out_free;
1833        }
1834
1835        error = -EFBIG;
1836        if (max >= sma->sem_nsems)
1837                goto out_rcu_wakeup;
1838
1839        error = -EACCES;
1840        if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1841                goto out_rcu_wakeup;
1842
1843        error = security_sem_semop(sma, sops, nsops, alter);
1844        if (error)
1845                goto out_rcu_wakeup;
1846
1847        error = -EIDRM;
1848        locknum = sem_lock(sma, sops, nsops);
1849        if (sma->sem_perm.deleted)
1850                goto out_unlock_free;
1851        /*
1852         * semid identifiers are not unique - find_alloc_undo may have
1853         * allocated an undo structure, it was invalidated by an RMID
1854         * and now a new array with received the same id. Check and fail.
1855         * This case can be detected checking un->semid. The existence of
1856         * "un" itself is guaranteed by rcu.
1857         */
1858        if (un && un->semid == -1)
1859                goto out_unlock_free;
1860
1861        error = perform_atomic_semop(sma, sops, nsops, un,
1862                                        task_tgid_vnr(current));
1863        if (error == 0) {
1864                /* If the operation was successful, then do
1865                 * the required updates.
1866                 */
1867                if (alter)
1868                        do_smart_update(sma, sops, nsops, 1, &tasks);
1869                else
1870                        set_semotime(sma, sops);
1871        }
1872        if (error <= 0)
1873                goto out_unlock_free;
1874
1875        /* We need to sleep on this operation, so we put the current
1876         * task into the pending queue and go to sleep.
1877         */
1878                
1879        queue.sops = sops;
1880        queue.nsops = nsops;
1881        queue.undo = un;
1882        queue.pid = task_tgid_vnr(current);
1883        queue.alter = alter;
1884
1885        if (nsops == 1) {
1886                struct sem *curr;
1887                curr = &sma->sem_base[sops->sem_num];
1888
1889                if (alter) {
1890                        if (sma->complex_count) {
1891                                list_add_tail(&queue.list,
1892                                                &sma->pending_alter);
1893                        } else {
1894
1895                                list_add_tail(&queue.list,
1896                                                &curr->pending_alter);
1897                        }
1898                } else {
1899                        list_add_tail(&queue.list, &curr->pending_const);
1900                }
1901        } else {
1902                if (!sma->complex_count)
1903                        merge_queues(sma);
1904
1905                if (alter)
1906                        list_add_tail(&queue.list, &sma->pending_alter);
1907                else
1908                        list_add_tail(&queue.list, &sma->pending_const);
1909
1910                sma->complex_count++;
1911        }
1912
1913        queue.status = -EINTR;
1914        queue.sleeper = current;
1915
1916sleep_again:
1917        current->state = TASK_INTERRUPTIBLE;
1918        sem_unlock(sma, locknum);
1919        rcu_read_unlock();
1920
1921        if (timeout)
1922                jiffies_left = schedule_timeout(jiffies_left);
1923        else
1924                schedule();
1925
1926        error = get_queue_result(&queue);
1927
1928        if (error != -EINTR) {
1929                /* fast path: update_queue already obtained all requested
1930                 * resources.
1931                 * Perform a smp_mb(): User space could assume that semop()
1932                 * is a memory barrier: Without the mb(), the cpu could
1933                 * speculatively read in user space stale data that was
1934                 * overwritten by the previous owner of the semaphore.
1935                 */
1936                smp_mb();
1937
1938                goto out_free;
1939        }
1940
1941        rcu_read_lock();
1942        sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1943
1944        /*
1945         * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1946         */
1947        error = get_queue_result(&queue);
1948
1949        /*
1950         * Array removed? If yes, leave without sem_unlock().
1951         */
1952        if (IS_ERR(sma)) {
1953                rcu_read_unlock();
1954                goto out_free;
1955        }
1956
1957
1958        /*
1959         * If queue.status != -EINTR we are woken up by another process.
1960         * Leave without unlink_queue(), but with sem_unlock().
1961         */
1962
1963        if (error != -EINTR) {
1964                goto out_unlock_free;
1965        }
1966
1967        /*
1968         * If an interrupt occurred we have to clean up the queue
1969         */
1970        if (timeout && jiffies_left == 0)
1971                error = -EAGAIN;
1972
1973        /*
1974         * If the wakeup was spurious, just retry
1975         */
1976        if (error == -EINTR && !signal_pending(current))
1977                goto sleep_again;
1978
1979        unlink_queue(sma, &queue);
1980
1981out_unlock_free:
1982        sem_unlock(sma, locknum);
1983out_rcu_wakeup:
1984        rcu_read_unlock();
1985        wake_up_sem_queue_do(&tasks);
1986out_free:
1987        if(sops != fast_sops)
1988                kfree(sops);
1989        return error;
1990}
1991
1992SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1993                unsigned, nsops)
1994{
1995        return sys_semtimedop(semid, tsops, nsops, NULL);
1996}
1997
1998/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1999 * parent and child tasks.
2000 */
2001
2002int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2003{
2004        struct sem_undo_list *undo_list;
2005        int error;
2006
2007        if (clone_flags & CLONE_SYSVSEM) {
2008                error = get_undo_list(&undo_list);
2009                if (error)
2010                        return error;
2011                atomic_inc(&undo_list->refcnt);
2012                tsk->sysvsem.undo_list = undo_list;
2013        } else 
2014                tsk->sysvsem.undo_list = NULL;
2015
2016        return 0;
2017}
2018
2019/*
2020 * add semadj values to semaphores, free undo structures.
2021 * undo structures are not freed when semaphore arrays are destroyed
2022 * so some of them may be out of date.
2023 * IMPLEMENTATION NOTE: There is some confusion over whether the
2024 * set of adjustments that needs to be done should be done in an atomic
2025 * manner or not. That is, if we are attempting to decrement the semval
2026 * should we queue up and wait until we can do so legally?
2027 * The original implementation attempted to do this (queue and wait).
2028 * The current implementation does not do so. The POSIX standard
2029 * and SVID should be consulted to determine what behavior is mandated.
2030 */
2031void exit_sem(struct task_struct *tsk)
2032{
2033        struct sem_undo_list *ulp;
2034
2035        ulp = tsk->sysvsem.undo_list;
2036        if (!ulp)
2037                return;
2038        tsk->sysvsem.undo_list = NULL;
2039
2040        if (!atomic_dec_and_test(&ulp->refcnt))
2041                return;
2042
2043        for (;;) {
2044                struct sem_array *sma;
2045                struct sem_undo *un;
2046                struct list_head tasks;
2047                int semid, i;
2048
2049                rcu_read_lock();
2050                un = list_entry_rcu(ulp->list_proc.next,
2051                                    struct sem_undo, list_proc);
2052                if (&un->list_proc == &ulp->list_proc)
2053                        semid = -1;
2054                 else
2055                        semid = un->semid;
2056
2057                if (semid == -1) {
2058                        rcu_read_unlock();
2059                        break;
2060                }
2061
2062                sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
2063                /* exit_sem raced with IPC_RMID, nothing to do */
2064                if (IS_ERR(sma)) {
2065                        rcu_read_unlock();
2066                        continue;
2067                }
2068
2069                sem_lock(sma, NULL, -1);
2070                /* exit_sem raced with IPC_RMID, nothing to do */
2071                if (sma->sem_perm.deleted) {
2072                        sem_unlock(sma, -1);
2073                        rcu_read_unlock();
2074                        continue;
2075                }
2076                un = __lookup_undo(ulp, semid);
2077                if (un == NULL) {
2078                        /* exit_sem raced with IPC_RMID+semget() that created
2079                         * exactly the same semid. Nothing to do.
2080                         */
2081                        sem_unlock(sma, -1);
2082                        rcu_read_unlock();
2083                        continue;
2084                }
2085
2086                /* remove un from the linked lists */
2087                ipc_assert_locked_object(&sma->sem_perm);
2088                list_del(&un->list_id);
2089
2090                spin_lock(&ulp->lock);
2091                list_del_rcu(&un->list_proc);
2092                spin_unlock(&ulp->lock);
2093
2094                /* perform adjustments registered in un */
2095                for (i = 0; i < sma->sem_nsems; i++) {
2096                        struct sem * semaphore = &sma->sem_base[i];
2097                        if (un->semadj[i]) {
2098                                semaphore->semval += un->semadj[i];
2099                                /*
2100                                 * Range checks of the new semaphore value,
2101                                 * not defined by sus:
2102                                 * - Some unices ignore the undo entirely
2103                                 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2104                                 * - some cap the value (e.g. FreeBSD caps
2105                                 *   at 0, but doesn't enforce SEMVMX)
2106                                 *
2107                                 * Linux caps the semaphore value, both at 0
2108                                 * and at SEMVMX.
2109                                 *
2110                                 *      Manfred <manfred@colorfullife.com>
2111                                 */
2112                                if (semaphore->semval < 0)
2113                                        semaphore->semval = 0;
2114                                if (semaphore->semval > SEMVMX)
2115                                        semaphore->semval = SEMVMX;
2116                                semaphore->sempid = task_tgid_vnr(current);
2117                        }
2118                }
2119                /* maybe some queued-up processes were waiting for this */
2120                INIT_LIST_HEAD(&tasks);
2121                do_smart_update(sma, NULL, 0, 1, &tasks);
2122                sem_unlock(sma, -1);
2123                rcu_read_unlock();
2124                wake_up_sem_queue_do(&tasks);
2125
2126                kfree_rcu(un, rcu);
2127        }
2128        kfree(ulp);
2129}
2130
2131#ifdef CONFIG_PROC_FS
2132static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2133{
2134        struct user_namespace *user_ns = seq_user_ns(s);
2135        struct sem_array *sma = it;
2136        time_t sem_otime;
2137
2138        /*
2139         * The proc interface isn't aware of sem_lock(), it calls
2140         * ipc_lock_object() directly (in sysvipc_find_ipc).
2141         * In order to stay compatible with sem_lock(), we must wait until
2142         * all simple semop() calls have left their critical regions.
2143         */
2144        sem_wait_array(sma);
2145
2146        sem_otime = get_semotime(sma);
2147
2148        return seq_printf(s,
2149                          "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2150                          sma->sem_perm.key,
2151                          sma->sem_perm.id,
2152                          sma->sem_perm.mode,
2153                          sma->sem_nsems,
2154                          from_kuid_munged(user_ns, sma->sem_perm.uid),
2155                          from_kgid_munged(user_ns, sma->sem_perm.gid),
2156                          from_kuid_munged(user_ns, sma->sem_perm.cuid),
2157                          from_kgid_munged(user_ns, sma->sem_perm.cgid),
2158                          sem_otime,
2159                          sma->sem_ctime);
2160}
2161#endif
2162
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