lib/libthread_xu/thread/thr_sem.c

   1 /*
   2  * Copyright (C) 2005 David Xu <davidxu@freebsd.org>.
   3  * Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice(s), this list of conditions and the following disclaimer as
  11  *    the first lines of this file unmodified other than the possible
  12  *    addition of one or more copyright notices.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice(s), this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  21  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
  22  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  23  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  24  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  25  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  26  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
  27  * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
  28  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include "namespace.h"
  32 #include <machine/tls.h>
  33 #include <sys/semaphore.h>
  34 #include <sys/mman.h>
  35 #include <sys/queue.h>
  36 #include <sys/stat.h>
  37 #include <sys/types.h>
  38 #include <errno.h>
  39 #include <fcntl.h>
  40 #include <limits.h>
  41 #include <pthread.h>
  42 #include <stdarg.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <time.h>
  46 #include <unistd.h>
  47 #include "un-namespace.h"
  48
  49 #include "thr_private.h"
  50
  51 #define container_of(ptr, type, member)                         \
  52 ({                                                              \
  53         __typeof(((type *)0)->member) *_p = (ptr);              \
  54         (type *)((char *)_p - offsetof(type, member));          \
  55 })
  56
  57 /*
  58  * Semaphore definitions.
  59  */
  60 struct sem {
  61         u_int32_t               magic;
  62         volatile umtx_t         count;
  63         int                     semid;
  64         int                     unused; /* pad */
  65 };
  66
  67 #define SEM_MAGIC       ((u_int32_t) 0x09fa4012)
  68
  69 static char const *sem_prefix = "/var/run/sem";
  70
  71
  72 /*
  73  * POSIX requires that two successive calls to sem_open return
  74  * the same address if no call to unlink nor close have been
  75  * done in the middle. For that, we keep a list of open semaphore
  76  * and search for an existing one before remapping a semaphore.
  77  * We have to keep the fd open to check for races.
  78  *
  79  * Example :
  80  * sem_open("/test", O_CREAT | O_EXCL...) -> fork() ->
  81  * parent :
  82  *   sem_unlink("/test") -> sem_open("/test", O_CREAT | O_EXCl ...)
  83  * child :
  84  *   sem_open("/test", 0).
  85  * We need to check that the cached mapping is the one of the most up
  86  * to date file linked at this name, or child process will reopen the
  87  * *old* version of the semaphore, which is wrong.
  88  *
  89  * fstat and nlink check is used to test for this race.
  90  */
  91
  92 struct sem_info {
  93         int open_count;
  94         ino_t inode;
  95         dev_t dev;
  96         int fd;
  97         sem_t sem;
  98         LIST_ENTRY(sem_info) next;
  99 };
 100
 101
 102
 103 static pthread_once_t once = PTHREAD_ONCE_INIT;
 104 static pthread_mutex_t sem_lock;
 105 static LIST_HEAD(,sem_info) sem_list = LIST_HEAD_INITIALIZER(sem_list);
 106
 107
 108 #define SEMID_LWP       0
 109 #define SEMID_FORK      1
 110 #define SEMID_NAMED     2
 111
 112 static void
 113 sem_prefork(void)
 114 {
 115         _pthread_mutex_lock(&sem_lock);
 116 }
 117
 118 static void
 119 sem_postfork(void)
 120 {
 121         _pthread_mutex_unlock(&sem_lock);
 122 }
 123
 124 static void
 125 sem_child_postfork(void)
 126 {
 127         _pthread_mutex_unlock(&sem_lock);
 128 }
 129
 130 static void
 131 sem_module_init(void)
 132 {
 133         pthread_mutexattr_t ma;
 134
 135         _pthread_mutexattr_init(&ma);
 136         _pthread_mutexattr_settype(&ma,  PTHREAD_MUTEX_RECURSIVE);
 137         _pthread_mutex_init(&sem_lock, &ma);
 138         _pthread_mutexattr_destroy(&ma);
 139         _pthread_atfork(sem_prefork, sem_postfork, sem_child_postfork);
 140 }
 141
 142 static inline int
 143 sem_check_validity(sem_t *sem)
 144 {
 145
 146         if ((sem != NULL) && (*sem != NULL) && ((*sem)->magic == SEM_MAGIC)) {
 147                 return (0);
 148         } else {
 149                 errno = EINVAL;
 150                 return (-1);
 151         }
 152 }
 153
 154 static sem_t
 155 sem_alloc(unsigned int value, int pshared)
 156 {
 157         sem_t sem;
 158         int semid;
 159
 160         if (value > SEM_VALUE_MAX) {
 161                 errno = EINVAL;
 162                 return (NULL);
 163         }
 164         if (pshared) {
 165                 static __thread sem_t sem_base;
 166                 static __thread int sem_count;
 167
 168                 if (sem_base == NULL) {
 169                         sem_base = mmap(NULL, getpagesize(),
 170                                         PROT_READ | PROT_WRITE,
 171                                         MAP_ANON | MAP_SHARED,
 172                                         -1, 0);
 173                         sem_count = getpagesize() / sizeof(*sem);
 174                 }
 175                 sem = sem_base++;
 176                 if (--sem_count == 0)
 177                         sem_base = NULL;
 178                 semid = SEMID_FORK;
 179         } else {
 180                 sem = malloc(sizeof(struct sem));
 181                 semid = SEMID_LWP;
 182         }
 183         if (sem == NULL) {
 184                 errno = ENOSPC;
 185                 return (NULL);
 186         }
 187         sem->magic = SEM_MAGIC;
 188         sem->count = (u_int32_t)value;
 189         sem->semid = semid;
 190         return (sem);
 191 }
 192
 193 int
 194 _sem_init(sem_t *sem, int pshared, unsigned int value)
 195 {
 196         if (sem == NULL) {
 197                 errno = EINVAL;
 198                 return (-1);
 199         }
 200
 201         *sem = sem_alloc(value, pshared);
 202         if (*sem == NULL)
 203                 return (-1);
 204         return (0);
 205 }
 206
 207 int
 208 _sem_destroy(sem_t *sem)
 209 {
 210         if (sem_check_validity(sem) != 0) {
 211                 errno = EINVAL;
 212                 return (-1);
 213         }
 214
 215         (*sem)->magic = 0;
 216
 217         switch ((*sem)->semid) {
 218                 case SEMID_LWP:
 219                         free(*sem);
 220                         break;
 221                 case SEMID_FORK:
 222                         /* memory is left intact */
 223                         break;
 224                 default:
 225                         errno = EINVAL;
 226                         return (-1);
 227         }
 228         return (0);
 229 }
 230
 231 int
 232 _sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
 233 {
 234         if (sem_check_validity(sem) != 0)
 235                 return (-1);
 236
 237         *sval = (*sem)->count;
 238         return (0);
 239 }
 240
 241 int
 242 _sem_trywait(sem_t *sem)
 243 {
 244         int val;
 245
 246         if (sem_check_validity(sem) != 0)
 247                 return (-1);
 248
 249         while ((val = (*sem)->count) > 0) {
 250                 if (atomic_cmpset_int(&(*sem)->count, val, val - 1))
 251                         return (0);
 252         }
 253         errno = EAGAIN;
 254         return (-1);
 255 }
 256
 257 int
 258 _sem_wait(sem_t *sem)
 259 {
 260         struct pthread *curthread;
 261         int val, oldcancel, retval;
 262
 263         if (sem_check_validity(sem) != 0)
 264                 return (-1);
 265
 266         curthread = tls_get_curthread();
 267         _pthread_testcancel();
 268         do {
 269                 while ((val = (*sem)->count) > 0) {
 270                         if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
 271                                 return (0);
 272                 }
 273                 oldcancel = _thr_cancel_enter(curthread);
 274                 retval = _thr_umtx_wait(&(*sem)->count, 0, NULL, 0);
 275                 _thr_cancel_leave(curthread, oldcancel);
 276         } while (retval == 0);
 277         errno = retval;
 278         return (-1);
 279 }
 280
 281 int
 282 _sem_timedwait(sem_t * __restrict sem, const struct timespec * __restrict abstime)
 283 {
 284         struct timespec ts, ts2;
 285         struct pthread *curthread;
 286         int val, oldcancel, retval;
 287
 288         if (sem_check_validity(sem) != 0)
 289                 return (-1);
 290
 291         curthread = tls_get_curthread();
 292
 293         /*
 294          * The timeout argument is only supposed to
 295          * be checked if the thread would have blocked.
 296          */
 297         _pthread_testcancel();
 298         do {
 299                 while ((val = (*sem)->count) > 0) {
 300                         if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
 301                                 return (0);
 302                 }
 303                 if (abstime == NULL ||
 304                                 abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
 305                         errno = EINVAL;
 306                         return (-1);
 307                 }
 308                 clock_gettime(CLOCK_REALTIME, &ts);
 309                 TIMESPEC_SUB(&ts2, abstime, &ts);
 310                 oldcancel = _thr_cancel_enter(curthread);
 311                 retval = _thr_umtx_wait(&(*sem)->count, 0, &ts2,
 312                                 CLOCK_REALTIME);
 313                 _thr_cancel_leave(curthread, oldcancel);
 314         } while (retval == 0);
 315         errno = retval;
 316         return (-1);
 317 }
 318
 319 int
 320 _sem_post(sem_t *sem)
 321 {
 322         int val;
 323
 324         if (sem_check_validity(sem) != 0)
 325                 return (-1);
 326
 327         /*
 328          * sem_post() is required to be safe to call from within
 329          * signal handlers, these code should work as that.
 330          */
 331         do {
 332                 val = (*sem)->count;
 333         } while (!atomic_cmpset_acq_int(&(*sem)->count, val, val + 1));
 334         _thr_umtx_wake(&(*sem)->count, val + 1);
 335         return (0);
 336 }
 337
 338 static int
 339 get_path(const char *name, char *path, size_t len, char const **prefix)
 340 {
 341         size_t path_len;
 342
 343         *prefix = NULL;
 344
 345         if (name[0] == '/') {
 346                 *prefix = getenv("LIBTHREAD_SEM_PREFIX");
 347
 348                 if (*prefix == NULL)
 349                         *prefix = sem_prefix;
 350
 351                 path_len = strlcpy(path, *prefix, len);
 352
 353                 if (path_len > len) {
 354                         return (ENAMETOOLONG);
 355                 }
 356         }
 357
 358         path_len = strlcat(path, name, len);
 359
 360         if (path_len > len)
 361                 return (ENAMETOOLONG);
 362
 363         return (0);
 364 }
 365
 366
 367 static sem_t *
 368 sem_get_mapping(ino_t inode, dev_t dev)
 369 {
 370         struct sem_info *ni;
 371         struct stat sbuf;
 372
 373         LIST_FOREACH(ni, &sem_list, next) {
 374                 if (ni->inode == inode && ni->dev == dev) {
 375                         /* Check for races */
 376                         if(_fstat(ni->fd, &sbuf) == 0) {
 377                                 if (sbuf.st_nlink > 0) {
 378                                         ni->open_count++;
 379                                         return (&ni->sem);
 380                                 } else {
 381                                         ni->inode = 0;
 382                                         LIST_REMOVE(ni, next);
 383                                 }
 384                         }
 385                         return (SEM_FAILED);
 386
 387                 }
 388         }
 389
 390         return (SEM_FAILED);
 391 }
 392
 393
 394 static sem_t *
 395 sem_add_mapping(ino_t inode, dev_t dev, sem_t sem, int fd)
 396 {
 397         struct sem_info *ni;
 398
 399         ni = malloc(sizeof(struct sem_info));
 400         if (ni == NULL) {
 401                 errno = ENOSPC;
 402                 return (SEM_FAILED);
 403         }
 404
 405         bzero(ni, sizeof(*ni));
 406         ni->open_count = 1;
 407         ni->sem = sem;
 408         ni->fd = fd;
 409         ni->inode = inode;
 410         ni->dev = dev;
 411
 412         LIST_INSERT_HEAD(&sem_list, ni, next);
 413
 414         return (&ni->sem);
 415 }
 416
 417 static int
 418 sem_close_mapping(sem_t *sem)
 419 {
 420         struct sem_info *ni;
 421
 422         if ((*sem)->semid != SEMID_NAMED)
 423                 return (EINVAL);
 424
 425         ni = container_of(sem, struct sem_info, sem);
 426
 427         if ( --ni->open_count > 0) {
 428                 return (0);
 429         } else {
 430                 if (ni->inode != 0) {
 431                         LIST_REMOVE(ni, next);
 432                 }
 433                 munmap(ni->sem, getpagesize());
 434                 __sys_close(ni->fd);
 435                 free(ni);
 436                 return (0);
 437         }
 438 }
 439
 440 sem_t *
 441 _sem_open(const char *name, int oflag, ...)
 442 {
 443         char path[PATH_MAX];
 444         char tmppath[PATH_MAX];
 445         char const *prefix = NULL;
 446         size_t path_len;
 447         int error, fd, create;
 448         sem_t *sem;
 449         sem_t semtmp;
 450         va_list ap;
 451         mode_t mode;
 452         struct stat sbuf;
 453         unsigned int value = 0;
 454
 455         create = 0;
 456         error = 0;
 457         fd = -1;
 458         sem = SEM_FAILED;
 459
 460         /*
 461          * Bail out if invalid flags specified.
 462          */
 463         if (oflag & ~(O_CREAT|O_EXCL)) {
 464                 errno = EINVAL;
 465                 return (SEM_FAILED);
 466         }
 467
 468         oflag |= O_RDWR;
 469         oflag |= O_CLOEXEC;
 470
 471         if (name == NULL) {
 472                 errno = EINVAL;
 473                 return (SEM_FAILED);
 474         }
 475
 476         _pthread_once(&once, sem_module_init);
 477
 478         _pthread_mutex_lock(&sem_lock);
 479
 480         error = get_path(name, path, PATH_MAX, &prefix);
 481         if (error) {
 482                 errno = error;
 483                 goto error;
 484         }
 485
 486 retry:
 487         fd = __sys_open(path, O_RDWR | O_CLOEXEC);
 488
 489         if (fd > 0) {
 490
 491                 if ((oflag & O_EXCL) == O_EXCL) {
 492                         __sys_close(fd);
 493                         errno = EEXIST;
 494                         goto error;
 495                 }
 496
 497                 if (_fstat(fd, &sbuf) != 0) {
 498                         /* Bad things happened, like another thread closing our descriptor */
 499                         __sys_close(fd);
 500                         errno = EINVAL;
 501                         goto error;
 502                 }
 503
 504                 sem = sem_get_mapping(sbuf.st_ino, sbuf.st_dev);
 505
 506                 if (sem != SEM_FAILED) {
 507                         __sys_close(fd);
 508                         goto done;
 509                 }
 510
 511                 if ((sbuf.st_mode & S_IFREG) == 0) {
 512                         /* We only want regular files here */
 513                         __sys_close(fd);
 514                         errno = EINVAL;
 515                         goto error;
 516                 }
 517         } else if ((oflag & O_CREAT) && errno == ENOENT) {
 518
 519                 va_start(ap, oflag);
 520
 521                 mode = (mode_t) va_arg(ap, int);
 522                 value = (unsigned int) va_arg(ap, int);
 523
 524                 va_end(ap);
 525
 526                 if (value > SEM_VALUE_MAX) {
 527                         errno = EINVAL;
 528                         goto error;
 529                 }
 530
 531                 strlcpy(tmppath, prefix, sizeof(tmppath));
 532                 path_len = strlcat(tmppath, "/sem.XXXXXX", sizeof(tmppath));
 533
 534                 if (path_len > sizeof(tmppath)) {
 535                         errno = ENAMETOOLONG;
 536                         goto error;
 537                 }
 538
 539
 540                 fd = mkstemp(tmppath);
 541
 542                 if ( fd == -1 ) {
 543                         errno = EINVAL;
 544                         goto error;
 545                 }
 546
 547                 error = fchmod(fd, mode);
 548                 if ( error == -1 ) {
 549                         __sys_close(fd);
 550                         errno = EINVAL;
 551                         goto error;
 552                 }
 553
 554                 error = __sys_fcntl(fd, F_SETFD, FD_CLOEXEC);
 555                 if ( error == -1 ) {
 556                         __sys_close(fd);
 557                         errno = EINVAL;
 558                         goto error;
 559                 }
 560
 561                 create = 1;
 562         }
 563
 564         if (fd == -1) {
 565                 switch (errno) {
 566                         case ENOTDIR:
 567                         case EISDIR:
 568                         case EMLINK:
 569                         case ELOOP:
 570                                 errno = EINVAL;
 571                                 break;
 572                         case EDQUOT:
 573                         case EIO:
 574                                 errno = ENOSPC;
 575                                 break;
 576                         case EROFS:
 577                                 errno = EACCES;
 578                 }
 579                 goto error;
 580         }
 581
 582         semtmp = (sem_t) mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
 583                         MAP_NOSYNC | MAP_SHARED, fd, 0);
 584
 585         if (semtmp == MAP_FAILED) {
 586                 if (errno != EACCES && errno != EMFILE)
 587                         errno = ENOMEM;
 588
 589                 if (create)
 590                         unlink(tmppath);
 591
 592                 __sys_close(fd);
 593                 goto error;
 594         }
 595
 596         if (create) {
 597                 ftruncate(fd, sizeof(struct sem));
 598                 semtmp->magic = SEM_MAGIC;
 599                 semtmp->count = (u_int32_t)value;
 600                 semtmp->semid = SEMID_NAMED;
 601
 602                 if (link(tmppath, path) != 0) {
 603                         munmap(semtmp, getpagesize());
 604                         __sys_close(fd);
 605                         unlink(tmppath);
 606
 607                         if (errno == EEXIST && (oflag & O_EXCL) == 0) {
 608                                 goto retry;
 609                         }
 610
 611                         goto error;
 612                 }
 613                 unlink(tmppath);
 614
 615                 if (_fstat(fd, &sbuf) != 0) {
 616                         /* Bad things happened, like another thread closing our descriptor */
 617                         munmap(semtmp, getpagesize());
 618                         __sys_close(fd);
 619                         errno = EINVAL;
 620                         goto error;
 621                 }
 622
 623         }
 624         sem = sem_add_mapping(sbuf.st_ino, sbuf.st_dev, semtmp, fd);
 625
 626 done:
 627         _pthread_mutex_unlock(&sem_lock);
 628         return (sem);
 629
 630 error:
 631         _pthread_mutex_unlock(&sem_lock);
 632         return (SEM_FAILED);
 633
 634 }
 635
 636 int
 637 _sem_close(sem_t *sem)
 638 {
 639         _pthread_once(&once, sem_module_init);
 640
 641         _pthread_mutex_lock(&sem_lock);
 642
 643         if (sem_check_validity(sem)) {
 644                 _pthread_mutex_unlock(&sem_lock);
 645                 errno = EINVAL;
 646                 return (-1);
 647         }
 648
 649         if (sem_close_mapping(sem)) {
 650                 _pthread_mutex_unlock(&sem_lock);
 651                 errno = EINVAL;
 652                 return (-1);
 653         }
 654         _pthread_mutex_unlock(&sem_lock);
 655
 656         return (0);
 657 }
 658
 659 int
 660 _sem_unlink(const char *name)
 661 {
 662         char path[PATH_MAX];
 663         const char *prefix;
 664         int error;
 665
 666         error = get_path(name, path, PATH_MAX, &prefix);
 667         if (error) {
 668                 errno = error;
 669                 return (-1);
 670         }
 671
 672         error = unlink(path);
 673
 674         if(error) {
 675                 if (errno != ENAMETOOLONG && errno != ENOENT)
 676                         errno = EACCES;
 677
 678                 return (-1);
 679         }
 680
 681         return (0);
 682 }
 683
 684 __strong_reference(_sem_destroy, sem_destroy);
 685 __strong_reference(_sem_getvalue, sem_getvalue);
 686 __strong_reference(_sem_init, sem_init);
 687 __strong_reference(_sem_trywait, sem_trywait);
 688 __strong_reference(_sem_wait, sem_wait);
 689 __strong_reference(_sem_timedwait, sem_timedwait);
 690 __strong_reference(_sem_post, sem_post);
 691 __strong_reference(_sem_open, sem_open);
 692 __strong_reference(_sem_close, sem_close);
 693 __strong_reference(_sem_unlink, sem_unlink);