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/mman.h>
  34 #include <sys/queue.h>
  35 #include <sys/stat.h>
  36 #include <sys/types.h>
  37 #include <errno.h>
  38 #include <fcntl.h>
  39 #include <limits.h>
  40 #include <pthread.h>
  41 #include <semaphore.h>
  42 #include <stdarg.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <time.h>
  46 #include <unistd.h>
  47 #ifdef _PTHREADS_DEBUGGING
  48 #include <stdio.h>
  49 #endif
  50 #include "un-namespace.h"
  51
  52 #include "thr_private.h"
  53
  54 #define cpu_ccfence()        __asm __volatile("" : : : "memory")
  55
  56 #define container_of(ptr, type, member)                         \
  57 ({                                                              \
  58         __typeof(((type *)0)->member) *_p = (ptr);              \
  59         (type *)((char *)_p - offsetof(type, member));          \
  60 })
  61
  62 /*
  63  * Semaphore definitions.
  64  */
  65 struct sem {
  66         volatile umtx_t         count;
  67         u_int32_t               magic;
  68         int                     semid;
  69         int                     unused; /* pad */
  70 } __cachealign;
  71
  72 #define SEM_MAGIC       ((u_int32_t) 0x09fa4012)
  73
  74 static char const *sem_prefix = "/var/run/sem";
  75
  76
  77 /*
  78  * POSIX requires that two successive calls to sem_open return
  79  * the same address if no call to unlink nor close have been
  80  * done in the middle. For that, we keep a list of open semaphore
  81  * and search for an existing one before remapping a semaphore.
  82  * We have to keep the fd open to check for races.
  83  *
  84  * Example :
  85  * sem_open("/test", O_CREAT | O_EXCL...) -> fork() ->
  86  * parent :
  87  *   sem_unlink("/test") -> sem_open("/test", O_CREAT | O_EXCl ...)
  88  * child :
  89  *   sem_open("/test", 0).
  90  * We need to check that the cached mapping is the one of the most up
  91  * to date file linked at this name, or child process will reopen the
  92  * *old* version of the semaphore, which is wrong.
  93  *
  94  * fstat and nlink check is used to test for this race.
  95  */
  96
  97 struct sem_info {
  98         int open_count;
  99         ino_t inode;
 100         dev_t dev;
 101         int fd;
 102         sem_t sem;
 103         LIST_ENTRY(sem_info) next;
 104 };
 105
 106 static pthread_mutex_t sem_lock;
 107 static LIST_HEAD(,sem_info) sem_list = LIST_HEAD_INITIALIZER(sem_list);
 108
 109 #ifdef _PTHREADS_DEBUGGING
 110
 111 static
 112 void
 113 sem_log(const char *ctl, ...)
 114 {
 115         char buf[256];
 116         va_list va;
 117         size_t len;
 118
 119         va_start(va, ctl);
 120         len = vsnprintf(buf, sizeof(buf), ctl, va);
 121         va_end(va);
 122         _thr_log(buf, len);
 123 }
 124
 125 #else
 126
 127 static __inline
 128 void
 129 sem_log(const char *ctl __unused, ...)
 130 {
 131 }
 132
 133 #endif
 134
 135 #define SEMID_LWP       0
 136 #define SEMID_FORK      1
 137 #define SEMID_NAMED     2
 138
 139 static void
 140 sem_prefork(void)
 141 {
 142         _pthread_mutex_lock(&sem_lock);
 143 }
 144
 145 static void
 146 sem_postfork(void)
 147 {
 148         _pthread_mutex_unlock(&sem_lock);
 149 }
 150
 151 static void
 152 sem_child_postfork(void)
 153 {
 154         _pthread_mutex_unlock(&sem_lock);
 155 }
 156
 157 void
 158 _thr_sem_init(void)
 159 {
 160         pthread_mutexattr_t ma;
 161
 162         _pthread_mutexattr_init(&ma);
 163         _pthread_mutexattr_settype(&ma,  PTHREAD_MUTEX_RECURSIVE);
 164         _pthread_mutex_init(&sem_lock, &ma);
 165         _pthread_mutexattr_destroy(&ma);
 166         _thr_atfork_kern(sem_prefork, sem_postfork, sem_child_postfork);
 167 }
 168
 169 static inline int
 170 sem_check_validity(sem_t *sem)
 171 {
 172
 173         if ((sem != NULL) && (*sem != NULL) && ((*sem)->magic == SEM_MAGIC)) {
 174                 return (0);
 175         } else {
 176                 errno = EINVAL;
 177                 return (-1);
 178         }
 179 }
 180
 181 static sem_t
 182 sem_alloc(unsigned int value, int pshared)
 183 {
 184         sem_t sem;
 185         int semid;
 186
 187         if (value > SEM_VALUE_MAX) {
 188                 errno = EINVAL;
 189                 return (NULL);
 190         }
 191         if (pshared) {
 192                 static __thread sem_t sem_base;
 193                 static __thread int sem_count;
 194
 195                 if (sem_base == NULL) {
 196                         sem_base = mmap(NULL, getpagesize(),
 197                                         PROT_READ | PROT_WRITE,
 198                                         MAP_ANON | MAP_SHARED,
 199                                         -1, 0);
 200                         sem_count = getpagesize() / sizeof(*sem);
 201                 }
 202                 sem = sem_base++;
 203                 if (--sem_count == 0)
 204                         sem_base = NULL;
 205                 semid = SEMID_FORK;
 206         } else {
 207                 sem = __malloc(sizeof(struct sem));
 208                 semid = SEMID_LWP;
 209         }
 210         if (sem == NULL) {
 211                 errno = ENOSPC;
 212                 return (NULL);
 213         }
 214         sem->magic = SEM_MAGIC;
 215         sem->count = (u_int32_t)value;
 216         sem->semid = semid;
 217
 218         sem_log("sem_alloc %p (%d)\n", sem, value);
 219
 220         return (sem);
 221 }
 222
 223 int
 224 _sem_init(sem_t *sem, int pshared, unsigned int value)
 225 {
 226         if (sem == NULL) {
 227                 errno = EINVAL;
 228                 return (-1);
 229         }
 230
 231         *sem = sem_alloc(value, pshared);
 232         if (*sem == NULL)
 233                 return (-1);
 234         return (0);
 235 }
 236
 237 int
 238 _sem_destroy(sem_t *sem)
 239 {
 240         if (sem_check_validity(sem) != 0) {
 241                 errno = EINVAL;
 242                 return (-1);
 243         }
 244
 245         (*sem)->magic = 0;
 246
 247         switch ((*sem)->semid) {
 248                 case SEMID_LWP:
 249                         __free(*sem);
 250                         break;
 251                 case SEMID_FORK:
 252                         /* memory is left intact */
 253                         break;
 254                 default:
 255                         errno = EINVAL;
 256                         return (-1);
 257         }
 258         return (0);
 259 }
 260
 261 int
 262 _sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
 263 {
 264         if (sem_check_validity(sem) != 0) {
 265                 errno = EINVAL;
 266                 return (-1);
 267         }
 268         *sval = (*sem)->count;
 269
 270         return (0);
 271 }
 272
 273 int
 274 _sem_trywait(sem_t *sem)
 275 {
 276         int val;
 277
 278         if (sem_check_validity(sem) != 0) {
 279                 errno = EINVAL;
 280                 return (-1);
 281         }
 282
 283         sem_log("sem_trywait %p %d\n", *sem, (*sem)->count);
 284         while ((val = (*sem)->count) > 0) {
 285                 cpu_ccfence();
 286                 if (atomic_cmpset_int(&(*sem)->count, val, val - 1)) {
 287                         sem_log("sem_trywait %p %d (success)\n", *sem, val - 1);
 288                         return (0);
 289                 }
 290         }
 291         errno = EAGAIN;
 292         sem_log("sem_trywait %p %d (failure)\n", *sem, val);
 293         return (-1);
 294 }
 295
 296 int
 297 _sem_wait(sem_t *sem)
 298 {
 299         pthread_t curthread;
 300         int val, oldcancel, retval;
 301
 302         if (sem_check_validity(sem) != 0) {
 303                 errno = EINVAL;
 304                 return (-1);
 305         }
 306
 307         curthread = tls_get_curthread();
 308         _pthread_testcancel();
 309
 310         sem_log("sem_wait %p %d (begin)\n", *sem, (*sem)->count);
 311
 312         do {
 313                 cpu_ccfence();
 314                 while ((val = (*sem)->count) > 0) {
 315                         cpu_ccfence();
 316                         if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1)) {
 317                                 sem_log("sem_wait %p %d (success)\n",
 318                                         *sem, val - 1);
 319                                 return (0);
 320                         }
 321                 }
 322                 oldcancel = _thr_cancel_enter(curthread);
 323                 sem_log("sem_wait %p %d (wait)\n", *sem, val);
 324                 retval = _thr_umtx_wait_intr(&(*sem)->count, 0);
 325                 sem_log("sem_wait %p %d (wait return %d)\n",
 326                         *sem, (*sem)->count, retval);
 327                 _thr_cancel_leave(curthread, oldcancel);
 328                 /* ignore retval */
 329         } while (retval != EINTR);
 330
 331         sem_log("sem_wait %p %d (error %d)\n", *sem, retval);
 332         errno = retval;
 333
 334         return (-1);
 335 }
 336
 337 int
 338 _sem_timedwait(sem_t * __restrict sem, const struct timespec * __restrict abstime)
 339 {
 340         struct timespec ts, ts2;
 341         pthread_t curthread;
 342         int val, oldcancel, retval;
 343
 344         if (sem_check_validity(sem) != 0)
 345                 return (-1);
 346
 347         curthread = tls_get_curthread();
 348         _pthread_testcancel();
 349         sem_log("sem_timedwait %p %d (begin)\n", *sem, (*sem)->count);
 350
 351         /*
 352          * The timeout argument is only supposed to
 353          * be checked if the thread would have blocked.
 354          */
 355         do {
 356                 while ((val = (*sem)->count) > 0) {
 357                         cpu_ccfence();
 358                         if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1)) {
 359                                 sem_log("sem_wait %p %d (success)\n",
 360                                         *sem, val - 1);
 361                                 return (0);
 362                         }
 363                 }
 364                 if (abstime == NULL ||
 365                     abstime->tv_nsec >= 1000000000 ||
 366                     abstime->tv_nsec < 0) {
 367                         sem_log("sem_wait %p %d (bad abstime)\n", *sem, val);
 368                         errno = EINVAL;
 369                         return (-1);
 370                 }
 371                 clock_gettime(CLOCK_REALTIME, &ts);
 372                 timespecsub(abstime, &ts, &ts2);
 373                 oldcancel = _thr_cancel_enter(curthread);
 374                 sem_log("sem_wait %p %d (wait)\n", *sem, val);
 375                 retval = _thr_umtx_wait(&(*sem)->count, 0, &ts2,
 376                                         CLOCK_REALTIME);
 377                 sem_log("sem_wait %p %d (wait return %d)\n",
 378                         *sem, (*sem)->count, retval);
 379                 _thr_cancel_leave(curthread, oldcancel);
 380         } while (retval != ETIMEDOUT && retval != EINTR);
 381
 382         sem_log("sem_wait %p %d (error %d)\n", *sem, retval);
 383         errno = retval;
 384
 385         return (-1);
 386 }
 387
 388 int
 389 _sem_post(sem_t *sem)
 390 {
 391         int val;
 392
 393         if (sem_check_validity(sem) != 0)
 394                 return (-1);
 395
 396         /*
 397          * sem_post() is required to be safe to call from within
 398          * signal handlers, these code should work as that.
 399          */
 400         val = atomic_fetchadd_int(&(*sem)->count, 1) + 1;
 401         sem_log("sem_post %p %d\n", *sem, val);
 402         _thr_umtx_wake(&(*sem)->count, 0);
 403
 404         return (0);
 405 }
 406
 407 static int
 408 get_path(const char *name, char *path, size_t len, char const **prefix)
 409 {
 410         size_t path_len;
 411
 412         *prefix = NULL;
 413
 414         if (name[0] == '/') {
 415                 *prefix = getenv("LIBTHREAD_SEM_PREFIX");
 416
 417                 if (*prefix == NULL)
 418                         *prefix = sem_prefix;
 419
 420                 path_len = strlcpy(path, *prefix, len);
 421
 422                 if (path_len > len) {
 423                         return (ENAMETOOLONG);
 424                 }
 425         }
 426
 427         path_len = strlcat(path, name, len);
 428
 429         if (path_len > len)
 430                 return (ENAMETOOLONG);
 431
 432         return (0);
 433 }
 434
 435
 436 static sem_t *
 437 sem_get_mapping(ino_t inode, dev_t dev)
 438 {
 439         struct sem_info *ni;
 440         struct stat sbuf;
 441
 442         LIST_FOREACH(ni, &sem_list, next) {
 443                 if (ni->inode == inode && ni->dev == dev) {
 444                         /* Check for races */
 445                         if(_fstat(ni->fd, &sbuf) == 0) {
 446                                 if (sbuf.st_nlink > 0) {
 447                                         ni->open_count++;
 448                                         return (&ni->sem);
 449                                 } else {
 450                                         ni->inode = 0;
 451                                         LIST_REMOVE(ni, next);
 452                                 }
 453                         }
 454                         return (SEM_FAILED);
 455
 456                 }
 457         }
 458
 459         return (SEM_FAILED);
 460 }
 461
 462
 463 static sem_t *
 464 sem_add_mapping(ino_t inode, dev_t dev, sem_t sem, int fd)
 465 {
 466         struct sem_info *ni;
 467
 468         ni = __malloc(sizeof(struct sem_info));
 469         if (ni == NULL) {
 470                 errno = ENOSPC;
 471                 return (SEM_FAILED);
 472         }
 473
 474         bzero(ni, sizeof(*ni));
 475         ni->open_count = 1;
 476         ni->sem = sem;
 477         ni->fd = fd;
 478         ni->inode = inode;
 479         ni->dev = dev;
 480
 481         LIST_INSERT_HEAD(&sem_list, ni, next);
 482
 483         return (&ni->sem);
 484 }
 485
 486 static int
 487 sem_close_mapping(sem_t *sem)
 488 {
 489         struct sem_info *ni;
 490
 491         if ((*sem)->semid != SEMID_NAMED)
 492                 return (EINVAL);
 493
 494         ni = container_of(sem, struct sem_info, sem);
 495
 496         if ( --ni->open_count > 0) {
 497                 return (0);
 498         } else {
 499                 if (ni->inode != 0) {
 500                         LIST_REMOVE(ni, next);
 501                 }
 502                 munmap(ni->sem, getpagesize());
 503                 __sys_close(ni->fd);
 504                 __free(ni);
 505                 return (0);
 506         }
 507 }
 508
 509 sem_t *
 510 _sem_open(const char *name, int oflag, ...)
 511 {
 512         char path[PATH_MAX];
 513         char tmppath[PATH_MAX];
 514         char const *prefix = NULL;
 515         size_t path_len;
 516         int error, fd, create;
 517         sem_t *sem;
 518         sem_t semtmp;
 519         va_list ap;
 520         mode_t mode;
 521         struct stat sbuf;
 522         unsigned int value = 0;
 523
 524         create = 0;
 525         error = 0;
 526         fd = -1;
 527         sem = SEM_FAILED;
 528
 529         /*
 530          * Bail out if invalid flags specified.
 531          */
 532         if (oflag & ~(O_CREAT|O_EXCL)) {
 533                 errno = EINVAL;
 534                 return (SEM_FAILED);
 535         }
 536
 537         oflag |= O_RDWR;
 538         oflag |= O_CLOEXEC;
 539
 540         if (name == NULL) {
 541                 errno = EINVAL;
 542                 return (SEM_FAILED);
 543         }
 544
 545         _pthread_mutex_lock(&sem_lock);
 546
 547         error = get_path(name, path, PATH_MAX, &prefix);
 548         if (error) {
 549                 errno = error;
 550                 goto error;
 551         }
 552
 553 retry:
 554         fd = __sys_open(path, O_RDWR | O_CLOEXEC);
 555
 556         if (fd > 0) {
 557
 558                 if ((oflag & O_EXCL) == O_EXCL) {
 559                         __sys_close(fd);
 560                         errno = EEXIST;
 561                         goto error;
 562                 }
 563
 564                 if (_fstat(fd, &sbuf) != 0) {
 565                         /* Bad things happened, like another thread closing our descriptor */
 566                         __sys_close(fd);
 567                         errno = EINVAL;
 568                         goto error;
 569                 }
 570
 571                 sem = sem_get_mapping(sbuf.st_ino, sbuf.st_dev);
 572
 573                 if (sem != SEM_FAILED) {
 574                         __sys_close(fd);
 575                         goto done;
 576                 }
 577
 578                 if ((sbuf.st_mode & S_IFREG) == 0) {
 579                         /* We only want regular files here */
 580                         __sys_close(fd);
 581                         errno = EINVAL;
 582                         goto error;
 583                 }
 584         } else if ((oflag & O_CREAT) && errno == ENOENT) {
 585
 586                 va_start(ap, oflag);
 587
 588                 mode = (mode_t) va_arg(ap, int);
 589                 value = (unsigned int) va_arg(ap, int);
 590
 591                 va_end(ap);
 592
 593                 if (value > SEM_VALUE_MAX) {
 594                         errno = EINVAL;
 595                         goto error;
 596                 }
 597
 598                 strlcpy(tmppath, prefix, sizeof(tmppath));
 599                 path_len = strlcat(tmppath, "/sem.XXXXXX", sizeof(tmppath));
 600
 601                 if (path_len > sizeof(tmppath)) {
 602                         errno = ENAMETOOLONG;
 603                         goto error;
 604                 }
 605
 606
 607                 fd = mkstemp(tmppath);
 608
 609                 if ( fd == -1 ) {
 610                         errno = EINVAL;
 611                         goto error;
 612                 }
 613
 614                 error = fchmod(fd, mode);
 615                 if ( error == -1 ) {
 616                         __sys_close(fd);
 617                         errno = EINVAL;
 618                         goto error;
 619                 }
 620
 621                 error = __sys_fcntl(fd, F_SETFD, FD_CLOEXEC);
 622                 if ( error == -1 ) {
 623                         __sys_close(fd);
 624                         errno = EINVAL;
 625                         goto error;
 626                 }
 627
 628                 create = 1;
 629         }
 630
 631         if (fd == -1) {
 632                 switch (errno) {
 633                         case ENOTDIR:
 634                         case EISDIR:
 635                         case EMLINK:
 636                         case ELOOP:
 637                                 errno = EINVAL;
 638                                 break;
 639                         case EDQUOT:
 640                         case EIO:
 641                                 errno = ENOSPC;
 642                                 break;
 643                         case EROFS:
 644                                 errno = EACCES;
 645                 }
 646                 goto error;
 647         }
 648
 649         semtmp = (sem_t) mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
 650                         MAP_NOSYNC | MAP_SHARED, fd, 0);
 651
 652         if (semtmp == MAP_FAILED) {
 653                 if (errno != EACCES && errno != EMFILE)
 654                         errno = ENOMEM;
 655
 656                 if (create)
 657                         _unlink(tmppath);
 658
 659                 __sys_close(fd);
 660                 goto error;
 661         }
 662
 663         if (create) {
 664                 ftruncate(fd, sizeof(struct sem));
 665                 semtmp->magic = SEM_MAGIC;
 666                 semtmp->count = (u_int32_t)value;
 667                 semtmp->semid = SEMID_NAMED;
 668
 669                 if (link(tmppath, path) != 0) {
 670                         munmap(semtmp, getpagesize());
 671                         __sys_close(fd);
 672                         _unlink(tmppath);
 673
 674                         if (errno == EEXIST && (oflag & O_EXCL) == 0) {
 675                                 goto retry;
 676                         }
 677
 678                         goto error;
 679                 }
 680                 _unlink(tmppath);
 681
 682                 if (_fstat(fd, &sbuf) != 0) {
 683                         /* Bad things happened, like another thread closing our descriptor */
 684                         munmap(semtmp, getpagesize());
 685                         __sys_close(fd);
 686                         errno = EINVAL;
 687                         goto error;
 688                 }
 689
 690         }
 691         sem = sem_add_mapping(sbuf.st_ino, sbuf.st_dev, semtmp, fd);
 692
 693 done:
 694         _pthread_mutex_unlock(&sem_lock);
 695         return (sem);
 696
 697 error:
 698         _pthread_mutex_unlock(&sem_lock);
 699         return (SEM_FAILED);
 700
 701 }
 702
 703 int
 704 _sem_close(sem_t *sem)
 705 {
 706         _pthread_mutex_lock(&sem_lock);
 707
 708         if (sem_check_validity(sem)) {
 709                 _pthread_mutex_unlock(&sem_lock);
 710                 errno = EINVAL;
 711                 return (-1);
 712         }
 713
 714         if (sem_close_mapping(sem)) {
 715                 _pthread_mutex_unlock(&sem_lock);
 716                 errno = EINVAL;
 717                 return (-1);
 718         }
 719         _pthread_mutex_unlock(&sem_lock);
 720
 721         return (0);
 722 }
 723
 724 int
 725 _sem_unlink(const char *name)
 726 {
 727         char path[PATH_MAX];
 728         const char *prefix;
 729         int error;
 730
 731         error = get_path(name, path, PATH_MAX, &prefix);
 732         if (error) {
 733                 errno = error;
 734                 return (-1);
 735         }
 736
 737         error = _unlink(path);
 738
 739         if(error) {
 740                 if (errno != ENAMETOOLONG && errno != ENOENT)
 741                         errno = EACCES;
 742
 743                 return (-1);
 744         }
 745
 746         return (0);
 747 }
 748
 749 __strong_reference(_sem_destroy, sem_destroy);
 750 __strong_reference(_sem_getvalue, sem_getvalue);
 751 __strong_reference(_sem_init, sem_init);
 752 __strong_reference(_sem_trywait, sem_trywait);
 753 __strong_reference(_sem_wait, sem_wait);
 754 __strong_reference(_sem_timedwait, sem_timedwait);
 755 __strong_reference(_sem_post, sem_post);
 756 __strong_reference(_sem_open, sem_open);
 757 __strong_reference(_sem_close, sem_close);
 758 __strong_reference(_sem_unlink, sem_unlink);