nptl/pthread_mutex_timedlock.c

   1 /* Copyright (C) 2002-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <time.h>
  22 #include <sys/param.h>
  23 #include <sys/time.h>
  24 #include "pthreadP.h"
  25 #include <atomic.h>
  26 #include <lowlevellock.h>
  27 #include <not-cancel.h>
  28
  29 #include <stap-probe.h>
  30
  31 #ifndef lll_timedlock_elision
  32 #define lll_timedlock_elision(a,dummy,b,c) lll_timedlock(a, b, c)
  33 #endif
  34
  35 #ifndef lll_trylock_elision
  36 #define lll_trylock_elision(a,t) lll_trylock(a)
  37 #endif
  38
  39 #ifndef FORCE_ELISION
  40 #define FORCE_ELISION(m, s)
  41 #endif
  42
  43 int
  44 __pthread_mutex_timedlock (pthread_mutex_t *mutex,
  45                            const struct timespec *abstime)
  46 {
  47   int oldval;
  48   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  49   int result = 0;
  50
  51   LIBC_PROBE (mutex_timedlock_entry, 2, mutex, abstime);
  52
  53   /* We must not check ABSTIME here.  If the thread does not block
  54      abstime must not be checked for a valid value.  */
  55
  56   switch (__builtin_expect (PTHREAD_MUTEX_TYPE_ELISION (mutex),
  57                             PTHREAD_MUTEX_TIMED_NP))
  58     {
  59       /* Recursive mutex.  */
  60     case PTHREAD_MUTEX_RECURSIVE_NP|PTHREAD_MUTEX_ELISION_NP:
  61     case PTHREAD_MUTEX_RECURSIVE_NP:
  62       /* Check whether we already hold the mutex.  */
  63       if (mutex->__data.__owner == id)
  64         {
  65           /* Just bump the counter.  */
  66           if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
  67             /* Overflow of the counter.  */
  68             return EAGAIN;
  69
  70           ++mutex->__data.__count;
  71
  72           goto out;
  73         }
  74
  75       /* We have to get the mutex.  */
  76       result = lll_timedlock (mutex->__data.__lock, abstime,
  77                               PTHREAD_MUTEX_PSHARED (mutex));
  78
  79       if (result != 0)
  80         goto out;
  81
  82       /* Only locked once so far.  */
  83       mutex->__data.__count = 1;
  84       break;
  85
  86       /* Error checking mutex.  */
  87     case PTHREAD_MUTEX_ERRORCHECK_NP:
  88       /* Check whether we already hold the mutex.  */
  89       if (__glibc_unlikely (mutex->__data.__owner == id))
  90         return EDEADLK;
  91
  92       /* Don't do lock elision on an error checking mutex.  */
  93       goto simple;
  94
  95     case PTHREAD_MUTEX_TIMED_NP:
  96       FORCE_ELISION (mutex, goto elision);
  97     simple:
  98       /* Normal mutex.  */
  99       result = lll_timedlock (mutex->__data.__lock, abstime,
 100                               PTHREAD_MUTEX_PSHARED (mutex));
 101       break;
 102
 103     case PTHREAD_MUTEX_TIMED_ELISION_NP:
 104     elision: __attribute__((unused))
 105       /* Don't record ownership */
 106       return lll_timedlock_elision (mutex->__data.__lock,
 107                                     mutex->__data.__spins,
 108                                     abstime,
 109                                     PTHREAD_MUTEX_PSHARED (mutex));
 110
 111
 112     case PTHREAD_MUTEX_ADAPTIVE_NP:
 113       if (! __is_smp)
 114         goto simple;
 115
 116       if (lll_trylock (mutex->__data.__lock) != 0)
 117         {
 118           int cnt = 0;
 119           int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
 120                              mutex->__data.__spins * 2 + 10);
 121           do
 122             {
 123               if (cnt++ >= max_cnt)
 124                 {
 125                   result = lll_timedlock (mutex->__data.__lock, abstime,
 126                                           PTHREAD_MUTEX_PSHARED (mutex));
 127                   break;
 128                 }
 129               atomic_spin_nop ();
 130             }
 131           while (lll_trylock (mutex->__data.__lock) != 0);
 132
 133           mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 134         }
 135       break;
 136
 137     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
 138     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
 139     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
 140     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
 141       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 142                      &mutex->__data.__list.__next);
 143       /* We need to set op_pending before starting the operation.  Also
 144          see comments at ENQUEUE_MUTEX.  */
 145       __asm ("" ::: "memory");
 146
 147       oldval = mutex->__data.__lock;
 148       /* This is set to FUTEX_WAITERS iff we might have shared the
 149          FUTEX_WAITERS flag with other threads, and therefore need to keep it
 150          set to avoid lost wake-ups.  We have the same requirement in the
 151          simple mutex algorithm.  */
 152       unsigned int assume_other_futex_waiters = 0;
 153       while (1)
 154         {
 155           /* Try to acquire the lock through a CAS from 0 (not acquired) to
 156              our TID | assume_other_futex_waiters.  */
 157           if (__glibc_likely (oldval == 0))
 158             {
 159               oldval
 160                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 161                     id | assume_other_futex_waiters, 0);
 162               if (__glibc_likely (oldval == 0))
 163                 break;
 164             }
 165
 166           if ((oldval & FUTEX_OWNER_DIED) != 0)
 167             {
 168               /* The previous owner died.  Try locking the mutex.  */
 169               int newval = id | (oldval & FUTEX_WAITERS)
 170                   | assume_other_futex_waiters;
 171
 172               newval
 173                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 174                                                        newval, oldval);
 175               if (newval != oldval)
 176                 {
 177                   oldval = newval;
 178                   continue;
 179                 }
 180
 181               /* We got the mutex.  */
 182               mutex->__data.__count = 1;
 183               /* But it is inconsistent unless marked otherwise.  */
 184               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 185
 186               /* We must not enqueue the mutex before we have acquired it.
 187                  Also see comments at ENQUEUE_MUTEX.  */
 188               __asm ("" ::: "memory");
 189               ENQUEUE_MUTEX (mutex);
 190               /* We need to clear op_pending after we enqueue the mutex.  */
 191               __asm ("" ::: "memory");
 192               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 193
 194               /* Note that we deliberately exit here.  If we fall
 195                  through to the end of the function __nusers would be
 196                  incremented which is not correct because the old
 197                  owner has to be discounted.  */
 198               return EOWNERDEAD;
 199             }
 200
 201           /* Check whether we already hold the mutex.  */
 202           if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))
 203             {
 204               int kind = PTHREAD_MUTEX_TYPE (mutex);
 205               if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 206                 {
 207                   /* We do not need to ensure ordering wrt another memory
 208                      access.  Also see comments at ENQUEUE_MUTEX. */
 209                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 210                                  NULL);
 211                   return EDEADLK;
 212                 }
 213
 214               if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 215                 {
 216                   /* We do not need to ensure ordering wrt another memory
 217                      access.  */
 218                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 219                                  NULL);
 220
 221                   /* Just bump the counter.  */
 222                   if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
 223                     /* Overflow of the counter.  */
 224                     return EAGAIN;
 225
 226                   ++mutex->__data.__count;
 227
 228                   LIBC_PROBE (mutex_timedlock_acquired, 1, mutex);
 229
 230                   return 0;
 231                 }
 232             }
 233
 234           /* We are about to block; check whether the timeout is invalid.  */
 235           if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
 236             return EINVAL;
 237           /* Work around the fact that the kernel rejects negative timeout
 238              values despite them being valid.  */
 239           if (__glibc_unlikely (abstime->tv_sec < 0))
 240             return ETIMEDOUT;
 241 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 242      || !defined lll_futex_timed_wait_bitset)
 243           struct timeval tv;
 244           struct timespec rt;
 245
 246           /* Get the current time.  */
 247           (void) __gettimeofday (&tv, NULL);
 248
 249           /* Compute relative timeout.  */
 250           rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 251           rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 252           if (rt.tv_nsec < 0)
 253             {
 254               rt.tv_nsec += 1000000000;
 255               --rt.tv_sec;
 256             }
 257
 258           /* Already timed out?  */
 259           if (rt.tv_sec < 0)
 260             return ETIMEDOUT;
 261 #endif
 262
 263           /* We cannot acquire the mutex nor has its owner died.  Thus, try
 264              to block using futexes.  Set FUTEX_WAITERS if necessary so that
 265              other threads are aware that there are potentially threads
 266              blocked on the futex.  Restart if oldval changed in the
 267              meantime.  */
 268           if ((oldval & FUTEX_WAITERS) == 0)
 269             {
 270               if (atomic_compare_and_exchange_bool_acq (&mutex->__data.__lock,
 271                                                         oldval | FUTEX_WAITERS,
 272                                                         oldval)
 273                   != 0)
 274                 {
 275                   oldval = mutex->__data.__lock;
 276                   continue;
 277                 }
 278               oldval |= FUTEX_WAITERS;
 279             }
 280
 281           /* It is now possible that we share the FUTEX_WAITERS flag with
 282              another thread; therefore, update assume_other_futex_waiters so
 283              that we do not forget about this when handling other cases
 284              above and thus do not cause lost wake-ups.  */
 285           assume_other_futex_waiters |= FUTEX_WAITERS;
 286
 287           /* Block using the futex.  */
 288 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 289      || !defined lll_futex_timed_wait_bitset)
 290           lll_futex_timed wait (&mutex->__data.__lock, oldval,
 291                                 &rt, PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
 292 #else
 293           int err = lll_futex_timed_wait_bitset (&mutex->__data.__lock,
 294               oldval, abstime, FUTEX_CLOCK_REALTIME,
 295               PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
 296           /* The futex call timed out.  */
 297           if (err == -ETIMEDOUT)
 298             return -err;
 299 #endif
 300           /* Reload current lock value.  */
 301           oldval = mutex->__data.__lock;
 302         }
 303
 304       /* We have acquired the mutex; check if it is still consistent.  */
 305       if (__builtin_expect (mutex->__data.__owner
 306                             == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 307         {
 308           /* This mutex is now not recoverable.  */
 309           mutex->__data.__count = 0;
 310           int private = PTHREAD_ROBUST_MUTEX_PSHARED (mutex);
 311           lll_unlock (mutex->__data.__lock, private);
 312           /* FIXME This violates the mutex destruction requirements.  See
 313              __pthread_mutex_unlock_full.  */
 314           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 315           return ENOTRECOVERABLE;
 316         }
 317
 318       mutex->__data.__count = 1;
 319       /* We must not enqueue the mutex before we have acquired it.
 320          Also see comments at ENQUEUE_MUTEX.  */
 321       __asm ("" ::: "memory");
 322       ENQUEUE_MUTEX (mutex);
 323       /* We need to clear op_pending after we enqueue the mutex.  */
 324       __asm ("" ::: "memory");
 325       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 326       break;
 327
 328     /* The PI support requires the Linux futex system call.  If that's not
 329        available, pthread_mutex_init should never have allowed the type to
 330        be set.  So it will get the default case for an invalid type.  */
 331 #ifdef __NR_futex
 332     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 333     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 334     case PTHREAD_MUTEX_PI_NORMAL_NP:
 335     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 336     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 337     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 338     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 339     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 340       {
 341         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 342         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 343
 344         if (robust)
 345           {
 346             /* Note: robust PI futexes are signaled by setting bit 0.  */
 347             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 348                            (void *) (((uintptr_t) &mutex->__data.__list.__next)
 349                                      | 1));
 350             /* We need to set op_pending before starting the operation.  Also
 351                see comments at ENQUEUE_MUTEX.  */
 352             __asm ("" ::: "memory");
 353           }
 354
 355         oldval = mutex->__data.__lock;
 356
 357         /* Check whether we already hold the mutex.  */
 358         if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))
 359           {
 360             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 361               {
 362                 /* We do not need to ensure ordering wrt another memory
 363                    access.  */
 364                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 365                 return EDEADLK;
 366               }
 367
 368             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 369               {
 370                 /* We do not need to ensure ordering wrt another memory
 371                    access.  */
 372                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 373
 374                 /* Just bump the counter.  */
 375                 if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
 376                   /* Overflow of the counter.  */
 377                   return EAGAIN;
 378
 379                 ++mutex->__data.__count;
 380
 381                 LIBC_PROBE (mutex_timedlock_acquired, 1, mutex);
 382
 383                 return 0;
 384               }
 385           }
 386
 387         oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 388                                                       id, 0);
 389
 390         if (oldval != 0)
 391           {
 392             /* The mutex is locked.  The kernel will now take care of
 393                everything.  The timeout value must be a relative value.
 394                Convert it.  */
 395             int private = (robust
 396                            ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
 397                            : PTHREAD_MUTEX_PSHARED (mutex));
 398             INTERNAL_SYSCALL_DECL (__err);
 399
 400             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 401                                       __lll_private_flag (FUTEX_LOCK_PI,
 402                                                           private), 1,
 403                                       abstime);
 404             if (INTERNAL_SYSCALL_ERROR_P (e, __err))
 405               {
 406                 if (INTERNAL_SYSCALL_ERRNO (e, __err) == ETIMEDOUT)
 407                   return ETIMEDOUT;
 408
 409                 if (INTERNAL_SYSCALL_ERRNO (e, __err) == ESRCH
 410                     || INTERNAL_SYSCALL_ERRNO (e, __err) == EDEADLK)
 411                   {
 412                     assert (INTERNAL_SYSCALL_ERRNO (e, __err) != EDEADLK
 413                             || (kind != PTHREAD_MUTEX_ERRORCHECK_NP
 414                                 && kind != PTHREAD_MUTEX_RECURSIVE_NP));
 415                     /* ESRCH can happen only for non-robust PI mutexes where
 416                        the owner of the lock died.  */
 417                     assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH
 418                             || !robust);
 419
 420                     /* Delay the thread until the timeout is reached.
 421                        Then return ETIMEDOUT.  */
 422                     struct timespec reltime;
 423                     struct timespec now;
 424
 425                     INTERNAL_SYSCALL (clock_gettime, __err, 2, CLOCK_REALTIME,
 426                                       &now);
 427                     reltime.tv_sec = abstime->tv_sec - now.tv_sec;
 428                     reltime.tv_nsec = abstime->tv_nsec - now.tv_nsec;
 429                     if (reltime.tv_nsec < 0)
 430                       {
 431                         reltime.tv_nsec += 1000000000;
 432                         --reltime.tv_sec;
 433                       }
 434                     if (reltime.tv_sec >= 0)
 435                       while (__nanosleep_nocancel (&reltime, &reltime) != 0)
 436                         continue;
 437
 438                     return ETIMEDOUT;
 439                   }
 440
 441                 return INTERNAL_SYSCALL_ERRNO (e, __err);
 442               }
 443
 444             oldval = mutex->__data.__lock;
 445
 446             assert (robust || (oldval & FUTEX_OWNER_DIED) == 0);
 447           }
 448
 449         if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
 450           {
 451             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 452
 453             /* We got the mutex.  */
 454             mutex->__data.__count = 1;
 455             /* But it is inconsistent unless marked otherwise.  */
 456             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 457
 458             /* We must not enqueue the mutex before we have acquired it.
 459                Also see comments at ENQUEUE_MUTEX.  */
 460             __asm ("" ::: "memory");
 461             ENQUEUE_MUTEX_PI (mutex);
 462             /* We need to clear op_pending after we enqueue the mutex.  */
 463             __asm ("" ::: "memory");
 464             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 465
 466             /* Note that we deliberately exit here.  If we fall
 467                through to the end of the function __nusers would be
 468                incremented which is not correct because the old owner
 469                has to be discounted.  */
 470             return EOWNERDEAD;
 471           }
 472
 473         if (robust
 474             && __builtin_expect (mutex->__data.__owner
 475                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 476           {
 477             /* This mutex is now not recoverable.  */
 478             mutex->__data.__count = 0;
 479
 480             INTERNAL_SYSCALL_DECL (__err);
 481             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 482                               __lll_private_flag (FUTEX_UNLOCK_PI,
 483                                                   PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),
 484                               0, 0);
 485
 486             /* To the kernel, this will be visible after the kernel has
 487                acquired the mutex in the syscall.  */
 488             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 489             return ENOTRECOVERABLE;
 490           }
 491
 492         mutex->__data.__count = 1;
 493         if (robust)
 494           {
 495             /* We must not enqueue the mutex before we have acquired it.
 496                Also see comments at ENQUEUE_MUTEX.  */
 497             __asm ("" ::: "memory");
 498             ENQUEUE_MUTEX_PI (mutex);
 499             /* We need to clear op_pending after we enqueue the mutex.  */
 500             __asm ("" ::: "memory");
 501             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 502           }
 503         }
 504       break;
 505 #endif  /* __NR_futex.  */
 506
 507     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 508     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 509     case PTHREAD_MUTEX_PP_NORMAL_NP:
 510     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 511       {
 512         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 513
 514         oldval = mutex->__data.__lock;
 515
 516         /* Check whether we already hold the mutex.  */
 517         if (mutex->__data.__owner == id)
 518           {
 519             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 520               return EDEADLK;
 521
 522             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 523               {
 524                 /* Just bump the counter.  */
 525                 if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
 526                   /* Overflow of the counter.  */
 527                   return EAGAIN;
 528
 529                 ++mutex->__data.__count;
 530
 531                 LIBC_PROBE (mutex_timedlock_acquired, 1, mutex);
 532
 533                 return 0;
 534               }
 535           }
 536
 537         int oldprio = -1, ceilval;
 538         do
 539           {
 540             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 541                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 542
 543             if (__pthread_current_priority () > ceiling)
 544               {
 545                 result = EINVAL;
 546               failpp:
 547                 if (oldprio != -1)
 548                   __pthread_tpp_change_priority (oldprio, -1);
 549                 return result;
 550               }
 551
 552             result = __pthread_tpp_change_priority (oldprio, ceiling);
 553             if (result)
 554               return result;
 555
 556             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 557             oldprio = ceiling;
 558
 559             oldval
 560               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 561                                                      ceilval | 1, ceilval);
 562
 563             if (oldval == ceilval)
 564               break;
 565
 566             do
 567               {
 568                 oldval
 569                   = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 570                                                          ceilval | 2,
 571                                                          ceilval | 1);
 572
 573                 if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
 574                   break;
 575
 576                 if (oldval != ceilval)
 577                   {
 578                     /* Reject invalid timeouts.  */
 579                     if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
 580                       {
 581                         result = EINVAL;
 582                         goto failpp;
 583                       }
 584
 585                     struct timeval tv;
 586                     struct timespec rt;
 587
 588                     /* Get the current time.  */
 589                     (void) __gettimeofday (&tv, NULL);
 590
 591                     /* Compute relative timeout.  */
 592                     rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 593                     rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 594                     if (rt.tv_nsec < 0)
 595                       {
 596                         rt.tv_nsec += 1000000000;
 597                         --rt.tv_sec;
 598                       }
 599
 600                     /* Already timed out?  */
 601                     if (rt.tv_sec < 0)
 602                       {
 603                         result = ETIMEDOUT;
 604                         goto failpp;
 605                       }
 606
 607                     lll_futex_timed_wait (&mutex->__data.__lock,
 608                                           ceilval | 2, &rt,
 609                                           PTHREAD_MUTEX_PSHARED (mutex));
 610                   }
 611               }
 612             while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 613                                                         ceilval | 2, ceilval)
 614                    != ceilval);
 615           }
 616         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 617
 618         assert (mutex->__data.__owner == 0);
 619         mutex->__data.__count = 1;
 620       }
 621       break;
 622
 623     default:
 624       /* Correct code cannot set any other type.  */
 625       return EINVAL;
 626     }
 627
 628   if (result == 0)
 629     {
 630       /* Record the ownership.  */
 631       mutex->__data.__owner = id;
 632       ++mutex->__data.__nusers;
 633
 634       LIBC_PROBE (mutex_timedlock_acquired, 1, mutex);
 635     }
 636
 637  out:
 638   return result;
 639 }
 640 weak_alias (__pthread_mutex_timedlock, pthread_mutex_timedlock)