nptl/sysdeps/unix/sysv/linux/lowlevelrobustlock.c

   1 /* Copyright (C) 2006-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
   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 <errno.h>
  20 #include <sysdep.h>
  21 #include <lowlevellock.h>
  22 #include <sys/time.h>
  23 #include <pthreadP.h>
  24
  25
  26 int
  27 __lll_robust_lock_wait (int *futex, int private)
  28 {
  29   int oldval = *futex;
  30   int tid = THREAD_GETMEM (THREAD_SELF, tid);
  31
  32   /* If the futex changed meanwhile try locking again.  */
  33   if (oldval == 0)
  34     goto try;
  35
  36   do
  37     {
  38       if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
  39         return oldval;
  40
  41       int newval = oldval | FUTEX_WAITERS;
  42       if (oldval != newval
  43           && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
  44         continue;
  45
  46       lll_futex_wait (futex, newval, private);
  47
  48     try:
  49       ;
  50     }
  51   while ((oldval = atomic_compare_and_exchange_val_acq (futex,
  52                                                         tid | FUTEX_WAITERS,
  53                                                         0)) != 0);
  54   return 0;
  55 }
  56
  57
  58 int
  59 __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime,
  60                              int private)
  61 {
  62   /* Reject invalid timeouts.  */
  63   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  64     return EINVAL;
  65
  66   int tid = THREAD_GETMEM (THREAD_SELF, tid);
  67   int oldval = *futex;
  68
  69   /* If the futex changed meanwhile try locking again.  */
  70   if (oldval == 0)
  71     goto try;
  72
  73   /* Work around the fact that the kernel rejects negative timeout values
  74      despite them being valid.  */
  75   if (__builtin_expect (abstime->tv_sec < 0, 0))
  76     return ETIMEDOUT;
  77
  78   do
  79     {
  80 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
  81      || !defined lll_futex_timed_wait_bitset)
  82       struct timeval tv;
  83       struct timespec rt;
  84
  85       /* Get the current time.  */
  86       (void) __gettimeofday (&tv, NULL);
  87
  88       /* Compute relative timeout.  */
  89       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  90       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  91       if (rt.tv_nsec < 0)
  92         {
  93           rt.tv_nsec += 1000000000;
  94           --rt.tv_sec;
  95         }
  96
  97       /* Already timed out?  */
  98       if (rt.tv_sec < 0)
  99         return ETIMEDOUT;
 100 #endif
 101
 102       /* Wait.  */
 103       if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 104         return oldval;
 105
 106       int newval = oldval | FUTEX_WAITERS;
 107       if (oldval != newval
 108           && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
 109         continue;
 110
 111 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 112      || !defined lll_futex_timed_wait_bitset)
 113       lll_futex_timed_wait (futex, newval, &rt, private);
 114 #else
 115       lll_futex_timed_wait_bitset (futex, newval, abstime,
 116                                    FUTEX_CLOCK_REALTIME, private);
 117 #endif
 118
 119     try:
 120       ;
 121     }
 122   while ((oldval = atomic_compare_and_exchange_val_acq (futex,
 123                                                         tid | FUTEX_WAITERS,
 124                                                         0)) != 0);
 125
 126   return 0;
 127 }