nptl/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 #include <kernel-features.h>
  25
  26
  27 int
  28 __lll_robust_lock_wait (int *futex, int private)
  29 {
  30   int oldval = *futex;
  31   int tid = THREAD_GETMEM (THREAD_SELF, tid);
  32
  33   /* If the futex changed meanwhile try locking again.  */
  34   if (oldval == 0)
  35     goto try;
  36
  37   do
  38     {
  39       if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
  40         return oldval;
  41
  42       int newval = oldval | FUTEX_WAITERS;
  43       if (oldval != newval
  44           && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
  45         continue;
  46
  47       lll_futex_wait (futex, newval, private);
  48
  49     try:
  50       ;
  51     }
  52   while ((oldval = atomic_compare_and_exchange_val_acq (futex,
  53                                                         tid | FUTEX_WAITERS,
  54                                                         0)) != 0);
  55   return 0;
  56 }
  57
  58
  59 int
  60 __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime,
  61                              int private)
  62 {
  63   /* Reject invalid timeouts.  */
  64   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  65     return EINVAL;
  66
  67   int tid = THREAD_GETMEM (THREAD_SELF, tid);
  68   int oldval = *futex;
  69
  70   /* If the futex changed meanwhile try locking again.  */
  71   if (oldval == 0)
  72     goto try;
  73
  74   /* Work around the fact that the kernel rejects negative timeout values
  75      despite them being valid.  */
  76   if (__glibc_unlikely (abstime->tv_sec < 0))
  77     return ETIMEDOUT;
  78
  79   do
  80     {
  81 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
  82      || !defined lll_futex_timed_wait_bitset)
  83       struct timeval tv;
  84       struct timespec rt;
  85
  86       /* Get the current time.  */
  87       (void) __gettimeofday (&tv, NULL);
  88
  89       /* Compute relative timeout.  */
  90       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  91       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  92       if (rt.tv_nsec < 0)
  93         {
  94           rt.tv_nsec += 1000000000;
  95           --rt.tv_sec;
  96         }
  97
  98       /* Already timed out?  */
  99       if (rt.tv_sec < 0)
 100         return ETIMEDOUT;
 101 #endif
 102
 103       /* Wait.  */
 104       if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
 105         return oldval;
 106
 107       int newval = oldval | FUTEX_WAITERS;
 108       if (oldval != newval
 109           && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
 110         continue;
 111
 112 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
 113      || !defined lll_futex_timed_wait_bitset)
 114       lll_futex_timed_wait (futex, newval, &rt, private);
 115 #else
 116       lll_futex_timed_wait_bitset (futex, newval, abstime,
 117                                    FUTEX_CLOCK_REALTIME, private);
 118 #endif
 119
 120     try:
 121       ;
 122     }
 123   while ((oldval = atomic_compare_and_exchange_val_acq (futex,
 124                                                         tid | FUTEX_WAITERS,
 125                                                         0)) != 0);
 126
 127   return 0;
 128 }