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

   1 /* Copyright (C) 2006, 2007 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <sys/time.h>
  24 #include <pthreadP.h>
  25
  26
  27 int
  28 __lll_robust_lock_wait (int *futex)
  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 (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
  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);
  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 {
  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   do
  74     {
  75       struct timeval tv;
  76       struct timespec rt;
  77
  78       /* Get the current time.  */
  79       (void) __gettimeofday (&tv, NULL);
  80
  81       /* Compute relative timeout.  */
  82       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  83       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  84       if (rt.tv_nsec < 0)
  85         {
  86           rt.tv_nsec += 1000000000;
  87           --rt.tv_sec;
  88         }
  89
  90       /* Already timed out?  */
  91       if (rt.tv_sec < 0)
  92         return ETIMEDOUT;
  93
  94       /* Wait.  */
  95       if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
  96         return oldval;
  97
  98       int newval = oldval | FUTEX_WAITERS;
  99       if (oldval != newval
 100           && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
 101         continue;
 102
 103       lll_futex_timed_wait (futex, newval, &rt);
 104
 105     try:
 106       ;
 107     }
 108   while ((oldval = atomic_compare_and_exchange_val_acq (futex,
 109                                                         tid | FUTEX_WAITERS,
 110                                                         0)) != 0);
 111
 112   return 0;
 113 }