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, 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 (__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, 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   do
  75     {
  76       struct timeval tv;
  77       struct timespec rt;
  78
  79       /* Get the current time.  */
  80       (void) __gettimeofday (&tv, NULL);
  81
  82       /* Compute relative timeout.  */
  83       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  84       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  85       if (rt.tv_nsec < 0)
  86         {
  87           rt.tv_nsec += 1000000000;
  88           --rt.tv_sec;
  89         }
  90
  91       /* Already timed out?  */
  92       if (rt.tv_sec < 0)
  93         return ETIMEDOUT;
  94
  95       /* Wait.  */
  96       if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
  97         return oldval;
  98
  99       int newval = oldval | FUTEX_WAITERS;
 100       if (oldval != newval
 101           && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
 102         continue;
 103
 104       lll_futex_timed_wait (futex, newval, &rt, private);
 105
 106     try:
 107       ;
 108     }
 109   while ((oldval = atomic_compare_and_exchange_val_acq (futex,
 110                                                         tid | FUTEX_WAITERS,
 111                                                         0)) != 0);
 112
 113   return 0;
 114 }