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

   1 /* low level locking for pthread library.  Generic futex-using version.
   2    Copyright (C) 2003 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <errno.h>
  22 #include <sysdep.h>
  23 #include <lowlevellock.h>
  24 #include <sys/time.h>
  25
  26
  27 void
  28 __lll_lock_wait (int *futex)
  29 {
  30   do
  31     {
  32       int oldval = atomic_compare_and_exchange_val_acq (futex, 2, 1);
  33       if (oldval != 0)
  34         lll_futex_wait (futex, 2);
  35     }
  36   while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0);
  37 }
  38
  39
  40 int
  41 __lll_timedlock_wait (int *futex, const struct timespec *abstime)
  42 {
  43   /* Reject invalid timeouts.  */
  44   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  45     return EINVAL;
  46
  47   do
  48     {
  49       struct timeval tv;
  50       struct timespec rt;
  51
  52       /* Get the current time.  */
  53       (void) __gettimeofday (&tv, NULL);
  54
  55       /* Compute relative timeout.  */
  56       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  57       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  58       if (rt.tv_nsec < 0)
  59         {
  60           rt.tv_nsec += 1000000000;
  61           --rt.tv_sec;
  62         }
  63
  64       /* Already timed out?  */
  65       if (rt.tv_sec < 0)
  66         return ETIMEDOUT;
  67
  68       /* Wait.  */
  69       int oldval = atomic_compare_and_exchange_val_acq (futex, 2, 1);
  70       if (oldval != 0)
  71         lll_futex_timed_wait (futex, 2, &rt);
  72     }
  73   while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0);
  74
  75   return 0;
  76 }
  77
  78
  79 /* These don't get included in libc.so  */
  80 #ifdef IS_IN_libpthread
  81 int
  82 lll_unlock_wake_cb (int *futex)
  83 {
  84   int val = atomic_exchange_rel (futex, 0);
  85
  86   if (__builtin_expect (val > 1, 0))
  87     lll_futex_wake (futex, 1);
  88
  89   return 0;
  90 }
  91
  92
  93 int
  94 __lll_timedwait_tid (int *tidp, const struct timespec *abstime)
  95 {
  96   int tid;
  97
  98   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  99     return EINVAL;
 100
 101   /* Repeat until thread terminated.  */
 102   while ((tid = *tidp) != 0)
 103     {
 104       struct timeval tv;
 105       struct timespec rt;
 106
 107       /* Get the current time.  */
 108       (void) __gettimeofday (&tv, NULL);
 109
 110       /* Compute relative timeout.  */
 111       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 112       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 113       if (rt.tv_nsec < 0)
 114         {
 115           rt.tv_nsec += 1000000000;
 116           --rt.tv_sec;
 117         }
 118
 119       /* Already timed out?  */
 120       if (rt.tv_sec < 0)
 121         return ETIMEDOUT;
 122
 123       /* Wait until thread terminates.  */
 124       if (lll_futex_timed_wait (tidp, tid, &rt) == -ETIMEDOUT)
 125         return ETIMEDOUT;
 126     }
 127
 128   return 0;
 129 }
 130
 131 #endif