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

   1 /* low level locking for pthread library.  Generic futex-using version.
   2    Copyright (C) 2003, 2007 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_private (int *futex)
  29 {
  30   if (*futex == 2)
  31     lll_futex_wait (futex, 2, LLL_PRIVATE);
  32
  33   while (atomic_exchange_acq (futex, 2) != 0)
  34     lll_futex_wait (futex, 2, LLL_PRIVATE);
  35 }
  36
  37
  38 /* These functions don't get included in libc.so  */
  39 #ifdef IS_IN_libpthread
  40 void
  41 __lll_lock_wait (int *futex, int private)
  42 {
  43   if (*futex == 2)
  44     lll_futex_wait (futex, 2, private);
  45
  46   while (atomic_exchange_acq (futex, 2) != 0)
  47     lll_futex_wait (futex, 2, private);
  48 }
  49
  50
  51 int
  52 __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private)
  53 {
  54   /* Reject invalid timeouts.  */
  55   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  56     return EINVAL;
  57
  58   /* Try locking.  */
  59   while (atomic_exchange_acq (futex, 2) != 0)
  60     {
  61       struct timeval tv;
  62
  63       /* Get the current time.  */
  64       (void) __gettimeofday (&tv, NULL);
  65
  66       /* Compute relative timeout.  */
  67       struct timespec rt;
  68       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  69       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  70       if (rt.tv_nsec < 0)
  71         {
  72           rt.tv_nsec += 1000000000;
  73           --rt.tv_sec;
  74         }
  75
  76       if (rt.tv_sec < 0)
  77         return ETIMEDOUT;
  78
  79       /* Wait.  */
  80       lll_futex_timed_wait (futex, 2, &rt, private);
  81     }
  82
  83   return 0;
  84 }
  85
  86
  87 int
  88 __lll_timedwait_tid (int *tidp, const struct timespec *abstime)
  89 {
  90   int tid;
  91
  92   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  93     return EINVAL;
  94
  95   /* Repeat until thread terminated.  */
  96   while ((tid = *tidp) != 0)
  97     {
  98       struct timeval tv;
  99       struct timespec rt;
 100
 101       /* Get the current time.  */
 102       (void) __gettimeofday (&tv, NULL);
 103
 104       /* Compute relative timeout.  */
 105       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 106       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 107       if (rt.tv_nsec < 0)
 108         {
 109           rt.tv_nsec += 1000000000;
 110           --rt.tv_sec;
 111         }
 112
 113       /* Already timed out?  */
 114       if (rt.tv_sec < 0)
 115         return ETIMEDOUT;
 116
 117       /* Wait until thread terminates.  The kernel so far does not use
 118          the private futex operations for this.  */
 119       if (lll_futex_timed_wait (tidp, tid, &rt, LLL_SHARED) == -ETIMEDOUT)
 120         return ETIMEDOUT;
 121     }
 122
 123   return 0;
 124 }
 125 #endif