nptl/lowlevellock.c

   1 /* low level locking for pthread library.  Generic futex-using version.
   2    Copyright (C) 2003-2014 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <sys/time.h>
  24 #include <atomic.h>
  25
  26 void
  27 __lll_lock_wait_private (int *futex)
  28 {
  29   if (*futex == 2)
  30     lll_futex_wait (futex, 2, LLL_PRIVATE);
  31
  32   while (atomic_exchange_acq (futex, 2) != 0)
  33     lll_futex_wait (futex, 2, LLL_PRIVATE);
  34 }
  35
  36
  37 /* These functions don't get included in libc.so  */
  38 #ifdef IS_IN_libpthread
  39 void
  40 __lll_lock_wait (int *futex, int private)
  41 {
  42   if (*futex == 2)
  43     lll_futex_wait (futex, 2, private);
  44
  45   while (atomic_exchange_acq (futex, 2) != 0)
  46     lll_futex_wait (futex, 2, private);
  47 }
  48
  49
  50 int
  51 __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private)
  52 {
  53   /* Reject invalid timeouts.  */
  54   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  55     return EINVAL;
  56
  57   /* Try locking.  */
  58   while (atomic_exchange_acq (futex, 2) != 0)
  59     {
  60       struct timeval tv;
  61
  62       /* Get the current time.  */
  63       (void) __gettimeofday (&tv, NULL);
  64
  65       /* Compute relative timeout.  */
  66       struct timespec rt;
  67       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  68       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  69       if (rt.tv_nsec < 0)
  70         {
  71           rt.tv_nsec += 1000000000;
  72           --rt.tv_sec;
  73         }
  74
  75       if (rt.tv_sec < 0)
  76         return ETIMEDOUT;
  77
  78       /* Wait.  */
  79       lll_futex_timed_wait (futex, 2, &rt, private);
  80     }
  81
  82   return 0;
  83 }
  84
  85
  86 int
  87 __lll_timedwait_tid (int *tidp, const struct timespec *abstime)
  88 {
  89   int tid;
  90
  91   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  92     return EINVAL;
  93
  94   /* Repeat until thread terminated.  */
  95   while ((tid = *tidp) != 0)
  96     {
  97       struct timeval tv;
  98       struct timespec rt;
  99
 100       /* Get the current time.  */
 101       (void) __gettimeofday (&tv, NULL);
 102
 103       /* Compute relative timeout.  */
 104       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 105       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 106       if (rt.tv_nsec < 0)
 107         {
 108           rt.tv_nsec += 1000000000;
 109           --rt.tv_sec;
 110         }
 111
 112       /* Already timed out?  */
 113       if (rt.tv_sec < 0)
 114         return ETIMEDOUT;
 115
 116       /* Wait until thread terminates.  The kernel so far does not use
 117          the private futex operations for this.  */
 118       if (lll_futex_timed_wait (tidp, tid, &rt, LLL_SHARED) == -ETIMEDOUT)
 119         return ETIMEDOUT;
 120     }
 121
 122   return 0;
 123 }
 124 #endif