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