ports/sysdeps/unix/sysv/linux/arm/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
   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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <sysdep.h>
  21 #include <lowlevellock.h>
  22 #include <sys/time.h>
  23
  24 void
  25 __lll_lock_wait_private (int *futex)
  26 {
  27   do
  28     {
  29       int oldval = atomic_compare_and_exchange_val_acq (futex, 2, 1);
  30       if (oldval != 0)
  31         lll_futex_wait (futex, 2, LLL_PRIVATE);
  32     }
  33   while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0);
  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   do
  43     {
  44       int oldval = atomic_compare_and_exchange_val_acq (futex, 2, 1);
  45       if (oldval != 0)
  46         lll_futex_wait (futex, 2, private);
  47     }
  48   while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0);
  49 }
  50
  51
  52 int
  53 __lll_timedlock_wait (int *futex, const struct timespec *abstime, int private)
  54 {
  55   struct timespec rt;
  56
  57   /* Reject invalid timeouts.  */
  58   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
  59     return EINVAL;
  60
  61   /* Upgrade the lock.  */
  62   if (atomic_exchange_acq (futex, 2) == 0)
  63     return 0;
  64
  65   do
  66     {
  67       struct timeval tv;
  68
  69       /* Get the current time.  */
  70       (void) __gettimeofday (&tv, NULL);
  71
  72       /* Compute relative timeout.  */
  73       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
  74       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
  75       if (rt.tv_nsec < 0)
  76         {
  77           rt.tv_nsec += 1000000000;
  78           --rt.tv_sec;
  79         }
  80
  81       /* Already timed out?  */
  82       if (rt.tv_sec < 0)
  83         return ETIMEDOUT;
  84
  85       // XYZ: Lost the lock to check whether it was private.
  86       lll_futex_timed_wait (futex, 2, &rt, private);
  87     }
  88   while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0);
  89
  90   return 0;
  91 }
  92
  93
  94 int
  95 __lll_timedwait_tid (int *tidp, const struct timespec *abstime)
  96 {
  97   int tid;
  98
  99   if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
 100     return EINVAL;
 101
 102   /* Repeat until thread terminated.  */
 103   while ((tid = *tidp) != 0)
 104     {
 105       struct timeval tv;
 106       struct timespec rt;
 107
 108       /* Get the current time.  */
 109       (void) __gettimeofday (&tv, NULL);
 110
 111       /* Compute relative timeout.  */
 112       rt.tv_sec = abstime->tv_sec - tv.tv_sec;
 113       rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
 114       if (rt.tv_nsec < 0)
 115         {
 116           rt.tv_nsec += 1000000000;
 117           --rt.tv_sec;
 118         }
 119
 120       /* Already timed out?  */
 121       if (rt.tv_sec < 0)
 122         return ETIMEDOUT;
 123
 124       /* Wait until thread terminates.  */
 125       // XYZ: Lost the lock to check whether it was private.
 126       if (lll_futex_timed_wait (tidp, tid, &rt, LLL_SHARED) == -ETIMEDOUT)
 127         return ETIMEDOUT;
 128     }
 129
 130   return 0;
 131 }
 132 #endif