sysdeps/sparc/sparc32/sem_waitcommon.c

   1 /* sem_waitcommon -- wait on a semaphore, shared code.
   2    Copyright (C) 2003-2017 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 <futex-internal.h>
  23 #include <internaltypes.h>
  24 #include <semaphore.h>
  25 #include <sys/time.h>
  26
  27 #include <pthreadP.h>
  28 #include <shlib-compat.h>
  29 #include <atomic.h>
  30
  31
  32 static void
  33 __sem_wait_32_finish (struct new_sem *sem);
  34
  35 static void
  36 __sem_wait_cleanup (void *arg)
  37 {
  38   struct new_sem *sem = (struct new_sem *) arg;
  39
  40   __sem_wait_32_finish (sem);
  41 }
  42
  43 /* Wait until at least one token is available, possibly with a timeout.
  44    This is in a separate function in order to make sure gcc
  45    puts the call site into an exception region, and thus the
  46    cleanups get properly run.  TODO still necessary?  Other futex_wait
  47    users don't seem to need it.  */
  48 static int
  49 __attribute__ ((noinline))
  50 do_futex_wait (struct new_sem *sem, const struct timespec *abstime)
  51 {
  52   int err;
  53
  54   err = futex_abstimed_wait_cancelable (&sem->value, SEM_NWAITERS_MASK,
  55                                         abstime, sem->private);
  56
  57   return err;
  58 }
  59
  60 /* Fast path: Try to grab a token without blocking.  */
  61 static int
  62 __new_sem_wait_fast (struct new_sem *sem, int definitive_result)
  63 {
  64   unsigned int v;
  65   int ret = 0;
  66
  67   __sparc32_atomic_do_lock24(&sem->pad);
  68
  69   v = sem->value;
  70   if ((v >> SEM_VALUE_SHIFT) == 0)
  71     ret = -1;
  72   else
  73     sem->value = v - (1 << SEM_VALUE_SHIFT);
  74
  75   __sparc32_atomic_do_unlock24(&sem->pad);
  76
  77   return ret;
  78 }
  79
  80 /* Slow path that blocks.  */
  81 static int
  82 __attribute__ ((noinline))
  83 __new_sem_wait_slow (struct new_sem *sem, const struct timespec *abstime)
  84 {
  85   unsigned int v;
  86   int err = 0;
  87
  88   __sparc32_atomic_do_lock24(&sem->pad);
  89
  90   sem->nwaiters++;
  91
  92   pthread_cleanup_push (__sem_wait_cleanup, sem);
  93
  94   /* Wait for a token to be available.  Retry until we can grab one.  */
  95   v = sem->value;
  96   do
  97     {
  98       if (!(v & SEM_NWAITERS_MASK))
  99         sem->value = v | SEM_NWAITERS_MASK;
 100
 101       /* If there is no token, wait.  */
 102       if ((v >> SEM_VALUE_SHIFT) == 0)
 103         {
 104           __sparc32_atomic_do_unlock24(&sem->pad);
 105
 106           err = do_futex_wait(sem, abstime);
 107           if (err == ETIMEDOUT || err == EINTR)
 108             {
 109               __set_errno (err);
 110               err = -1;
 111               goto error;
 112             }
 113           err = 0;
 114
 115           __sparc32_atomic_do_lock24(&sem->pad);
 116
 117           /* We blocked, so there might be a token now.  */
 118           v = sem->value;
 119         }
 120     }
 121   /* If there is no token, we must not try to grab one.  */
 122   while ((v >> SEM_VALUE_SHIFT) == 0);
 123
 124   sem->value = v - (1 << SEM_VALUE_SHIFT);
 125
 126   __sparc32_atomic_do_unlock24(&sem->pad);
 127
 128 error:
 129   pthread_cleanup_pop (0);
 130
 131   __sem_wait_32_finish (sem);
 132
 133   return err;
 134 }
 135
 136 /* Stop being a registered waiter (non-64b-atomics code only).  */
 137 static void
 138 __sem_wait_32_finish (struct new_sem *sem)
 139 {
 140   __sparc32_atomic_do_lock24(&sem->pad);
 141
 142   if (--sem->nwaiters == 0)
 143     sem->value &= ~SEM_NWAITERS_MASK;
 144
 145   __sparc32_atomic_do_unlock24(&sem->pad);
 146 }