libpthread/nptl/sysdeps/unix/sysv/linux/sparc/sparc32/sem_wait.c

   1 /* sem_wait -- wait on a semaphore.  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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <internaltypes.h>
  24 #include <semaphore.h>
  25
  26 #include <pthreadP.h>
  27
  28
  29 void
  30 attribute_hidden
  31 __sem_wait_cleanup (void *arg)
  32 {
  33   struct sparc_new_sem *isem = (struct sparc_new_sem *) arg;
  34
  35   if (__atomic_is_v9)
  36     atomic_decrement (&isem->nwaiters);
  37   else
  38     {
  39       __sparc32_atomic_do_lock24 (&isem->lock);
  40       isem->nwaiters--;
  41       __sparc32_atomic_do_unlock24 (&isem->lock);
  42     }
  43 }
  44
  45
  46 int
  47 sem_wait (sem_t *sem)
  48 {
  49   struct sparc_new_sem *isem = (struct sparc_new_sem *) sem;
  50   int err;
  51   int val;
  52
  53   if (__atomic_is_v9)
  54     val = atomic_decrement_if_positive (&isem->value);
  55   else
  56     {
  57       __sparc32_atomic_do_lock24 (&isem->lock);
  58       val = isem->value;
  59       if (val > 0)
  60         isem->value = val - 1;
  61       else
  62         isem->nwaiters++;
  63       __sparc32_atomic_do_unlock24 (&isem->lock);
  64     }
  65
  66   if (val > 0)
  67     return 0;
  68
  69   if (__atomic_is_v9)
  70     atomic_increment (&isem->nwaiters);
  71   else
  72     /* Already done above while still holding isem->lock.  */;
  73
  74   pthread_cleanup_push (__sem_wait_cleanup, isem);
  75
  76   while (1)
  77     {
  78       /* Enable asynchronous cancellation.  Required by the standard.  */
  79       int oldtype = __pthread_enable_asynccancel ();
  80
  81       err = lll_futex_wait (&isem->value, 0,
  82                             isem->private ^ FUTEX_PRIVATE_FLAG);
  83
  84       /* Disable asynchronous cancellation.  */
  85       __pthread_disable_asynccancel (oldtype);
  86
  87       if (err != 0 && err != -EWOULDBLOCK)
  88         {
  89           __set_errno (-err);
  90           err = -1;
  91           break;
  92         }
  93
  94       if (__atomic_is_v9)
  95         val = atomic_decrement_if_positive (&isem->value);
  96       else
  97         {
  98           __sparc32_atomic_do_lock24 (&isem->lock);
  99           val = isem->value;
 100           if (val > 0)
 101             isem->value = val - 1;
 102           __sparc32_atomic_do_unlock24 (&isem->lock);
 103         }
 104
 105       if (val > 0)
 106         {
 107           err = 0;
 108           break;
 109         }
 110     }
 111
 112   pthread_cleanup_pop (0);
 113
 114   if (__atomic_is_v9)
 115     atomic_decrement (&isem->nwaiters);
 116   else
 117     {
 118       __sparc32_atomic_do_lock24 (&isem->lock);
 119       isem->nwaiters--;
 120       __sparc32_atomic_do_unlock24 (&isem->lock);
 121     }
 122
 123   return err;
 124 }