nptl/pthread_setcancelstate.c

   1 /* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   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 "pthreadP.h"
  21 #include <atomic.h>
  22
  23
  24 int
  25 __pthread_setcancelstate (state, oldstate)
  26      int state;
  27      int *oldstate;
  28 {
  29   volatile struct pthread *self;
  30
  31   if (state < PTHREAD_CANCEL_ENABLE || state > PTHREAD_CANCEL_DISABLE)
  32     return EINVAL;
  33
  34   self = THREAD_SELF;
  35
  36   int oldval = THREAD_GETMEM (self, cancelhandling);
  37   while (1)
  38     {
  39       int newval = (state == PTHREAD_CANCEL_DISABLE
  40                     ? oldval | CANCELSTATE_BITMASK
  41                     : oldval & ~CANCELSTATE_BITMASK);
  42
  43       /* Store the old value.  */
  44       if (oldstate != NULL)
  45         *oldstate = ((oldval & CANCELSTATE_BITMASK)
  46                      ? PTHREAD_CANCEL_DISABLE : PTHREAD_CANCEL_ENABLE);
  47
  48       /* Avoid doing unnecessary work.  The atomic operation can
  49          potentially be expensive if the memory has to be locked and
  50          remote cache lines have to be invalidated.  */
  51       if (oldval == newval)
  52         break;
  53
  54       /* Update the cancel handling word.  This has to be done
  55          atomically since other bits could be modified as well.  */
  56       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  57                                               oldval);
  58       if (__builtin_expect (curval == oldval, 1))
  59         {
  60           if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  61             __do_cancel ();
  62
  63           break;
  64         }
  65
  66       /* Prepare for the next round.  */
  67       oldval = curval;
  68     }
  69
  70   return 0;
  71 }
  72 strong_alias (__pthread_setcancelstate, pthread_setcancelstate)