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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include "pthreadP.h"
  22 #include <atomic.h>
  23
  24
  25 int
  26 __pthread_setcancelstate (state, oldstate)
  27      int state;
  28      int *oldstate;
  29 {
  30   volatile struct pthread *self;
  31
  32   if (state < PTHREAD_CANCEL_ENABLE || state > PTHREAD_CANCEL_DISABLE)
  33     return EINVAL;
  34
  35   self = THREAD_SELF;
  36
  37   int oldval = THREAD_GETMEM (self, cancelhandling);
  38   while (1)
  39     {
  40       int newval = (state == PTHREAD_CANCEL_DISABLE
  41                     ? oldval | CANCELSTATE_BITMASK
  42                     : oldval & ~CANCELSTATE_BITMASK);
  43
  44       /* Store the old value.  */
  45       if (oldstate != NULL)
  46         *oldstate = ((oldval & CANCELSTATE_BITMASK)
  47                      ? PTHREAD_CANCEL_DISABLE : PTHREAD_CANCEL_ENABLE);
  48
  49       /* Avoid doing unnecessary work.  The atomic operation can
  50          potentially be expensive if the memory has to be locked and
  51          remote cache lines have to be invalidated.  */
  52       if (oldval == newval)
  53         break;
  54
  55       /* Update the cancel handling word.  This has to be done
  56          atomically since other bits could be modified as well.  */
  57       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  58                                               oldval);
  59       if (__builtin_expect (curval == oldval, 1))
  60         {
  61           if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  62             __do_cancel ();
  63
  64           break;
  65         }
  66
  67       /* Prepare for the next round.  */
  68       oldval = curval;
  69     }
  70
  71   return 0;
  72 }
  73 strong_alias (__pthread_setcancelstate, pthread_setcancelstate)