nptl/pthread_setcancelstate.c

   1 /* Copyright (C) 2002-2017 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 (int state, int *oldstate)
  26 {
  27   volatile struct pthread *self;
  28
  29   if (state < PTHREAD_CANCEL_ENABLE || state > PTHREAD_CANCEL_DISABLE)
  30     return EINVAL;
  31
  32   self = THREAD_SELF;
  33
  34   int oldval = THREAD_GETMEM (self, cancelhandling);
  35   while (1)
  36     {
  37       int newval = (state == PTHREAD_CANCEL_DISABLE
  38                     ? oldval | CANCELSTATE_BITMASK
  39                     : oldval & ~CANCELSTATE_BITMASK);
  40
  41       /* Store the old value.  */
  42       if (oldstate != NULL)
  43         *oldstate = ((oldval & CANCELSTATE_BITMASK)
  44                      ? PTHREAD_CANCEL_DISABLE : PTHREAD_CANCEL_ENABLE);
  45
  46       /* Avoid doing unnecessary work.  The atomic operation can
  47          potentially be expensive if the memory has to be locked and
  48          remote cache lines have to be invalidated.  */
  49       if (oldval == newval)
  50         break;
  51
  52       /* Update the cancel handling word.  This has to be done
  53          atomically since other bits could be modified as well.  */
  54       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  55                                               oldval);
  56       if (__glibc_likely (curval == oldval))
  57         {
  58           if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  59             __do_cancel ();
  60
  61           break;
  62         }
  63
  64       /* Prepare for the next round.  */
  65       oldval = curval;
  66     }
  67
  68   return 0;
  69 }
  70 strong_alias (__pthread_setcancelstate, pthread_setcancelstate)
  71 hidden_def (__pthread_setcancelstate)