nptl/pthread_setcanceltype.c

   1 /* Copyright (C) 2002-2015 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_setcanceltype (int type, int *oldtype)
  26 {
  27   if (type < PTHREAD_CANCEL_DEFERRED || type > PTHREAD_CANCEL_ASYNCHRONOUS)
  28     return EINVAL;
  29
  30 #ifndef SIGCANCEL
  31   if (type == PTHREAD_CANCEL_ASYNCHRONOUS)
  32     return ENOTSUP;
  33 #endif
  34
  35   volatile struct pthread *self = THREAD_SELF;
  36
  37   int oldval = THREAD_GETMEM (self, cancelhandling);
  38   while (1)
  39     {
  40       int newval = (type == PTHREAD_CANCEL_ASYNCHRONOUS
  41                     ? oldval | CANCELTYPE_BITMASK
  42                     : oldval & ~CANCELTYPE_BITMASK);
  43
  44       /* Store the old value.  */
  45       if (oldtype != NULL)
  46         *oldtype = ((oldval & CANCELTYPE_BITMASK)
  47                     ? PTHREAD_CANCEL_ASYNCHRONOUS : PTHREAD_CANCEL_DEFERRED);
  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 (__glibc_likely (curval == oldval))
  60         {
  61           if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  62             {
  63               THREAD_SETMEM (self, result, PTHREAD_CANCELED);
  64               __do_cancel ();
  65             }
  66
  67           break;
  68         }
  69
  70       /* Prepare for the next round.  */
  71       oldval = curval;
  72     }
  73
  74   return 0;
  75 }
  76 strong_alias (__pthread_setcanceltype, pthread_setcanceltype)