nptl/pthread_setcanceltype.c

   1 /* Copyright (C) 2002-2021 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    <https://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   volatile struct pthread *self = THREAD_SELF;
  31
  32   int oldval = THREAD_GETMEM (self, cancelhandling);
  33   while (1)
  34     {
  35       int newval = (type == PTHREAD_CANCEL_ASYNCHRONOUS
  36                     ? oldval | CANCELTYPE_BITMASK
  37                     : oldval & ~CANCELTYPE_BITMASK);
  38
  39       /* Store the old value.  */
  40       if (oldtype != NULL)
  41         *oldtype = ((oldval & CANCELTYPE_BITMASK)
  42                     ? PTHREAD_CANCEL_ASYNCHRONOUS : PTHREAD_CANCEL_DEFERRED);
  43
  44       /* Avoid doing unnecessary work.  The atomic operation can
  45          potentially be expensive if the memory has to be locked and
  46          remote cache lines have to be invalidated.  */
  47       if (oldval == newval)
  48         break;
  49
  50       /* Update the cancel handling word.  This has to be done
  51          atomically since other bits could be modified as well.  */
  52       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  53                                               oldval);
  54       if (__glibc_likely (curval == oldval))
  55         {
  56           if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  57             {
  58               THREAD_SETMEM (self, result, PTHREAD_CANCELED);
  59               __do_cancel ();
  60             }
  61
  62           break;
  63         }
  64
  65       /* Prepare for the next round.  */
  66       oldval = curval;
  67     }
  68
  69   return 0;
  70 }
  71 libc_hidden_def (__pthread_setcanceltype)
  72 weak_alias (__pthread_setcanceltype, pthread_setcanceltype)