nptl/libc-cancellation.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 <setjmp.h>
  21 #include <stdlib.h>
  22 #include "pthreadP.h"
  23 #include "atomic.h"
  24
  25
  26 #ifndef NOT_IN_libc
  27
  28 /* The next two functions are similar to pthread_setcanceltype() but
  29    more specialized for the use in the cancelable functions like write().
  30    They do not need to check parameters etc.  */
  31 int
  32 attribute_hidden
  33 __libc_enable_asynccancel (void)
  34 {
  35   struct pthread *self = THREAD_SELF;
  36   int oldval;
  37
  38   while (1)
  39     {
  40       oldval = THREAD_GETMEM (self, cancelhandling);
  41       int newval = oldval | CANCELTYPE_BITMASK;
  42
  43       if (__builtin_expect ((oldval & CANCELED_BITMASK) != 0, 0))
  44         {
  45           /* If we are already exiting stop right here.  */
  46           if ((oldval & EXITING_BITMASK) != 0)
  47             break;
  48
  49           if (atomic_compare_and_exchange_acq (&self->cancelhandling, newval,
  50                                                oldval) != 0)
  51             /* Somebody else modified the word, try again.  */
  52             continue;
  53
  54           THREAD_SETMEM (self, result, PTHREAD_CANCELED);
  55
  56           /* The thread is exiting now.  */
  57           atomic_bit_set (&self->cancelhandling, EXITING_BIT);
  58
  59           __do_cancel ();
  60
  61           /* NOTREACHED */
  62         }
  63
  64       if (atomic_compare_and_exchange_acq (&self->cancelhandling, newval,
  65                                            oldval) == 0)
  66         break;
  67     }
  68
  69   return oldval;
  70 }
  71
  72
  73 void
  74 internal_function attribute_hidden
  75 __libc_disable_asynccancel (int oldtype)
  76 {
  77   /* If asynchronous cancellation was enabled before we do not have
  78      anything to do.  */
  79   if (oldtype & CANCELTYPE_BITMASK)
  80     return;
  81
  82   struct pthread *self = THREAD_SELF;
  83
  84   while (1)
  85     {
  86       int oldval = THREAD_GETMEM (self, cancelhandling);
  87       int newval = oldval & ~CANCELTYPE_BITMASK;
  88
  89       if (newval == oldval)
  90         break;
  91
  92       if (atomic_compare_and_exchange_acq (&self->cancelhandling, newval,
  93                                            oldval) == 0)
  94         break;
  95     }
  96 }
  97
  98 #endif