nptl/cancellation.c

   1 /* Copyright (C) 2002-2019 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 <setjmp.h>
  20 #include <stdlib.h>
  21 #include "pthreadP.h"
  22 #include <futex-internal.h>
  23
  24
  25 /* The next two functions are similar to pthread_setcanceltype() but
  26    more specialized for the use in the cancelable functions like write().
  27    They do not need to check parameters etc.  */
  28 int
  29 attribute_hidden
  30 __pthread_enable_asynccancel (void)
  31 {
  32   struct pthread *self = THREAD_SELF;
  33   int oldval = THREAD_GETMEM (self, cancelhandling);
  34
  35   while (1)
  36     {
  37       int newval = oldval | CANCELTYPE_BITMASK;
  38
  39       if (newval == oldval)
  40         break;
  41
  42       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  43                                               oldval);
  44       if (__glibc_likely (curval == oldval))
  45         {
  46           if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  47             {
  48               THREAD_SETMEM (self, result, PTHREAD_CANCELED);
  49               __do_cancel ();
  50             }
  51
  52           break;
  53         }
  54
  55       /* Prepare the next round.  */
  56       oldval = curval;
  57     }
  58
  59   return oldval;
  60 }
  61
  62
  63 void
  64 attribute_hidden
  65 __pthread_disable_asynccancel (int oldtype)
  66 {
  67   /* If asynchronous cancellation was enabled before we do not have
  68      anything to do.  */
  69   if (oldtype & CANCELTYPE_BITMASK)
  70     return;
  71
  72   struct pthread *self = THREAD_SELF;
  73   int newval;
  74
  75   int oldval = THREAD_GETMEM (self, cancelhandling);
  76
  77   while (1)
  78     {
  79       newval = oldval & ~CANCELTYPE_BITMASK;
  80
  81       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  82                                               oldval);
  83       if (__glibc_likely (curval == oldval))
  84         break;
  85
  86       /* Prepare the next round.  */
  87       oldval = curval;
  88     }
  89
  90   /* We cannot return when we are being canceled.  Upon return the
  91      thread might be things which would have to be undone.  The
  92      following loop should loop until the cancellation signal is
  93      delivered.  */
  94   while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
  95                            == CANCELING_BITMASK, 0))
  96     {
  97       futex_wait_simple ((unsigned int *) &self->cancelhandling, newval,
  98                          FUTEX_PRIVATE);
  99       newval = THREAD_GETMEM (self, cancelhandling);
 100     }
 101 }