nptl/libc-cancellation.c

   1 /* Copyright (C) 2002, 2003, 2005, 2009 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 #include <bits/libc-lock.h>
  25
  26
  27 #ifndef NOT_IN_libc
  28
  29 /* The next two functions are similar to pthread_setcanceltype() but
  30    more specialized for the use in the cancelable functions like write().
  31    They do not need to check parameters etc.  */
  32 int
  33 attribute_hidden
  34 __libc_enable_asynccancel (void)
  35 {
  36   struct pthread *self = THREAD_SELF;
  37   int oldval = THREAD_GETMEM (self, cancelhandling);
  38
  39   while (1)
  40     {
  41       int newval = oldval | CANCELTYPE_BITMASK;
  42
  43       if (__builtin_expect ((oldval & CANCELED_BITMASK) != 0, 0))
  44         {
  45           /* If we are already exiting or if PTHREAD_CANCEL_DISABLED,
  46              stop right here.  */
  47           if ((oldval & (EXITING_BITMASK | CANCELSTATE_BITMASK)) != 0)
  48             break;
  49
  50           int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
  51                                                   newval, oldval);
  52           if (__builtin_expect (curval != oldval, 0))
  53             {
  54               /* Somebody else modified the word, try again.  */
  55               oldval = curval;
  56               continue;
  57             }
  58
  59           THREAD_SETMEM (self, result, PTHREAD_CANCELED);
  60
  61           __do_cancel ();
  62
  63           /* NOTREACHED */
  64         }
  65
  66       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
  67                                               oldval);
  68       if (__builtin_expect (curval == oldval, 1))
  69         break;
  70
  71       /* Prepare the next round.  */
  72       oldval = curval;
  73     }
  74
  75   return oldval;
  76 }
  77
  78
  79 void
  80 internal_function attribute_hidden
  81 __libc_disable_asynccancel (int oldtype)
  82 {
  83   /* If asynchronous cancellation was enabled before we do not have
  84      anything to do.  */
  85   if (oldtype & CANCELTYPE_BITMASK)
  86     return;
  87
  88   struct pthread *self = THREAD_SELF;
  89   int newval;
  90
  91 #ifdef THREAD_ATOMIC_AND
  92   THREAD_ATOMIC_AND (self, cancelhandling, ~CANCELTYPE_BITMASK);
  93   newval = THREAD_GETMEM (self, cancelhandling);
  94 #else
  95   int oldval = THREAD_GETMEM (self, cancelhandling);
  96
  97   while (1)
  98     {
  99       newval = oldval & ~CANCELTYPE_BITMASK;
 100
 101       if (newval == oldval)
 102         break;
 103
 104       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
 105                                               oldval);
 106       if (__builtin_expect (curval == oldval, 1))
 107         break;
 108
 109       /* Prepare the next round.  */
 110       oldval = curval;
 111     }
 112 #endif
 113
 114   /* We cannot return when we are being canceled.  Upon return the
 115      thread might be things which would have to be undone.  The
 116      following loop should loop until the cancellation signal is
 117      delivered.  */
 118   while (__builtin_expect (newval & CANCELED_BITMASK, 0))
 119     {
 120       lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
 121       newval = THREAD_GETMEM (self, cancelhandling);
 122     }
 123 }
 124
 125
 126 void
 127 __libc_cleanup_routine (struct __pthread_cleanup_frame *f)
 128 {
 129   if (f->__do_it)
 130     f->__cancel_routine (f->__cancel_arg);
 131 }
 132
 133 #endif