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   int oldval = THREAD_GETMEM (self, cancelhandling);
  92
  93   while (1)
  94     {
  95       newval = oldval & ~CANCELTYPE_BITMASK;
  96
  97       if (newval == oldval)
  98         break;
  99
 100       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
 101                                               oldval);
 102       if (__builtin_expect (curval == oldval, 1))
 103         break;
 104
 105       /* Prepare the next round.  */
 106       oldval = curval;
 107     }
 108
 109   /* We cannot return when we are being canceled.  Upon return the
 110      thread might be things which would have to be undone.  The
 111      following loop should loop until the cancellation signal is
 112      delivered.  */
 113   while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
 114                            == CANCELING_BITMASK, 0))
 115     {
 116       lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
 117       newval = THREAD_GETMEM (self, cancelhandling);
 118     }
 119 }
 120
 121
 122 void
 123 __libc_cleanup_routine (struct __pthread_cleanup_frame *f)
 124 {
 125   if (f->__do_it)
 126     f->__cancel_routine (f->__cancel_arg);
 127 }
 128
 129 #endif