nptl/pthread_cancel.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 <errno.h>
  21 #include <signal.h>
  22 #include "pthreadP.h"
  23 #include "atomic.h"
  24 #include <sysdep.h>
  25
  26
  27 int
  28 pthread_cancel (th)
  29      pthread_t th;
  30 {
  31   volatile struct pthread *pd = (volatile struct pthread *) th;
  32
  33   /* Make sure the descriptor is valid.  */
  34   if (INVALID_TD_P (pd))
  35     /* Not a valid thread handle.  */
  36     return ESRCH;
  37
  38   int result = 0;
  39   while (1)
  40     {
  41       int oldval = pd->cancelhandling;
  42       int newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
  43
  44       /* Avoid doing unnecessary work.  The atomic operation can
  45          potentially be expensive if the bug has to be locked and
  46          remote cache lines have to be invalidated.  */
  47       if (oldval == newval)
  48         break;
  49
  50       /* If the cancellation is handled asynchronously just send a
  51          signal.  We avoid this if possible since it's more
  52          expensive.  */
  53       if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  54         {
  55           /* Mark the cancellation as "in progress".  */
  56           atomic_bit_set (&pd->cancelhandling, CANCELING_BIT);
  57
  58           /* The cancellation handler will take care of marking the
  59              thread as canceled.  */
  60           INTERNAL_SYSCALL_DECL (err);
  61
  62           int val = INTERNAL_SYSCALL (tkill, err, 2, pd->tid, SIGCANCEL);
  63
  64           if (INTERNAL_SYSCALL_ERROR_P (val, err))
  65             result = INTERNAL_SYSCALL_ERRNO (val, err);
  66
  67           break;
  68         }
  69
  70       /* Mark the thread as canceled.  This has to be done
  71          atomically since other bits could be modified as well.  */
  72       if (atomic_compare_and_exchange_acq (&pd->cancelhandling, newval,
  73                                            oldval) == 0)
  74         break;
  75     }
  76
  77   return result;
  78 }