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   int oldval;
  40   int newval;
  41   do
  42     {
  43       oldval = pd->cancelhandling;
  44       newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
  45
  46       /* Avoid doing unnecessary work.  The atomic operation can
  47          potentially be expensive if the bug has to be locked and
  48          remote cache lines have to be invalidated.  */
  49       if (oldval == newval)
  50         break;
  51
  52       /* If the cancellation is handled asynchronously just send a
  53          signal.  We avoid this if possible since it's more
  54          expensive.  */
  55       if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  56         {
  57           /* Mark the cancellation as "in progress".  */
  58           atomic_bit_set (&pd->cancelhandling, CANCELING_BIT);
  59
  60           /* The cancellation handler will take care of marking the
  61              thread as canceled.  */
  62           INTERNAL_SYSCALL_DECL (err);
  63
  64           int val = INTERNAL_SYSCALL (tkill, err, 2, pd->tid, SIGCANCEL);
  65
  66           if (INTERNAL_SYSCALL_ERROR_P (val, err))
  67             result = INTERNAL_SYSCALL_ERRNO (val, err);
  68
  69           break;
  70         }
  71     }
  72   /* Mark the thread as canceled.  This has to be done
  73      atomically since other bits could be modified as well.  */
  74   while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
  75                                                oldval));
  76
  77   return result;
  78 }