1: /* Copyright (C) 2002, 2003, 2004 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: #include <kernel-features.h>
   26: 
   27: 
   28: int
   29: pthread_cancel (th)
   30:      pthread_t th;
   31: {
   32:   volatile struct pthread *pd = (volatile struct pthread *) th;
   33: 
   34:   /* Make sure the descriptor is valid.  */
   35:   if (INVALID_TD_P (pd))
   36:     /* Not a valid thread handle.  */
   37:     return ESRCH;
   38: 
   39: #ifdef SHARED
   40:   pthread_cancel_init ();
   41: #endif
   42:   int result = 0;
   43:   int oldval;
   44:   int newval;
   45:   do
   46:     {
   47:       oldval = pd->cancelhandling;
   48:       newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
   49: 
   50:       /* Avoid doing unnecessary work.  The atomic operation can
   51:          potentially be expensive if the bug has to be locked and
   52:          remote cache lines have to be invalidated.  */
   53:       if (oldval == newval)
   54:         break;
   55: 
   56:       /* If the cancellation is handled asynchronously just send a
   57:          signal.  We avoid this if possible since it's more
   58:          expensive.  */
   59:       if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
   60:         {
   61:           /* Mark the cancellation as "in progress".  */
   62:           atomic_bit_set (&pd->cancelhandling, CANCELING_BIT);
   63: 
   64:           /* The cancellation handler will take care of marking the
   65:              thread as canceled.  */
   66:           INTERNAL_SYSCALL_DECL (err);
   67: 
   68:           /* One comment: The PID field in the TCB can temporarily be
   69:              changed (in fork).  But this must not affect this code
   70:              here.  Since this function would have to be called while
   71:              the thread is executing fork, it would have to happen in
   72:              a signal handler.  But this is no allowed, pthread_cancel
   73:              is not guaranteed to be async-safe.  */
   74:           int val;
   75: #if __ASSUME_TGKILL
   76:           val = INTERNAL_SYSCALL (tgkill, err, 3,
   77:                                   THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
   78:                                   SIGCANCEL);
   79: #else
   80: # ifdef __NR_tgkill
   81:           val = INTERNAL_SYSCALL (tgkill, err, 3,
   82:                                   THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
   83:                                   SIGCANCEL);
   84:           if (INTERNAL_SYSCALL_ERROR_P (val, err)
   85:               && INTERNAL_SYSCALL_ERRNO (val, err) == ENOSYS)
   86: # endif
   87:             val = INTERNAL_SYSCALL (tkill, err, 2, pd->tid, SIGCANCEL);
   88: #endif
   89: 
   90:           if (INTERNAL_SYSCALL_ERROR_P (val, err))
   91:             result = INTERNAL_SYSCALL_ERRNO (val, err);
   92: 
   93:           break;
   94:         }
   95:     }
   96:   /* Mark the thread as canceled.  This has to be done
   97:      atomically since other bits could be modified as well.  */
   98:   while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
   99:                                                oldval));
  100: 
  101:   return result;
  102: }
  103: 
  104: PTHREAD_STATIC_FN_REQUIRE (pthread_create)