/* Copyright (C) 2002-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <errno.h>

#include <signal.h>

#include <stdlib.h>

#include "pthreadP.h"

#include <atomic.h>

#include <sysdep.h>

#include <unistd.h>

int

__pthread_cancel (pthread_t th)

{

  volatile struct pthread *pd = (volatile struct pthread *) th;

  /* Make sure the descriptor is valid.  */

  if (INVALID_TD_P (pd))

    /* Not a valid thread handle.  */

    return ESRCH;

#ifdef SHARED

  pthread_cancel_init ();

#endif

  int result = 0;

  int oldval;

  int newval;

  do

    {

    again:

      oldval = pd->cancelhandling;

      newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;

      /* Avoid doing unnecessary work.  The atomic operation can

	 potentially be expensive if the bug has to be locked and

	 remote cache lines have to be invalidated.  */

      if (oldval == newval)

	break;

      /* If the cancellation is handled asynchronously just send a

	 signal.  We avoid this if possible since it's more

	 expensive.  */

      if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))

	{

	  /* Mark the cancellation as "in progress".  */

	  if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,

						    oldval | CANCELING_BITMASK,

						    oldval))

	    goto again;

#ifdef SIGCANCEL

	  /* The cancellation handler will take care of marking the

	     thread as canceled.  */

	  pid_t pid = __getpid ();

	  INTERNAL_SYSCALL_DECL (err);

	  int val = INTERNAL_SYSCALL_CALL (tgkill, err, pid, pd->tid,

					   SIGCANCEL);

	  if (INTERNAL_SYSCALL_ERROR_P (val, err))

	    result = INTERNAL_SYSCALL_ERRNO (val, err);

#else

          /* It should be impossible to get here at all, since

             pthread_setcanceltype should never have allowed

             PTHREAD_CANCEL_ASYNCHRONOUS to be set.  */

          abort ();

#endif

	  break;

	}

	/* A single-threaded process should be able to kill itself, since

	   there is nothing in the POSIX specification that says that it

	   cannot.  So we set multiple_threads to true so that cancellation

	   points get executed.  */

	THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);

#ifndef TLS_MULTIPLE_THREADS_IN_TCB

	__pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;

#endif

    }

  /* Mark the thread as canceled.  This has to be done

     atomically since other bits could be modified as well.  */

  while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,

					       oldval));

  return result;

}

weak_alias (__pthread_cancel, pthread_cancel)

PTHREAD_STATIC_FN_REQUIRE (__pthread_create)