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/* Copyright (C) 2002-2014 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 "pthreadP.h"
#include "atomic.h"
#include <sysdep.h>
#include <kernel-features.h>
int
pthread_cancel (th)
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;
/* The cancellation handler will take care of marking the
thread as canceled. */
INTERNAL_SYSCALL_DECL (err);
/* One comment: The PID field in the TCB can temporarily be
changed (in fork). But this must not affect this code
here. Since this function would have to be called while
the thread is executing fork, it would have to happen in
a signal handler. But this is no allowed, pthread_cancel
is not guaranteed to be async-safe. */
int val;
val = INTERNAL_SYSCALL (tgkill, err, 3,
THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
SIGCANCEL);
if (INTERNAL_SYSCALL_ERROR_P (val, err))
result = INTERNAL_SYSCALL_ERRNO (val, err);
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;
}
PTHREAD_STATIC_FN_REQUIRE (pthread_create)
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