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/* Copyright (C) 2002-2020 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
<https://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;
/* The cancellation handler will take care of marking the
thread as canceled. */
pid_t pid = __getpid ();
int val = INTERNAL_SYSCALL_CALL (tgkill, pid, pd->tid,
SIGCANCEL);
if (INTERNAL_SYSCALL_ERROR_P (val))
result = INTERNAL_SYSCALL_ERRNO (val);
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)
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