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/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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>
#include <unwind-link.h>
#include <stdio.h>
#include <gnu/lib-names.h>
#include <sys/single_threaded.h>
/* For asynchronous cancellation we use a signal. */
static void
sigcancel_handler (int sig, siginfo_t *si, void *ctx)
{
/* Safety check. It would be possible to call this function for
other signals and send a signal from another process. This is not
correct and might even be a security problem. Try to catch as
many incorrect invocations as possible. */
if (sig != SIGCANCEL
|| si->si_pid != __getpid()
|| si->si_code != SI_TKILL)
return;
struct pthread *self = THREAD_SELF;
int ch = atomic_load_relaxed (&self->cancelhandling);
/* Cancelation not enabled, not cancelled, or already exitting. */
if (self->cancelstate == PTHREAD_CANCEL_DISABLE
|| (ch & CANCELED_BITMASK) == 0
|| (ch & EXITING_BITMASK) != 0)
return;
/* Set the return value. */
THREAD_SETMEM (self, result, PTHREAD_CANCELED);
/* Make sure asynchronous cancellation is still enabled. */
if (self->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)
__do_cancel ();
}
int
__pthread_cancel (pthread_t th)
{
volatile struct pthread *pd = (volatile struct pthread *) th;
if (pd->tid == 0)
/* The thread has already exited on the kernel side. Its outcome
(regular exit, other cancelation) has already been
determined. */
return 0;
static int init_sigcancel = 0;
if (atomic_load_relaxed (&init_sigcancel) == 0)
{
struct sigaction sa;
sa.sa_sigaction = sigcancel_handler;
/* The signal handle should be non-interruptible to avoid the risk of
spurious EINTR caused by SIGCANCEL sent to process or if
pthread_cancel() is called while cancellation is disabled in the
target thread. */
sa.sa_flags = SA_SIGINFO | SA_RESTART;
__sigemptyset (&sa.sa_mask);
__libc_sigaction (SIGCANCEL, &sa, NULL);
atomic_store_relaxed (&init_sigcancel, 1);
}
#ifdef SHARED
/* Trigger an error if libgcc_s cannot be loaded. */
{
struct unwind_link *unwind_link = __libc_unwind_link_get ();
if (unwind_link == NULL)
__libc_fatal (LIBGCC_S_SO
" must be installed for pthread_cancel to work\n");
}
#endif
int oldch = atomic_fetch_or_acquire (&pd->cancelhandling, CANCELED_BITMASK);
if ((oldch & CANCELED_BITMASK) != 0)
return 0;
if (pd == THREAD_SELF)
{
/* 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
__libc_multiple_threads = 1;
#endif
THREAD_SETMEM (pd, result, PTHREAD_CANCELED);
if (pd->cancelstate == PTHREAD_CANCEL_ENABLE
&& pd->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)
__do_cancel ();
return 0;
}
return __pthread_kill_internal (th, SIGCANCEL);
}
versioned_symbol (libc, __pthread_cancel, pthread_cancel, GLIBC_2_34);
#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
compat_symbol (libpthread, __pthread_cancel, pthread_cancel, GLIBC_2_0);
#endif
/* Ensure that the unwinder is always linked in (the __pthread_unwind
reference from __do_cancel is weak). Use ___pthread_unwind_next
(three underscores) to produce a strong reference to the same
file. */
PTHREAD_STATIC_FN_REQUIRE (___pthread_unwind_next)
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