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a6c813d0ad
It consolidates the tgkill call and it is the first step of making
pthread_cancel async-signal-safe. It also fix a possible issue
where the 'struct pthread' tid is not read atomically, which might
send an invalid cancellation signal (similar to what
db988e50a8 fixed for pthread_join).
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
126 lines
4.1 KiB
C
126 lines
4.1 KiB
C
/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <signal.h>
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#include <stdlib.h>
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#include "pthreadP.h"
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#include <atomic.h>
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#include <sysdep.h>
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#include <unistd.h>
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#include <unwind-link.h>
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#include <stdio.h>
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#include <gnu/lib-names.h>
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#include <sys/single_threaded.h>
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/* For asynchronous cancellation we use a signal. */
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static void
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sigcancel_handler (int sig, siginfo_t *si, void *ctx)
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{
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/* Safety check. It would be possible to call this function for
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other signals and send a signal from another process. This is not
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correct and might even be a security problem. Try to catch as
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many incorrect invocations as possible. */
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if (sig != SIGCANCEL
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|| si->si_pid != __getpid()
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|| si->si_code != SI_TKILL)
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return;
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struct pthread *self = THREAD_SELF;
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int ch = atomic_load_relaxed (&self->cancelhandling);
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/* Cancelation not enabled, not cancelled, or already exitting. */
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if (self->cancelstate == PTHREAD_CANCEL_DISABLE
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|| (ch & CANCELED_BITMASK) == 0
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|| (ch & EXITING_BITMASK) != 0)
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return;
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/* Set the return value. */
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THREAD_SETMEM (self, result, PTHREAD_CANCELED);
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/* Make sure asynchronous cancellation is still enabled. */
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if (self->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)
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__do_cancel ();
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}
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int
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__pthread_cancel (pthread_t th)
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{
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volatile struct pthread *pd = (volatile struct pthread *) th;
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/* Make sure the descriptor is valid. */
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if (INVALID_TD_P (pd))
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/* Not a valid thread handle. */
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return ESRCH;
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static int init_sigcancel = 0;
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if (atomic_load_relaxed (&init_sigcancel) == 0)
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{
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struct sigaction sa;
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sa.sa_sigaction = sigcancel_handler;
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sa.sa_flags = SA_SIGINFO;
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__sigemptyset (&sa.sa_mask);
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__libc_sigaction (SIGCANCEL, &sa, NULL);
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atomic_store_relaxed (&init_sigcancel, 1);
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}
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#ifdef SHARED
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/* Trigger an error if libgcc_s cannot be loaded. */
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{
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struct unwind_link *unwind_link = __libc_unwind_link_get ();
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if (unwind_link == NULL)
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__libc_fatal (LIBGCC_S_SO
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" must be installed for pthread_cancel to work\n");
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}
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#endif
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int oldch = atomic_fetch_or_acquire (&pd->cancelhandling, CANCELED_BITMASK);
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if ((oldch & CANCELED_BITMASK) != 0)
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return 0;
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if (pd == THREAD_SELF)
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{
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/* A single-threaded process should be able to kill itself, since there
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is nothing in the POSIX specification that says that it cannot. So
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we set multiple_threads to true so that cancellation points get
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executed. */
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THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
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#ifndef TLS_MULTIPLE_THREADS_IN_TCB
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__libc_multiple_threads = 1;
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#endif
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THREAD_SETMEM (pd, result, PTHREAD_CANCELED);
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if (pd->cancelstate == PTHREAD_CANCEL_ENABLE
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&& pd->canceltype == PTHREAD_CANCEL_ASYNCHRONOUS)
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__do_cancel ();
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return 0;
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}
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return __pthread_kill_internal (th, SIGCANCEL);
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}
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versioned_symbol (libc, __pthread_cancel, pthread_cancel, GLIBC_2_34);
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#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
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compat_symbol (libpthread, __pthread_cancel, pthread_cancel, GLIBC_2_0);
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#endif
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/* Ensure that the unwinder is always linked in (the __pthread_unwind
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reference from __do_cancel is weak). Use ___pthread_unwind_next
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(three underscores) to produce a strong reference to the same
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file. */
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PTHREAD_STATIC_FN_REQUIRE (___pthread_unwind_next)
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