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105 lines
3.4 KiB
C
105 lines
3.4 KiB
C
/* Copyright (C) 2002-2012 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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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <signal.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 <kernel-features.h>
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int
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pthread_cancel (th)
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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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#ifdef SHARED
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pthread_cancel_init ();
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#endif
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int result = 0;
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int oldval;
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int newval;
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do
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{
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again:
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oldval = pd->cancelhandling;
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newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
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/* Avoid doing unnecessary work. The atomic operation can
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potentially be expensive if the bug has to be locked and
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remote cache lines have to be invalidated. */
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if (oldval == newval)
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break;
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/* If the cancellation is handled asynchronously just send a
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signal. We avoid this if possible since it's more
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expensive. */
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if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
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{
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/* Mark the cancellation as "in progress". */
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if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
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oldval | CANCELING_BITMASK,
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oldval))
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goto again;
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/* The cancellation handler will take care of marking the
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thread as canceled. */
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INTERNAL_SYSCALL_DECL (err);
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/* One comment: The PID field in the TCB can temporarily be
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changed (in fork). But this must not affect this code
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here. Since this function would have to be called while
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the thread is executing fork, it would have to happen in
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a signal handler. But this is no allowed, pthread_cancel
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is not guaranteed to be async-safe. */
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int val;
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val = INTERNAL_SYSCALL (tgkill, err, 3,
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THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
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SIGCANCEL);
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if (INTERNAL_SYSCALL_ERROR_P (val, err))
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result = INTERNAL_SYSCALL_ERRNO (val, err);
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break;
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}
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/* A single-threaded process should be able to kill itself, since there is
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nothing in the POSIX specification that says that it cannot. So we set
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multiple_threads to true so that cancellation points get 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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__pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
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#endif
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}
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/* Mark the thread as canceled. This has to be done
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atomically since other bits could be modified as well. */
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while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
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oldval));
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return result;
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}
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PTHREAD_STATIC_FN_REQUIRE (pthread_create)
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