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glibc/nptl/pthread_cancel.c
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/* Copyright (C) 2002-2016 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 <stdlib.h> | |
#include "pthreadP.h" | |
#include <atomic.h> | |
#include <sysdep.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; | |
#ifdef SIGCANCEL | |
/* 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); | |
#else | |
/* It should be impossible to get here at all, since | |
pthread_setcanceltype should never have allowed | |
PTHREAD_CANCEL_ASYNCHRONOUS to be set. */ | |
abort (); | |
#endif | |
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) |