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16adc58e73
Keep __exit_funcs_lock almost all the time and unlock it only to execute callbacks. This fixed two issues. 1. f->func.cxa was modified outside the lock with rare data race like: thread 0: __run_exit_handlers unlock __exit_funcs_lock thread 1: __internal_atexit locks __exit_funcs_lock thread 0: f->flavor = ef_free; thread 1: sees ef_free and use it as new thread 1: new->func.cxa.fn = (void (*) (void *, int)) func; thread 1: new->func.cxa.arg = arg; thread 1: new->flavor = ef_cxa; thread 0: cxafct = f->func.cxa.fn; // it's wrong fn! thread 0: cxafct (f->func.cxa.arg, status); // it's wrong arg! thread 0: goto restart; thread 0: call the same exit_function again as it's ef_cxa 2. Don't unlock in main while loop after *listp = cur->next. If *listp is NULL and __exit_funcs_done is false another thread may fail in __new_exitfn on assert (l != NULL): thread 0: *listp = cur->next; // It can be the last: *listp = NULL. thread 0: __libc_lock_unlock thread 1: __libc_lock_lock in __on_exit thread 1: __new_exitfn thread 1: if (__exit_funcs_done) // false: thread 0 isn't there yet. thread 1: l = *listp thread 1: moves one and crashes on assert (l != NULL); The test needs multiple iterations to consistently fail without the fix. Fixes https://sourceware.org/bugzilla/show_bug.cgi?id=27749 Checked on x86_64-linux-gnu. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
111 lines
2.8 KiB
C
111 lines
2.8 KiB
C
/* Support file for atexit/exit, etc. race tests (BZ #27749).
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Copyright (C) 2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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/* The atexit/exit, at_quick_exit/quick_exit, __cxa_atexit/exit, etc.
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exhibited data race while calling destructors.
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This test registers destructors from the background thread, and checks that
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the same destructor is not called more than once. */
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#include <stdatomic.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <support/check.h>
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#include <support/xthread.h>
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#include <support/xunistd.h>
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#include <sys/wait.h>
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#include <unistd.h>
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static atomic_int registered;
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static atomic_int todo = 100000;
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static void
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atexit_cb (void *arg)
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{
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atomic_fetch_sub (®istered, 1);
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static void *prev;
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if (arg == prev)
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FAIL_EXIT1 ("%s: %p\n", __func__, arg);
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prev = arg;
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while (atomic_load (&todo) > 0 && atomic_load (®istered) < 100)
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;
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}
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int __cxa_atexit (void (*func) (void *), void *arg, void *d);
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static void *
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thread_func (void *arg)
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{
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void *cb_arg = NULL;
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while (atomic_load (&todo) > 0)
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{
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if (atomic_load (®istered) < 10000)
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{
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int n = 10;
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for (int i = 0; i < n; ++i)
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__cxa_atexit (&atexit_cb, ++cb_arg, 0);
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atomic_fetch_add (®istered, n);
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atomic_fetch_sub (&todo, n);
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}
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}
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return NULL;
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}
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_Noreturn static void
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test_and_exit (void)
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{
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pthread_attr_t attr;
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xpthread_attr_init (&attr);
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xpthread_attr_setdetachstate (&attr, 1);
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xpthread_create (&attr, thread_func, NULL);
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xpthread_attr_destroy (&attr);
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while (atomic_load (®istered) == 0)
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;
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exit (0);
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}
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static int
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do_test (void)
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{
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for (int i = 0; i < 20; ++i)
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{
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for (int i = 0; i < 10; ++i)
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if (xfork () == 0)
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test_and_exit ();
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for (int i = 0; i < 10; ++i)
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{
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int status;
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xwaitpid (0, &status, 0);
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if (!WIFEXITED (status))
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FAIL_EXIT1 ("Failed iterations %d", i);
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TEST_COMPARE (WEXITSTATUS (status), 0);
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}
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}
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return 0;
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}
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#define TEST_FUNCTION do_test
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#include <support/test-driver.c>
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