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The variable is placed in libc.so, and it can be true only in an outer libc, not libcs loaded via dlmopen or static dlopen. Since thread creation from inner namespaces does not work, pthread_create can update __libc_single_threaded directly. Using __libc_early_init and its initial flag, implementation of this variable is very straightforward. A future version may reset the flag during fork (but not in an inner namespace), or after joining all threads except one. Reviewed-by: DJ Delorie <dj@redhat.com>
58 lines
2.0 KiB
C
58 lines
2.0 KiB
C
/* Test support for single-thread optimizations. No threads, static dlopen.
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Copyright (C) 2020 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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/* In a static dlopen scenario, the single-threaded optimization is
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not possible because their is no globally shared dynamic linker
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across all namespaces. */
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#include <stddef.h>
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#include <support/check.h>
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#include <support/xdlfcn.h>
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#include <sys/single_threaded.h>
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static int
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do_test (void)
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{
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TEST_VERIFY (__libc_single_threaded);
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/* Defined in tst-single-threaded-mod1.o. */
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extern _Bool single_threaded_1 (void);
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TEST_VERIFY (single_threaded_1 ());
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/* A failed dlopen does not change the multi-threaded status. */
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TEST_VERIFY (dlopen ("tst-single_threaded-does-not-exist.so", RTLD_LAZY)
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== NULL);
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TEST_VERIFY (__libc_single_threaded);
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TEST_VERIFY (single_threaded_1 ());
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/* And neither does a successful dlopen for outer (static) libc. */
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void *handle_mod2 = xdlopen ("tst-single_threaded-mod2.so", RTLD_LAZY);
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_Bool (*single_threaded_2) (void)
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= xdlsym (handle_mod2, "single_threaded_2");
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TEST_VERIFY (__libc_single_threaded);
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TEST_VERIFY (single_threaded_1 ());
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/* The inner libc always assumes multi-threaded use. */
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TEST_VERIFY (!single_threaded_2 ());
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xdlclose (handle_mod2);
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return 0;
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}
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#include <support/test-driver.c>
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