glibc/elf/tst-single_threaded.c
Florian Weimer 706ad1e7af Add the __libc_single_threaded variable
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>
2020-07-06 11:15:58 +02:00

71 lines
2.3 KiB
C

/* Test support for single-thread optimizations. No threads.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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
<https://www.gnu.org/licenses/>. */
#include <stddef.h>
#include <stdio.h>
#include <support/check.h>
#include <support/namespace.h>
#include <support/xdlfcn.h>
#include <sys/single_threaded.h>
/* Defined in tst-single-threaded-mod1.so. */
extern _Bool single_threaded_1 (void);
/* Initialized via dlsym. */
_Bool (*single_threaded_2) (void);
_Bool (*single_threaded_3) (void);
static void
subprocess (void *closure)
{
TEST_VERIFY (__libc_single_threaded);
TEST_VERIFY (single_threaded_1 ());
if (single_threaded_2 != NULL)
TEST_VERIFY (single_threaded_2 ());
if (single_threaded_3 != NULL)
TEST_VERIFY (!single_threaded_3 ());
}
static int
do_test (void)
{
TEST_VERIFY (__libc_single_threaded);
TEST_VERIFY (single_threaded_1 ());
support_isolate_in_subprocess (subprocess, NULL);
void *handle_mod2 = xdlopen ("tst-single_threaded-mod2.so", RTLD_LAZY);
single_threaded_2 = xdlsym (handle_mod2, "single_threaded_2");
TEST_VERIFY (single_threaded_2 ());
support_isolate_in_subprocess (subprocess, NULL);
/* The current implementation treats the inner namespace as
multi-threaded. */
void *handle_mod3 = dlmopen (LM_ID_NEWLM, "tst-single_threaded-mod3.so",
RTLD_LAZY);
single_threaded_3 = xdlsym (handle_mod3, "single_threaded_3");
TEST_VERIFY (!single_threaded_3 ());
support_isolate_in_subprocess (subprocess, NULL);
xdlclose (handle_mod3);
xdlclose (handle_mod2);
return 0;
}
#include <support/test-driver.c>