1/* Single-thread optimization definitions. Linux version.
2 Copyright (C) 2017-2019 Free Software Foundation, Inc.
3
4 This file is part of the GNU C Library.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20#include <sysdep.h>
21#include <tls.h>
22#include <nptl/pthreadP.h>
23
24/* The default way to check if the process is single thread is by using the
25 pthread_t 'multiple_threads' field. However for some architectures it
26 is faster to either use an extra field on TCB or global varibles
27 (the TCB field is also used on x86 for some single-thread atomic
28 optimizations).
29
30 The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single
31 thread check to use global variables instead of the pthread_t
32 field. */
33
34#ifdef SINGLE_THREAD_BY_GLOBAL
35# if IS_IN (libc)
36extern int __libc_multiple_threads;
37# define SINGLE_THREAD_P \
38 __glibc_likely (__libc_multiple_threads == 0)
39# elif IS_IN (libpthread)
40extern int __pthread_multiple_threads;
41# define SINGLE_THREAD_P \
42 __glibc_likely (__pthread_multiple_threads == 0)
43# elif IS_IN (librt)
44# define SINGLE_THREAD_P \
45 __glibc_likely (THREAD_GETMEM (THREAD_SELF, \
46 header.multiple_threads) == 0)
47# else
48/* For rtld, et cetera. */
49# define SINGLE_THREAD_P (1)
50# endif
51#else /* SINGLE_THREAD_BY_GLOBAL */
52# if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
53# define SINGLE_THREAD_P \
54 __glibc_likely (THREAD_GETMEM (THREAD_SELF, \
55 header.multiple_threads) == 0)
56# else
57/* For rtld, et cetera. */
58# define SINGLE_THREAD_P (1)
59# endif
60#endif /* SINGLE_THREAD_BY_GLOBAL */
61
62#define RTLD_SINGLE_THREAD_P \
63 __glibc_likely (THREAD_GETMEM (THREAD_SELF, \
64 header.multiple_threads) == 0)
65