| 1 | /* Single thread optimization, Linux version. |
|---|
| 2 | Copyright (C) 2019-2022 Free Software Foundation, Inc. |
|---|
| 3 | This file is part of the GNU C Library. |
|---|
| 4 | |
|---|
| 5 | The GNU C Library is free software; you can redistribute it and/or |
|---|
| 6 | modify it under the terms of the GNU Lesser General Public |
|---|
| 7 | License as published by the Free Software Foundation; either |
|---|
| 8 | version 2.1 of the License, or (at your option) any later version. |
|---|
| 9 | |
|---|
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
|---|
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
|---|
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
|---|
| 13 | Lesser General Public License for more details. |
|---|
| 14 | |
|---|
| 15 | You should have received a copy of the GNU Lesser General Public |
|---|
| 16 | License along with the GNU C Library; if not, see |
|---|
| 17 | <https://www.gnu.org/licenses/>. */ |
|---|
| 18 | |
|---|
| 19 | #ifndef _SINGLE_THREAD_H |
|---|
| 20 | #define _SINGLE_THREAD_H |
|---|
| 21 | |
|---|
| 22 | /* The default way to check if the process is single thread is by using the |
|---|
| 23 | pthread_t 'multiple_threads' field. However, for some architectures it is |
|---|
| 24 | faster to either use an extra field on TCB or global variables (the TCB |
|---|
| 25 | field is also used on x86 for some single-thread atomic optimizations). |
|---|
| 26 | |
|---|
| 27 | The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single thread |
|---|
| 28 | check to use global variables instead of the pthread_t field. */ |
|---|
| 29 | |
|---|
| 30 | #ifndef __ASSEMBLER__ |
|---|
| 31 | extern int __libc_multiple_threads; |
|---|
| 32 | libc_hidden_proto (__libc_multiple_threads) |
|---|
| 33 | #endif |
|---|
| 34 | |
|---|
| 35 | #if !defined SINGLE_THREAD_BY_GLOBAL || IS_IN (rtld) |
|---|
| 36 | # define SINGLE_THREAD_P \ |
|---|
| 37 | (THREAD_GETMEM (THREAD_SELF, header.multiple_threads) == 0) |
|---|
| 38 | #else |
|---|
| 39 | # define SINGLE_THREAD_P (__libc_multiple_threads == 0) |
|---|
| 40 | #endif |
|---|
| 41 | |
|---|
| 42 | #define RTLD_SINGLE_THREAD_P SINGLE_THREAD_P |
|---|
| 43 | |
|---|
| 44 | #endif /* _SINGLE_THREAD_H */ |
|---|
| 45 | |
|---|
