| 1 | /* Single thread optimization, Linux version. |
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| 2 | Copyright (C) 2019-2024 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, see |
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| 17 | <https://www.gnu.org/licenses/>. */ |
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| 18 | |
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| 19 | #ifndef _SINGLE_THREAD_H |
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| 20 | #define _SINGLE_THREAD_H |
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| 21 | |
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| 22 | #ifndef __ASSEMBLER__ |
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| 23 | # include <sys/single_threaded.h> |
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| 24 | #endif |
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| 25 | |
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| 26 | /* The default way to check if the process is single thread is by using the |
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| 27 | pthread_t 'multiple_threads' field. However, for some architectures it is |
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| 28 | faster to either use an extra field on TCB or global variables (the TCB |
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| 29 | field is also used on x86 for some single-thread atomic optimizations). |
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| 30 | |
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| 31 | The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single thread |
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| 32 | check to use global variables instead of the pthread_t field. */ |
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| 33 | |
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| 34 | #if !defined SINGLE_THREAD_BY_GLOBAL || IS_IN (rtld) |
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| 35 | # define SINGLE_THREAD_P \ |
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| 36 | (THREAD_GETMEM (THREAD_SELF, header.multiple_threads) == 0) |
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| 37 | #else |
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| 38 | # define SINGLE_THREAD_P (__libc_single_threaded_internal != 0) |
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| 39 | #endif |
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| 40 | |
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| 41 | #define RTLD_SINGLE_THREAD_P SINGLE_THREAD_P |
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| 42 | |
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| 43 | #endif /* _SINGLE_THREAD_H */ |
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| 44 | |
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