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63 lines
2.3 KiB
C
63 lines
2.3 KiB
C
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/* Single thread optimization, Linux version.
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Copyright (C) 2019 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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<http://www.gnu.org/licenses/>. */
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#ifndef _SINGLE_THREAD_H
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#define _SINGLE_THREAD_H
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/* The default way to check if the process is single thread is by using the
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pthread_t 'multiple_threads' field. However, for some architectures it is
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faster to either use an extra field on TCB or global variables (the TCB
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field is also used on x86 for some single-thread atomic optimizations).
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The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single thread
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check to use global variables instead of the pthread_t field. */
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#ifdef SINGLE_THREAD_BY_GLOBAL
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# if IS_IN (libc)
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extern int __libc_multiple_threads;
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# define SINGLE_THREAD_P \
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__glibc_likely (__libc_multiple_threads == 0)
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# elif IS_IN (libpthread)
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extern int __pthread_multiple_threads;
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# define SINGLE_THREAD_P \
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__glibc_likely (__pthread_multiple_threads == 0)
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# elif IS_IN (librt)
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# define SINGLE_THREAD_P \
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__glibc_likely (THREAD_GETMEM (THREAD_SELF, \
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header.multiple_threads) == 0)
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# else
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/* For rtld, et cetera. */
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# define SINGLE_THREAD_P (1)
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# endif
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#else /* SINGLE_THREAD_BY_GLOBAL */
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# if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
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# define SINGLE_THREAD_P \
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__glibc_likely (THREAD_GETMEM (THREAD_SELF, \
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header.multiple_threads) == 0)
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# else
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/* For rtld, et cetera. */
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# define SINGLE_THREAD_P (1)
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# endif
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#endif /* SINGLE_THREAD_BY_GLOBAL */
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#define RTLD_SINGLE_THREAD_P \
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__glibc_likely (THREAD_GETMEM (THREAD_SELF, \
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header.multiple_threads) == 0)
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#endif /* _SINGLE_THREAD_H */
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