glibc/sysdeps/unix/sysv/linux/single-thread.h
Paul Eggert 2b778ceb40 Update copyright dates with scripts/update-copyrights
I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
2021-01-02 12:17:34 -08:00

63 lines
2.3 KiB
C

/* Single thread optimization, Linux version.
Copyright (C) 2019-2021 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/>. */
#ifndef _SINGLE_THREAD_H
#define _SINGLE_THREAD_H
/* The default way to check if the process is single thread is by using the
pthread_t 'multiple_threads' field. However, for some architectures it is
faster to either use an extra field on TCB or global variables (the TCB
field is also used on x86 for some single-thread atomic optimizations).
The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single thread
check to use global variables instead of the pthread_t field. */
#ifdef SINGLE_THREAD_BY_GLOBAL
# if IS_IN (libc)
extern int __libc_multiple_threads;
# define SINGLE_THREAD_P \
__glibc_likely (__libc_multiple_threads == 0)
# elif IS_IN (libpthread)
extern int __pthread_multiple_threads;
# define SINGLE_THREAD_P \
__glibc_likely (__pthread_multiple_threads == 0)
# elif IS_IN (librt)
# define SINGLE_THREAD_P \
__glibc_likely (THREAD_GETMEM (THREAD_SELF, \
header.multiple_threads) == 0)
# else
/* For rtld, et cetera. */
# define SINGLE_THREAD_P (1)
# endif
#else /* SINGLE_THREAD_BY_GLOBAL */
# if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
# define SINGLE_THREAD_P \
__glibc_likely (THREAD_GETMEM (THREAD_SELF, \
header.multiple_threads) == 0)
# else
/* For rtld, et cetera. */
# define SINGLE_THREAD_P (1)
# endif
#endif /* SINGLE_THREAD_BY_GLOBAL */
#define RTLD_SINGLE_THREAD_P \
__glibc_likely (THREAD_GETMEM (THREAD_SELF, \
header.multiple_threads) == 0)
#endif /* _SINGLE_THREAD_H */