diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/single-thread.h')
| -rw-r--r-- | sysdeps/unix/sysv/linux/single-thread.h | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/single-thread.h b/sysdeps/unix/sysv/linux/single-thread.h new file mode 100644 index 0000000000..2c972f37b3 --- /dev/null +++ b/sysdeps/unix/sysv/linux/single-thread.h @@ -0,0 +1,62 @@ +/* Single thread optimization, Linux version. + Copyright (C) 2019 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 + <http://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 */ |