85 lines
3.0 KiB
C
85 lines
3.0 KiB
C
|
/* Default mutex implementation struct definitions.
|
||
|
|
Copyright (C) 2019-2022 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 _THREAD_MUTEX_INTERNAL_H
|
||
|
|
#define _THREAD_MUTEX_INTERNAL_H 1
|
||
|
|
|
||
|
|
/* Generic struct for both POSIX and C11 mutexes. New ports are expected
|
||
|
|
to use the default layout, however architecture can redefine it to
|
||
|
|
add arch-specific extension (such as lock-elision). The struct have
|
||
|
|
a size of 32 bytes on LP32 and 40 bytes on LP64 architectures. */
|
||
|
|
|
||
|
|
struct __pthread_mutex_s
|
||
|
|
{
|
||
|
|
int __lock __LOCK_ALIGNMENT;
|
||
|
|
unsigned int __count;
|
||
|
|
int __owner;
|
||
|
|
#if __WORDSIZE == 64
|
||
|
|
unsigned int __nusers;
|
||
|
|
#endif
|
||
|
|
/* KIND must stay at this position in the structure to maintain
|
||
|
|
binary compatibility with static initializers.
|
||
|
|
|
||
|
|
Concurrency notes:
|
||
|
|
The __kind of a mutex is initialized either by the static
|
||
|
|
PTHREAD_MUTEX_INITIALIZER or by a call to pthread_mutex_init.
|
||
|
|
|
||
|
|
After a mutex has been initialized, the __kind of a mutex is usually not
|
||
|
|
changed. BUT it can be set to -1 in pthread_mutex_destroy or elision can
|
||
|
|
be enabled. This is done concurrently in the pthread_mutex_*lock
|
||
|
|
functions by using the macro FORCE_ELISION. This macro is only defined
|
||
|
|
for architectures which supports lock elision.
|
||
|
|
|
||
|
|
For elision, there are the flags PTHREAD_MUTEX_ELISION_NP and
|
||
|
|
PTHREAD_MUTEX_NO_ELISION_NP which can be set in addition to the already
|
||
|
|
set type of a mutex. Before a mutex is initialized, only
|
||
|
|
PTHREAD_MUTEX_NO_ELISION_NP can be set with pthread_mutexattr_settype.
|
||
|
|
|
||
|
|
After a mutex has been initialized, the functions pthread_mutex_*lock can
|
||
|
|
enable elision - if the mutex-type and the machine supports it - by
|
||
|
|
setting the flag PTHREAD_MUTEX_ELISION_NP. This is done concurrently.
|
||
|
|
Afterwards the lock / unlock functions are using specific elision
|
||
|
|
code-paths. */
|
||
|
|
int __kind;
|
||
|
|
#if __WORDSIZE != 64
|
||
|
|
unsigned int __nusers;
|
||
|
|
#endif
|
||
|
|
#if __WORDSIZE == 64
|
||
|
|
int __spins;
|
||
|
|
__pthread_list_t __list;
|
||
|
|
# define __PTHREAD_MUTEX_HAVE_PREV 1
|
||
|
|
#else
|
||
|
|
__extension__ union
|
||
|
|
{
|
||
|
|
int __spins;
|
||
|
|
__pthread_slist_t __list;
|
||
|
|
};
|
||
|
|
# define __PTHREAD_MUTEX_HAVE_PREV 0
|
||
|
|
#endif
|
||
|
|
};
|
||
|
|
|
||
|
|
#if __PTHREAD_MUTEX_HAVE_PREV == 1
|
||
|
|
# define __PTHREAD_MUTEX_INITIALIZER(__kind) \
|
||
|
|
0, 0, 0, 0, __kind, 0, { 0, 0 }
|
||
|
|
#else
|
||
|
|
# define __PTHREAD_MUTEX_INITIALIZER(__kind) \
|
||
|
|
0, 0, 0, __kind, 0, { 0 }
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#endif
|