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Diffstat (limited to 'sysdeps/nptl/bits/struct_mutex.h')
| -rw-r--r-- | sysdeps/nptl/bits/struct_mutex.h | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/sysdeps/nptl/bits/struct_mutex.h b/sysdeps/nptl/bits/struct_mutex.h new file mode 100644 index 0000000000..138320b0f3 --- /dev/null +++ b/sysdeps/nptl/bits/struct_mutex.h @@ -0,0 +1,84 @@ +/* Default mutex implementation struct definitions. + 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 _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, 0, __kind, { 0 } +#endif + +#endif |