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eb92f4ef32
Add sem_is_read/write_locked functions to the read/write semaphores, along the same lines of the *_is_locked spinlock functions. The swap token tuning patch uses sem_is_read_locked; sem_is_write_locked is added for completeness. Signed-off-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
/* rwsem-spinlock.h: fallback C implementation
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*
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* Copyright (c) 2001 David Howells (dhowells@redhat.com).
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* - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
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* - Derived also from comments by Linus
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*/
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#ifndef _LINUX_RWSEM_SPINLOCK_H
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#define _LINUX_RWSEM_SPINLOCK_H
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#ifndef _LINUX_RWSEM_H
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#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
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#endif
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#include <linux/spinlock.h>
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#include <linux/list.h>
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#ifdef __KERNEL__
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#include <linux/types.h>
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struct rwsem_waiter;
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/*
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* the rw-semaphore definition
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* - if activity is 0 then there are no active readers or writers
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* - if activity is +ve then that is the number of active readers
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* - if activity is -1 then there is one active writer
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* - if wait_list is not empty, then there are processes waiting for the semaphore
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*/
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struct rw_semaphore {
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__s32 activity;
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spinlock_t wait_lock;
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struct list_head wait_list;
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#if RWSEM_DEBUG
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int debug;
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#endif
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};
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/*
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* initialisation
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*/
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#if RWSEM_DEBUG
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#define __RWSEM_DEBUG_INIT , 0
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#else
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#define __RWSEM_DEBUG_INIT /* */
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#endif
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#define __RWSEM_INITIALIZER(name) \
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{ 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) __RWSEM_DEBUG_INIT }
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#define DECLARE_RWSEM(name) \
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struct rw_semaphore name = __RWSEM_INITIALIZER(name)
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extern void FASTCALL(init_rwsem(struct rw_semaphore *sem));
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extern void FASTCALL(__down_read(struct rw_semaphore *sem));
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extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
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extern void FASTCALL(__down_write(struct rw_semaphore *sem));
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extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
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extern void FASTCALL(__up_read(struct rw_semaphore *sem));
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extern void FASTCALL(__up_write(struct rw_semaphore *sem));
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extern void FASTCALL(__downgrade_write(struct rw_semaphore *sem));
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static inline int rwsem_is_locked(struct rw_semaphore *sem)
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{
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return (sem->activity != 0);
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}
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#endif /* __KERNEL__ */
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#endif /* _LINUX_RWSEM_SPINLOCK_H */
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