diff options
author | Matthew Wilcox <matthew@wil.cx> | 2008-03-08 05:55:58 +0300 |
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committer | Matthew Wilcox <willy@linux.intel.com> | 2008-04-17 18:42:34 +0400 |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /include/asm-s390 | |
parent | e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff) | |
download | linux-64ac24e738823161693bf791f87adc802cf529ff.tar.xz |
Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility. Thanks to Peter Zijlstra for fixing the lockdep
warning. Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/asm-s390')
-rw-r--r-- | include/asm-s390/semaphore.h | 108 |
1 files changed, 1 insertions, 107 deletions
diff --git a/include/asm-s390/semaphore.h b/include/asm-s390/semaphore.h index 0e7001ad8392..d9b2034ed1d2 100644 --- a/include/asm-s390/semaphore.h +++ b/include/asm-s390/semaphore.h @@ -1,107 +1 @@ -/* - * include/asm-s390/semaphore.h - * - * S390 version - * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation - * - * Derived from "include/asm-i386/semaphore.h" - * (C) Copyright 1996 Linus Torvalds - */ - -#ifndef _S390_SEMAPHORE_H -#define _S390_SEMAPHORE_H - -#include <asm/system.h> -#include <asm/atomic.h> -#include <linux/wait.h> -#include <linux/rwsem.h> - -struct semaphore { - /* - * Note that any negative value of count is equivalent to 0, - * but additionally indicates that some process(es) might be - * sleeping on `wait'. - */ - atomic_t count; - wait_queue_head_t wait; -}; - -#define __SEMAPHORE_INITIALIZER(name,count) \ - { ATOMIC_INIT(count), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) } - -#define __DECLARE_SEMAPHORE_GENERIC(name,count) \ - struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) - -#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) - -static inline void sema_init (struct semaphore *sem, int val) -{ - atomic_set(&sem->count, val); - init_waitqueue_head(&sem->wait); -} - -static inline void init_MUTEX (struct semaphore *sem) -{ - sema_init(sem, 1); -} - -static inline void init_MUTEX_LOCKED (struct semaphore *sem) -{ - sema_init(sem, 0); -} - -asmlinkage void __down(struct semaphore * sem); -asmlinkage int __down_interruptible(struct semaphore * sem); -asmlinkage int __down_trylock(struct semaphore * sem); -asmlinkage void __up(struct semaphore * sem); - -static inline void down(struct semaphore * sem) -{ - might_sleep(); - if (atomic_dec_return(&sem->count) < 0) - __down(sem); -} - -static inline int down_interruptible(struct semaphore * sem) -{ - int ret = 0; - - might_sleep(); - if (atomic_dec_return(&sem->count) < 0) - ret = __down_interruptible(sem); - return ret; -} - -static inline int down_trylock(struct semaphore * sem) -{ - int old_val, new_val; - - /* - * This inline assembly atomically implements the equivalent - * to the following C code: - * old_val = sem->count.counter; - * if ((new_val = old_val) > 0) - * sem->count.counter = --new_val; - * In the ppc code this is called atomic_dec_if_positive. - */ - asm volatile( - " l %0,0(%3)\n" - "0: ltr %1,%0\n" - " jle 1f\n" - " ahi %1,-1\n" - " cs %0,%1,0(%3)\n" - " jl 0b\n" - "1:" - : "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter) - : "a" (&sem->count.counter), "m" (sem->count.counter) - : "cc", "memory"); - return old_val <= 0; -} - -static inline void up(struct semaphore * sem) -{ - if (atomic_inc_return(&sem->count) <= 0) - __up(sem); -} - -#endif +#include <linux/semaphore.h> |