From 64ac24e738823161693bf791f87adc802cf529ff Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 7 Mar 2008 21:55:58 -0500 Subject: 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 Acked-by: Ingo Molnar --- include/asm-sh/semaphore-helper.h | 89 ----------------------------- include/asm-sh/semaphore.h | 116 +------------------------------------- 2 files changed, 1 insertion(+), 204 deletions(-) delete mode 100644 include/asm-sh/semaphore-helper.h (limited to 'include/asm-sh') diff --git a/include/asm-sh/semaphore-helper.h b/include/asm-sh/semaphore-helper.h deleted file mode 100644 index bd8230c369ca..000000000000 --- a/include/asm-sh/semaphore-helper.h +++ /dev/null @@ -1,89 +0,0 @@ -#ifndef __ASM_SH_SEMAPHORE_HELPER_H -#define __ASM_SH_SEMAPHORE_HELPER_H - -/* - * SMP- and interrupt-safe semaphores helper functions. - * - * (C) Copyright 1996 Linus Torvalds - * (C) Copyright 1999 Andrea Arcangeli - */ - -/* - * These two _must_ execute atomically wrt each other. - * - * This is trivially done with load_locked/store_cond, - * which we have. Let the rest of the losers suck eggs. - */ -static __inline__ void wake_one_more(struct semaphore * sem) -{ - atomic_inc((atomic_t *)&sem->sleepers); -} - -static __inline__ int waking_non_zero(struct semaphore *sem) -{ - unsigned long flags; - int ret = 0; - - spin_lock_irqsave(&semaphore_wake_lock, flags); - if (sem->sleepers > 0) { - sem->sleepers--; - ret = 1; - } - spin_unlock_irqrestore(&semaphore_wake_lock, flags); - return ret; -} - -/* - * waking_non_zero_interruptible: - * 1 got the lock - * 0 go to sleep - * -EINTR interrupted - * - * We must undo the sem->count down_interruptible() increment while we are - * protected by the spinlock in order to make atomic this atomic_inc() with the - * atomic_read() in wake_one_more(), otherwise we can race. -arca - */ -static __inline__ int waking_non_zero_interruptible(struct semaphore *sem, - struct task_struct *tsk) -{ - unsigned long flags; - int ret = 0; - - spin_lock_irqsave(&semaphore_wake_lock, flags); - if (sem->sleepers > 0) { - sem->sleepers--; - ret = 1; - } else if (signal_pending(tsk)) { - atomic_inc(&sem->count); - ret = -EINTR; - } - spin_unlock_irqrestore(&semaphore_wake_lock, flags); - return ret; -} - -/* - * waking_non_zero_trylock: - * 1 failed to lock - * 0 got the lock - * - * We must undo the sem->count down_trylock() increment while we are - * protected by the spinlock in order to make atomic this atomic_inc() with the - * atomic_read() in wake_one_more(), otherwise we can race. -arca - */ -static __inline__ int waking_non_zero_trylock(struct semaphore *sem) -{ - unsigned long flags; - int ret = 1; - - spin_lock_irqsave(&semaphore_wake_lock, flags); - if (sem->sleepers <= 0) - atomic_inc(&sem->count); - else { - sem->sleepers--; - ret = 0; - } - spin_unlock_irqrestore(&semaphore_wake_lock, flags); - return ret; -} - -#endif /* __ASM_SH_SEMAPHORE_HELPER_H */ diff --git a/include/asm-sh/semaphore.h b/include/asm-sh/semaphore.h index 9e5a37c4dce2..d9b2034ed1d2 100644 --- a/include/asm-sh/semaphore.h +++ b/include/asm-sh/semaphore.h @@ -1,115 +1 @@ -#ifndef __ASM_SH_SEMAPHORE_H -#define __ASM_SH_SEMAPHORE_H - -#include - -#ifdef __KERNEL__ -/* - * SMP- and interrupt-safe semaphores. - * - * (C) Copyright 1996 Linus Torvalds - * - * SuperH verison by Niibe Yutaka - * (Currently no asm implementation but generic C code...) - */ - -#include -#include -#include - -#include -#include - -struct semaphore { - atomic_t count; - int sleepers; - wait_queue_head_t wait; -}; - -#define __SEMAPHORE_INITIALIZER(name, n) \ -{ \ - .count = ATOMIC_INIT(n), \ - .sleepers = 0, \ - .wait = __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) -{ -/* - * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); - * - * i'd rather use the more flexible initialization above, but sadly - * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well. - */ - atomic_set(&sem->count, val); - sem->sleepers = 0; - 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); -} - -#if 0 -asmlinkage void __down_failed(void /* special register calling convention */); -asmlinkage int __down_failed_interruptible(void /* params in registers */); -asmlinkage int __down_failed_trylock(void /* params in registers */); -asmlinkage void __up_wakeup(void /* special register calling convention */); -#endif - -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); - -extern spinlock_t semaphore_wake_lock; - -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 ret = 0; - - if (atomic_dec_return(&sem->count) < 0) - ret = __down_trylock(sem); - return ret; -} - -/* - * Note! This is subtle. We jump to wake people up only if - * the semaphore was negative (== somebody was waiting on it). - */ -static inline void up(struct semaphore * sem) -{ - if (atomic_inc_return(&sem->count) <= 0) - __up(sem); -} - -#endif -#endif /* __ASM_SH_SEMAPHORE_H */ +#include -- cgit v1.2.3-59-g8ed1b