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Generic semaphore implementation

Browse source 
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 <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
This commit is contained in:
Matthew Wilcox 2008-03-07 21:55:58 -05:00 • committed by Matthew Wilcox
commit 64ac24e738
113 changed files with 314 additions and 7679 deletions
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100
include/asm-ia64/semaphore.h
View file

@ -1,99 +1 @@
#ifndef _ASM_IA64_SEMAPHORE_H
#define _ASM_IA64_SEMAPHORE_H
/*
* Copyright (C) 1998-2000 Hewlett-Packard Co
* Copyright (C) 1998-2000 David Mosberger-Tang <davidm@hpl.hp.com>
*/
#include <linux/wait.h>
#include <linux/rwsem.h>
#include <asm/atomic.h>
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);
}
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);
}
extern void __down (struct semaphore * sem);
extern int __down_interruptible (struct semaphore * sem);
extern int __down_trylock (struct semaphore * sem);
extern void __up (struct semaphore * sem);
/*
* Atomically decrement the semaphore's count. If it goes negative,
* block the calling thread in the TASK_UNINTERRUPTIBLE state.
*/
static inline void
down (struct semaphore *sem)
{
might_sleep();
if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
__down(sem);
}
/*
* Atomically decrement the semaphore's count. If it goes negative,
* block the calling thread in the TASK_INTERRUPTIBLE state.
*/
static inline int
down_interruptible (struct semaphore * sem)
{
int ret = 0;
might_sleep();
if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
ret = __down_interruptible(sem);
return ret;
}
static inline int
down_trylock (struct semaphore *sem)
{
int ret = 0;
if (ia64_fetchadd(-1, &sem->count.counter, acq) < 1)
ret = __down_trylock(sem);
return ret;
}
static inline void
up (struct semaphore * sem)
{
if (ia64_fetchadd(1, &sem->count.counter, rel) <= -1)
__up(sem);
}
#endif /* _ASM_IA64_SEMAPHORE_H */
#include <linux/semaphore.h>