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Improve semaphore documentation

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Move documentation from semaphore.h to semaphore.c as requested by
Andrew Morton.  Also reformat to kernel-doc style and add some more
notes about the implementation.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
This commit is contained in:
Matthew Wilcox 2008-04-11 15:23:52 -04:00 • committed by Matthew Wilcox
parent b17170b2fa
commit 714493cd54
2 changed files with 70 additions and 48 deletions
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39
include/linux/semaphore.h
View file

@ -4,8 +4,7 @@
*
* Distributed under the terms of the GNU GPL, version 2
*
* Counting semaphores allow up to <n> tasks to acquire the semaphore
* simultaneously.
* Please see kernel/semaphore.c for documentation of these functions
*/
#ifndef __LINUX_SEMAPHORE_H
#define __LINUX_SEMAPHORE_H
@ -13,11 +12,7 @@
#include <linux/list.h>
#include <linux/spinlock.h>
/*
* The spinlock controls access to the other members of the semaphore.
* 'count' represents how many more tasks can acquire this semaphore.
* Tasks waiting for the lock are kept on the wait_list.
*/
/* Please don't access any members of this structure directly */
struct semaphore {
spinlock_t lock;
unsigned int count;
@ -46,41 +41,11 @@ static inline void sema_init(struct semaphore *sem, int val)
#define init_MUTEX(sem) sema_init(sem, 1)
#define init_MUTEX_LOCKED(sem) sema_init(sem, 0)
/*
* Attempt to acquire the semaphore. If another task is already holding the
* semaphore, sleep until the semaphore is released.
*/
extern void down(struct semaphore *sem);
/*
* As down(), except the sleep may be interrupted by a signal. If it is,
* this function will return -EINTR.
*/
extern int __must_check down_interruptible(struct semaphore *sem);
/*
* As down_interruptible(), except the sleep may only be interrupted by
* signals which are fatal to this process.
*/
extern int __must_check down_killable(struct semaphore *sem);
/*
* As down(), except this function will not sleep. It will return 0 if it
* acquired the semaphore and 1 if the semaphore was contended. This
* function may be called from any context, including interrupt and softirq.
*/
extern int __must_check down_trylock(struct semaphore *sem);
/*
* As down(), except this function will return -ETIME if it fails to
* acquire the semaphore within the specified number of jiffies.
*/
extern int __must_check down_timeout(struct semaphore *sem, long jiffies);
/*
* Release the semaphore. Unlike mutexes, up() may be called from any
* context and even by tasks which have never called down().
*/
extern void up(struct semaphore *sem);
#endif /* __LINUX_SEMAPHORE_H */