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/*
* tqueue.h --- task queue handling for Linux.
*
* Mostly based on a proposed bottom-half replacement code written by
* Kai Petzke, wpp@marie.physik.tu-berlin.de.
*
* Modified for use in the Linux kernel by Theodore Ts'o,
* tytso@mit.edu. Any bugs are my fault, not Kai's.
*
* The original comment follows below.
*/
#ifndef _LINUX_TQUEUE_H
#define _LINUX_TQUEUE_H
#include <linux/spinlock.h>
#include <linux/list.h>
#include <asm/bitops.h>
#include <asm/system.h>
/*
* New proposed "bottom half" handlers:
* (C) 1994 Kai Petzke, wpp@marie.physik.tu-berlin.de
*
* Advantages:
* - Bottom halfs are implemented as a linked list. You can have as many
* of them, as you want.
* - No more scanning of a bit field is required upon call of a bottom half.
* - Support for chained bottom half lists. The run_task_queue() function can be
* used as a bottom half handler. This is for example useful for bottom
* halfs, which want to be delayed until the next clock tick.
*
* Notes:
* - Bottom halfs are called in the reverse order that they were linked into
* the list.
*/
struct tq_struct {
struct list_head list; /* linked list of active bh's */
unsigned long sync; /* must be initialized to zero */
void (*routine)(void *); /* function to call */
void *data; /* argument to function */
};
/*
* Emit code to initialise a tq_struct's routine and data pointers
*/
#define PREPARE_TQUEUE(_tq, _routine, _data) \
do { \
(_tq)->routine = _routine; \
(_tq)->data = _data; \
} while (0)
/*
* Emit code to initialise all of a tq_struct
*/
#define INIT_TQUEUE(_tq, _routine, _data) \
do { \
INIT_LIST_HEAD(&(_tq)->list); \
(_tq)->sync = 0; \
PREPARE_TQUEUE((_tq), (_routine), (_data)); \
} while (0)
typedef struct list_head task_queue;
#define DECLARE_TASK_QUEUE(q) LIST_HEAD(q)
#define TQ_ACTIVE(q) (!list_empty(&q))
extern task_queue tq_timer, tq_immediate, tq_disk;
/*
* To implement your own list of active bottom halfs, use the following
* two definitions:
*
* DECLARE_TASK_QUEUE(my_tqueue);
* struct tq_struct my_task = {
* routine: (void (*)(void *)) my_routine,
* data: &my_data
* };
*
* To activate a bottom half on a list, use:
*
* queue_task(&my_task, &my_tqueue);
*
* To later run the queued tasks use
*
* run_task_queue(&my_tqueue);
*
* This allows you to do deferred processing. For example, you could
* have a task queue called tq_timer, which is executed within the timer
* interrupt.
*/
extern spinlock_t tqueue_lock;
/*
* Queue a task on a tq. Return non-zero if it was successfully
* added.
*/
static inline int queue_task(struct tq_struct *bh_pointer, task_queue *bh_list)
{
int ret = 0;
if (!test_and_set_bit(0,&bh_pointer->sync)) {
unsigned long flags;
spin_lock_irqsave(&tqueue_lock, flags);
list_add_tail(&bh_pointer->list, bh_list);
spin_unlock_irqrestore(&tqueue_lock, flags);
ret = 1;
}
return ret;
}
/*
* Call all "bottom halfs" on a given list.
*/
extern void __run_task_queue(task_queue *list);
static inline void run_task_queue(task_queue *list)
{
if (TQ_ACTIVE(*list))
__run_task_queue(list);
}
#endif /* _LINUX_TQUEUE_H */
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