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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 <asm/bitops.h>
#include <asm/system.h>
#include <asm/spinlock.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.
*
* Problems:
* - The queue_task_irq() inline function is only atomic with respect to itself.
* Problems can occur, when queue_task_irq() is called from a normal system
* call, and an interrupt comes in. No problems occur, when queue_task_irq()
* is called from an interrupt or bottom half, and interrupted, as run_task_queue()
* will not be executed/continued before the last interrupt returns. If in
* doubt, use queue_task(), not queue_task_irq().
* - Bottom halfs are called in the reverse order that they were linked into
* the list.
*/
struct tq_struct {
struct tq_struct *next; /* 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 */
};
typedef struct tq_struct * task_queue;
#define DECLARE_TASK_QUEUE(q) task_queue q = NULL
#define TQ_ACTIVE(q) ((q) != NULL)
extern task_queue tq_timer, tq_immediate, tq_scheduler, tq_disk;
/*
* To implement your own list of active bottom halfs, use the following
* two definitions:
*
* struct tq_struct *my_bh = NULL;
* struct tq_struct run_my_bh = {
* 0, 0, (void (*)(void *)) run_task_queue, &my_bh
* };
*
* To activate a bottom half on your list, use:
*
* queue_task(tq_pointer, &my_bh);
*
* To run the bottom halfs on your list put them on the immediate list by:
*
* queue_task(&run_my_bh, &tq_immediate);
*
* This allows you to do deferred procession. For example, you could
* have a bottom half list tq_timer, which is marked active by the timer
* interrupt.
*/
extern spinlock_t tqueue_lock;
/*
* Queue a task on a tq. Return non-zero if it was successfully
* added.
*/
extern __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);
bh_pointer->next = *bh_list;
*bh_list = bh_pointer;
spin_unlock_irqrestore(&tqueue_lock, flags);
ret = 1;
}
return ret;
}
/*
* Call all "bottom halfs" on a given list.
*/
extern __inline__ void run_task_queue(task_queue *list)
{
if (*list) {
unsigned long flags;
struct tq_struct *p;
spin_lock_irqsave(&tqueue_lock, flags);
p = *list;
*list = NULL;
spin_unlock_irqrestore(&tqueue_lock, flags);
while (p) {
void *arg;
void (*f) (void *);
struct tq_struct *save_p;
arg = p -> data;
f = p -> routine;
save_p = p;
p = p -> next;
mb();
save_p -> sync = 0;
(*f)(arg);
}
}
}
#endif /* _LINUX_TQUEUE_H */
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