1 /*
2 * tqueue.h --- task queue handling for Linux.
3 *
4 * Mostly based on a proposed bottom-half replacement code written by
5 * Kai Petzke, wpp@marie.physik.tu-berlin.de.
6 *
7 * Modified for use in the Linux kernel by Theodore Ts'o,
8 * tytso@mit.edu. Any bugs are my fault, not Kai's.
9 *
10 * The original comment follows below.
11 */
12
13 #ifndef _LINUX_TQUEUE_H
14 #define _LINUX_TQUEUE_H
15
16 #include <linux/spinlock.h>
17 #include <linux/list.h>
18 #include <asm/bitops.h>
19 #include <asm/system.h>
20
21 /*
22 * New proposed "bottom half" handlers:
23 * (C) 1994 Kai Petzke, wpp@marie.physik.tu-berlin.de
24 *
25 * Advantages:
26 * - Bottom halfs are implemented as a linked list. You can have as many
27 * of them, as you want.
28 * - No more scanning of a bit field is required upon call of a bottom half.
29 * - Support for chained bottom half lists. The run_task_queue() function can be
30 * used as a bottom half handler. This is for example useful for bottom
31 * halfs, which want to be delayed until the next clock tick.
32 *
33 * Notes:
34 * - Bottom halfs are called in the reverse order that they were linked into
35 * the list.
36 */
37
38 struct tq_struct {
39 struct list_head list; /* linked list of active bh's */
40 unsigned long sync; /* must be initialized to zero */
41 void (*routine)(void *); /* function to call */
42 void *data; /* argument to function */
43 };
44
45 typedef struct list_head task_queue;
46
47 #define DECLARE_TASK_QUEUE(q) LIST_HEAD(q)
48 #define TQ_ACTIVE(q) (!list_empty(&q))
49
50 extern task_queue tq_timer, tq_immediate, tq_disk;
51
52 /*
53 * To implement your own list of active bottom halfs, use the following
54 * two definitions:
55 *
56 * DECLARE_TASK_QUEUE(my_tqueue);
57 * struct tq_struct my_task = {
58 * routine: (void (*)(void *)) my_routine,
59 * data: &my_data
60 * };
61 *
62 * To activate a bottom half on a list, use:
63 *
64 * queue_task(&my_task, &my_tqueue);
65 *
66 * To later run the queued tasks use
67 *
68 * run_task_queue(&my_tqueue);
69 *
70 * This allows you to do deferred processing. For example, you could
71 * have a task queue called tq_timer, which is executed within the timer
72 * interrupt.
73 */
74
75 extern spinlock_t tqueue_lock;
76
77 /*
78 * Queue a task on a tq. Return non-zero if it was successfully
79 * added.
80 */
81 static inline int queue_task(struct tq_struct *bh_pointer, task_queue *bh_list)
82 {
83 int ret = 0;
84 if (!test_and_set_bit(0,&bh_pointer->sync)) {
85 unsigned long flags;
86 spin_lock_irqsave(&tqueue_lock, flags);
87 list_add_tail(&bh_pointer->list, bh_list);
88 spin_unlock_irqrestore(&tqueue_lock, flags);
89 ret = 1;
90 }
91 return ret;
92 }
93
94 /*
95 * Call all "bottom halfs" on a given list.
96 */
97
98 extern void __run_task_queue(task_queue *list);
99
100 static inline void run_task_queue(task_queue *list)
101 {
102 if (TQ_ACTIVE(*list))
103 __run_task_queue(list);
104 }
105
106 #endif /* _LINUX_TQUEUE_H */
107
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