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 /*
46 * Emit code to initialise a tq_struct's routine and data pointers
47 */
48 #define PREPARE_TQUEUE(_tq, _routine, _data) \
49 do { \
50 (_tq)->routine = _routine; \
51 (_tq)->data = _data; \
52 } while (0)
53
54 /*
55 * Emit code to initialise all of a tq_struct
56 */
57 #define INIT_TQUEUE(_tq, _routine, _data) \
58 do { \
59 INIT_LIST_HEAD(&(_tq)->list); \
60 (_tq)->sync = 0; \
61 PREPARE_TQUEUE((_tq), (_routine), (_data)); \
62 } while (0)
63
64 typedef struct list_head task_queue;
65
66 #define DECLARE_TASK_QUEUE(q) LIST_HEAD(q)
67 #define TQ_ACTIVE(q) (!list_empty(&q))
68
69 extern task_queue tq_timer, tq_immediate, tq_disk;
70
71 /*
72 * To implement your own list of active bottom halfs, use the following
73 * two definitions:
74 *
75 * DECLARE_TASK_QUEUE(my_tqueue);
76 * struct tq_struct my_task = {
77 * routine: (void (*)(void *)) my_routine,
78 * data: &my_data
79 * };
80 *
81 * To activate a bottom half on a list, use:
82 *
83 * queue_task(&my_task, &my_tqueue);
84 *
85 * To later run the queued tasks use
86 *
87 * run_task_queue(&my_tqueue);
88 *
89 * This allows you to do deferred processing. For example, you could
90 * have a task queue called tq_timer, which is executed within the timer
91 * interrupt.
92 */
93
94 extern spinlock_t tqueue_lock;
95
96 /*
97 * Queue a task on a tq. Return non-zero if it was successfully
98 * added.
99 */
queue_task(struct tq_struct * bh_pointer,task_queue * bh_list)100 static inline int queue_task(struct tq_struct *bh_pointer, task_queue *bh_list)
101 {
102 int ret = 0;
103 if (!test_and_set_bit(0,&bh_pointer->sync)) {
104 unsigned long flags;
105 spin_lock_irqsave(&tqueue_lock, flags);
106 list_add_tail(&bh_pointer->list, bh_list);
107 spin_unlock_irqrestore(&tqueue_lock, flags);
108 ret = 1;
109 }
110 return ret;
111 }
112
113 /*
114 * Call all "bottom halfs" on a given list.
115 */
116
117 extern void __run_task_queue(task_queue *list);
118
run_task_queue(task_queue * list)119 static inline void run_task_queue(task_queue *list)
120 {
121 if (TQ_ACTIVE(*list))
122 __run_task_queue(list);
123 }
124
125 #endif /* _LINUX_TQUEUE_H */
126