b3df0b66b180bd1f3f2f48f784c07a187fbac712
[paraslash.git] / sched.h
1 /*
2 * Copyright (C) 2006-2011 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file sched.h Sched and task structures and exported symbols from sched.c. */
8
9
10 /**
11 * Paraslash's scheduler.
12 *
13 * Designed with KISS in mind. It manages two lists of tasks. The pre_select
14 * list contains pointers to functions that are called before calling select()
15 * from the main loop. Similarly, \a post_select_list is a list of function
16 * pointers each of which is called after the select call. Tasks add hooks to
17 * these lists by registering themselves to the scheduler.
18 */
19 struct sched {
20 /** Initial value before any pre_select call. */
21 struct timeval default_timeout;
22 /** The current timeout for the upcoming select call. */
23 struct timeval select_timeout;
24 /** fds that should be watched for readability. */
25 fd_set rfds;
26 /** fds that should be watched for writability. */
27 fd_set wfds;
28 /** Highest numbered file descriptor in any of the above fd sets. */
29 int max_fileno;
30 /** If non-NULL, use this function instead of para_select. */
31 int (*select_function)(int, fd_set *, fd_set *, struct timeval *);
32 /** Currently active pre_select functions. */
33 struct list_head pre_select_list;
34 /** Currently active post_select functions. */
35 struct list_head post_select_list;
36 };
37
38 /**
39 * Paraslash's task structure.
40 *
41 * Before registering a task to the scheduler, the task structure must be
42 * filled in properly by the caller.
43 *
44 * If one of these functions sets \a t->error to a negative value, the
45 * task gets unregistered automatically.
46 *
47 * \sa struct sched.
48 */
49 struct task {
50 /**
51 * The pre select hook of \a t.
52 *
53 * Its purpose is to add file descriptors to the fd sets of the
54 * scheduler and to decrease the select timeout if necessary.
55 */
56 void (*pre_select)(struct sched *s, struct task *t);
57 /**
58 * The postselect hook of \a t.
59 *
60 * Evaluate and act upon the results of the previous select call.
61 */
62 void (*post_select)(struct sched *s, struct task *t);
63 /** Whether this task is in error state. */
64 int error;
65 /** Position of the task in the pre_select list of the scheduler. */
66 struct list_head pre_select_node;
67 /** Position of the task in the post_select list of the scheduler. */
68 struct list_head post_select_node;
69 /** Descriptive text and current status of the task. */
70 char status[255];
71 };
72
73 /**
74 * This is set by the scheduler at the beginning of its main loop. It may be
75 * used (read-only) from everywhere. As none of the functions called by the
76 * scheduler are allowed to block, this value should be accurate enough so that
77 * there is no need to call gettimeofday() directly.
78 */
79 extern struct timeval *now;
80
81 void register_task(struct sched *s, struct task *t);
82 int schedule(struct sched *s);
83 char *get_task_list(struct sched *s);
84 void sched_shutdown(struct sched *s);
85 void sched_min_delay(struct sched *s);
86 void sched_request_timeout(struct timeval *to, struct sched *s);
87 void sched_request_timeout_ms(long unsigned ms, struct sched *s);
88 int sched_request_barrier(struct timeval *barrier, struct sched *s);
89 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);