sched: Introduce alternative task API.
[paraslash.git] / sched.h
1 /*
2 * Copyright (C) 2006-2014 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 maintains a list of task structures which is
14 * extended when a new task is registered. Each task may define a pre_select
15 * function which is called from the scheduler main loop before it calls
16 * select(). Similarly, each task must define a post_select function which is
17 * called after the select call.
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 /** Tasks which have been registered to the scheduler. */
33 struct list_head task_list;
34 };
35
36 /**
37 * Paraslash's task structure.
38 *
39 * This is considered an internal structure and will eventually be made private.
40 *
41 * \sa \ref sched.
42 */
43 struct task {
44 /** Copied from the task_info struct during task_register(). */
45 void (*pre_select)(struct sched *s, struct task *t);
46 /** Copied from the task_info struct during task_register(). */
47 int (*post_select)(struct sched *s, struct task *t);
48 /** Whether this task is active (>=0) or in error state (<0). */
49 int error;
50 /** Position of the task in the task list of the scheduler. */
51 struct list_head node;
52 /** The task name supplied when the task was registered(). */
53 char status[255];
54 /** If less than zero, the task was notified by another task. */
55 int notification;
56 /** Whether the task structure should be freed in sched_shutdown(). */
57 bool owned_by_sched;
58 /** Usually a pointer to the struct containing this task. */
59 void *context;
60 };
61
62 /** Information that must be supplied by callers of \ref task_register(). */
63 struct task_info {
64 /** Used for log messages and by \ref get_task_list(). */
65 const char *name;
66 /**
67 * The optional pre select method.
68 *
69 * Its purpose is to add file descriptors to the fd sets of the
70 * scheduler and to decrease the select timeout if necessary.
71 */
72 void (*pre_select)(struct sched *s, struct task *t);
73 /**
74 * The mandatory post select method.
75 *
76 * Its purpose is to evaluate and act upon the results of the previous
77 * select call. If this function returns a negative value, the
78 * scheduler unregisters the task.
79 */
80 int (*post_select)(struct sched *s, struct task *t);
81 /**
82 * This pointer is saved when the task is register(ed). It may be
83 * queried from ->pre_select() and ->post_select() via \ref
84 * task_context(). Usually this is a pointer to the struct owned by the
85 * caller which contains the task pointer as one member.
86 */
87 void *context;
88 };
89
90 /**
91 * This is set by the scheduler at the beginning of its main loop. It may be
92 * used (read-only) from everywhere. As none of the functions called by the
93 * scheduler are allowed to block, this value should be accurate enough so that
94 * there is no need to call clock_gettime() directly.
95 */
96 extern struct timeval *now;
97
98 struct task *task_register(struct task_info *info, struct sched *s);
99 void *task_context(struct task *t);
100 void register_task(struct sched *s, struct task *t);
101 int schedule(struct sched *s);
102 void sched_shutdown(struct sched *s);
103 char *get_task_list(struct sched *s);
104 void task_notify(struct task *t, int err);
105 void task_notify_all(struct sched *s, int err);
106 int task_get_notification(const struct task *t);
107 void sched_min_delay(struct sched *s);
108 void sched_request_timeout(struct timeval *to, struct sched *s);
109 void sched_request_timeout_ms(long unsigned ms, struct sched *s);
110 int sched_request_barrier(struct timeval *barrier, struct sched *s);
111 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);