2 * Copyright (C) 2006-2013 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file sched.h Sched and task structures and exported symbols from sched.c. */
11 * Paraslash's scheduler.
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.
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. */
26 /** fds that should be watched for writability. */
28 /** Highest numbered file descriptor in any of the above fd sets. */
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;
39 * Paraslash's task structure.
41 * Before registering a task to the scheduler, the task structure must be
42 * filled in properly by the caller.
44 * If one of these functions sets \a t->error to a negative value, the
45 * task gets unregistered automatically.
51 * The pre select hook of \a t.
53 * Its purpose is to add file descriptors to the fd sets of the
54 * scheduler and to decrease the select timeout if necessary.
56 void (*pre_select)(struct sched *s, struct task *t);
58 * The postselect hook of \a t.
60 * Evaluate and act upon the results of the previous select call.
62 void (*post_select)(struct sched *s, struct task *t);
64 * The newer variant of the post select hook of \a t.
66 * This hook must return the error code rather than store it in
69 int (*new_post_select)(struct sched *s, struct task *t);
70 /** Whether this task is in error state. */
72 /** Position of the task in the pre_select list of the scheduler. */
73 struct list_head pre_select_node;
74 /** Position of the task in the post_select list of the scheduler. */
75 struct list_head post_select_node;
76 /** Descriptive text and current status of the task. */
78 /** If less than zero, the task was notified by another task. */
83 * This is set by the scheduler at the beginning of its main loop. It may be
84 * used (read-only) from everywhere. As none of the functions called by the
85 * scheduler are allowed to block, this value should be accurate enough so that
86 * there is no need to call clock_gettime() directly.
88 extern struct timeval *now;
90 void register_task(struct sched *s, struct task *t);
91 int schedule(struct sched *s);
92 char *get_task_list(struct sched *s);
93 void task_notify(struct task *t, int err);
94 void task_notify_all(struct sched *s, int err);
95 int task_get_notification(struct task *t);
96 void sched_min_delay(struct sched *s);
97 void sched_request_timeout(struct timeval *to, struct sched *s);
98 void sched_request_timeout_ms(long unsigned ms, struct sched *s);
99 int sched_request_barrier(struct timeval *barrier, struct sched *s);
100 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s);