2 * Copyright (C) 2006-2014 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file sched.c Paraslash's scheduling functions. */
21 static struct timeval now_struct;
22 struct timeval *now = &now_struct;
25 * Remove a task from the scheduler.
27 * \param t The task to remove.
29 * If the pre_select pointer of \a t is not \p NULL, it is removed from
30 * the pre_select list of the scheduler. Same goes for \a post_select.
32 static void unregister_task(struct task *t)
35 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
36 para_strerror(-t->error));
38 list_del(&t->pre_select_node);
40 list_del(&t->post_select_node);
43 static inline bool timeout_is_zero(struct sched *s)
45 struct timeval *tv = &s->select_timeout;
46 return tv->tv_sec == 0 && tv->tv_usec == 0;
49 static void sched_preselect(struct sched *s)
53 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
54 if (t->notification != 0)
61 //#define SCHED_DEBUG 1
62 static inline void call_post_select(struct sched *s, struct task *t)
65 t->error = t->post_select(s, t);
67 struct timeval t1, t2, diff;
70 clock_get_realtime(&t1);
71 t->error = t->post_select(s, t);
72 clock_get_realtime(&t2);
73 tv_diff(&t1, &t2, &diff);
76 PARA_WARNING_LOG("%s: post_select time: %lums\n",
81 static void sched_post_select(struct sched *s)
85 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
87 call_post_select(s, t);
88 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
97 * The core function for all paraslash programs.
99 * \param s Pointer to the scheduler struct.
101 * This function updates the global \a now pointer, calls all registered
102 * pre_select hooks which may set the timeout and add any file descriptors to
103 * the fd sets of \a s. Next, it calls para_select() and makes the result available
104 * to the registered tasks by calling their post_select hook.
106 * \return Zero if no more tasks are left in either of the two lists, negative
107 * if para_select returned an error.
111 int schedule(struct sched *s)
115 if (!s->select_function)
116 s->select_function = para_select;
120 s->select_timeout = s->default_timeout;
122 clock_get_realtime(now);
124 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
130 * APUE: Be careful not to check the descriptor sets on return
131 * unless the return value is greater than zero. The return
132 * state of the descriptor sets is implementation dependent if
133 * either a signal is caught or the timer expires.
138 clock_get_realtime(now);
139 sched_post_select(s);
140 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
146 * Add a task to the scheduler.
148 * \param t The task to add.
149 * \param s The scheduler instance to add the task to.
151 * If the pre_select pointer of \a t is not \p NULL, it is added to
152 * the pre_select list of the scheduler. Same goes for post_select.
154 * \sa task::pre_select, task::post_select
156 void register_task(struct sched *s, struct task *t)
158 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
160 if (!s->pre_select_list.next)
161 INIT_LIST_HEAD(&s->pre_select_list);
162 if (!s->post_select_list.next)
163 INIT_LIST_HEAD(&s->post_select_list);
165 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
166 list_add_tail(&t->pre_select_node, &s->pre_select_list);
168 if (t->post_select) {
169 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
170 list_add_tail(&t->post_select_node, &s->post_select_list);
175 * Get the list of all registered tasks.
177 * \param s The scheduler instance to get the task list from.
179 * \return The task list.
181 * Each entry of the list contains an identifier which is simply a hex number.
182 * The result is dynamically allocated and must be freed by the caller.
184 char *get_task_list(struct sched *s)
186 struct task *t, *tmp;
189 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
191 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
195 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
197 // if (t->pre_select)
199 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
203 //PARA_DEBUG_LOG("task list:\n%s", msg);
208 * Set the notification value of a task.
210 * \param t The task to notify.
211 * \param err A positive error code.
213 * Tasks which honor notifications are supposed to call \ref
214 * task_get_notification() in their post_select function and act on the
215 * returned notification value.
217 * If the scheduler detects during its pre_select loop that at least one task
218 * has been notified, the loop terminates, and the post_select methods of all
219 * taks are immediately called again.
221 * The notification for a task is reset after the call to its post_select
224 * \sa \ref task_get_notification().
226 void task_notify(struct task *t, int err)
229 if (t->notification == -err) /* ignore subsequent notifications */
231 PARA_INFO_LOG("notifying task %s: %s\n", t->status, para_strerror(err));
232 t->notification = -err;
236 * Return the notification value of a task.
238 * \param t The task to get the notification value from.
240 * \return The notification value. If this is negative, the task has been
241 * notified by another task. Tasks are supposed to check for notifications by
242 * calling this function from their post_select method.
244 * \sa \ref task_notify().
246 int task_get_notification(struct task *t)
248 return t->notification;
252 * Set the notification value of all tasks of a scheduler instance.
254 * \param s The scheduler instance whose tasks should be notified.
255 * \param err A positive error code.
257 * This simply iterates over all existing tasks of \a s and sets each
258 * task's notification value to \p -err.
260 void task_notify_all(struct sched *s, int err)
264 list_for_each_entry(t, &s->pre_select_list, pre_select_node)
266 list_for_each_entry(t, &s->post_select_list, post_select_node)
271 * Set the select timeout to the minimal possible value.
273 * \param s Pointer to the scheduler struct.
275 * This causes the next select() call to return immediately.
277 void sched_min_delay(struct sched *s)
279 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
283 * Impose an upper bound for the timeout of the next select() call.
285 * \param to Maximal allowed timeout.
286 * \param s Pointer to the scheduler struct.
288 * If the current scheduler timeout is already smaller than \a to, this
289 * function does nothing. Otherwise the timeout for the next select() call is
290 * set to the given value.
292 * \sa sched_request_timeout_ms().
294 void sched_request_timeout(struct timeval *to, struct sched *s)
296 if (tv_diff(&s->select_timeout, to, NULL) > 0)
297 s->select_timeout = *to;
301 * Force the next select() call to return before the given amount of milliseconds.
303 * \param ms The maximal allowed timeout in milliseconds.
304 * \param s Pointer to the scheduler struct.
306 * Like sched_request_timeout() this imposes an upper bound on the timeout
307 * value for the next select() call.
309 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
313 sched_request_timeout(&tv, s);
317 * Force the next select() call to return before the given future time.
319 * \param barrier Absolute time before select() should return.
320 * \param s Pointer to the scheduler struct.
322 * \return If \a barrier is in the past, this function does nothing and returns
323 * zero. Otherwise it returns one.
325 * \sa sched_request_barrier_or_min_delay().
327 int sched_request_barrier(struct timeval *barrier, struct sched *s)
331 if (tv_diff(now, barrier, &diff) > 0)
333 sched_request_timeout(&diff, s);
338 * Force the next select() call to return before the given time.
340 * \param barrier Absolute time before select() should return.
341 * \param s Pointer to the scheduler struct.
343 * \return If \a barrier is in the past, this function requests a minimal
344 * timeout and returns zero. Otherwise it returns one.
346 * \sa sched_min_delay(), sched_request_barrier().
348 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
352 if (tv_diff(now, barrier, &diff) > 0) {
356 sched_request_timeout(&diff, s);