2 * Copyright (C) 2006-2013 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file sched.c Paraslash's scheduling functions. */
22 static struct timeval now_struct;
23 struct timeval *now = &now_struct;
26 * Remove a task from the scheduler.
28 * \param t The task to remove.
30 * If the pre_select pointer of \a t is not \p NULL, it is removed from
31 * the pre_select list of the scheduler. Same goes for \a post_select.
33 static void unregister_task(struct task *t)
36 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
37 para_strerror(-t->error));
39 list_del(&t->pre_select_node);
41 list_del(&t->post_select_node);
44 static inline bool timeout_is_zero(struct sched *s)
46 struct timeval *tv = &s->select_timeout;
47 return tv->tv_sec == 0 && tv->tv_usec == 0;
50 static void sched_preselect(struct sched *s)
53 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
58 if (t->notification != 0) {
65 if (timeout_is_zero(s))
70 //#define SCHED_DEBUG 1
71 static inline void call_post_select(struct sched *s, struct task *t)
76 struct timeval t1, t2, diff;
79 gettimeofday(&t1, NULL);
81 gettimeofday(&t2, NULL);
82 tv_diff(&t1, &t2, &diff);
85 PARA_WARNING_LOG("%s: post_select time: %lums\n",
90 static void sched_post_select(struct sched *s)
94 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
96 call_post_select(s, t);
97 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
106 * The core function for all paraslash programs.
108 * \param s Pointer to the scheduler struct.
110 * This function updates the global \a now pointer, calls all registered
111 * pre_select hooks which may set the timeout and add any file descriptors to
112 * the fd sets of \a s. Next, it calls para_select() and makes the result available
113 * to the registered tasks by calling their post_select hook.
115 * \return Zero if no more tasks are left in either of the two lists, negative
116 * if para_select returned an error.
120 int schedule(struct sched *s)
124 if (!s->select_function)
125 s->select_function = para_select;
129 s->select_timeout = s->default_timeout;
131 gettimeofday(now, NULL);
133 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
135 if (!timeout_is_zero(s)) {
136 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
142 * APUE: Be careful not to check the descriptor sets on return
143 * unless the return value is greater than zero. The return
144 * state of the descriptor sets is implementation dependent if
145 * either a signal is caught or the timer expires.
150 gettimeofday(now, NULL);
155 sched_post_select(s);
156 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
162 * Add a task to the scheduler.
164 * \param t The task to add.
165 * \param s The scheduler instance to add the task to.
167 * If the pre_select pointer of \a t is not \p NULL, it is added to
168 * the pre_select list of the scheduler. Same goes for post_select.
170 * \sa task::pre_select, task::post_select
172 void register_task(struct sched *s, struct task *t)
174 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
176 if (!s->pre_select_list.next)
177 INIT_LIST_HEAD(&s->pre_select_list);
178 if (!s->post_select_list.next)
179 INIT_LIST_HEAD(&s->post_select_list);
181 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
182 list_add_tail(&t->pre_select_node, &s->pre_select_list);
184 if (t->post_select) {
185 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
186 list_add_tail(&t->post_select_node, &s->post_select_list);
191 * Get the list of all registered tasks.
193 * \param s The scheduler instance to get the task list from.
195 * \return The task list.
197 * Each entry of the list contains an identifier which is simply a hex number.
198 * The result is dynamically allocated and must be freed by the caller.
200 char *get_task_list(struct sched *s)
202 struct task *t, *tmp;
205 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
207 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
211 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
213 // if (t->pre_select)
215 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
219 //PARA_DEBUG_LOG("task list:\n%s", msg);
224 * Set the notification value of a task.
226 * \param t The task to notify.
227 * \param err A positive error code.
229 * Tasks which honor notifications are supposed to call \ref
230 * task_get_notification() in their post_select function and act on the
231 * returned notification value.
233 * If the scheduler detects during its pre_select loop that at least one task
234 * has been notified, the loop terminates, and the post_select methods of all
235 * taks are immediately called again.
237 * The notification for a task is reset after the call to its post_select
240 * \sa \ref task_get_notification().
242 void task_notify(struct task *t, int err)
245 if (t->notification == -err) /* ignore subsequent notifications */
247 PARA_INFO_LOG("notifying task %s: %s\n", t->status, para_strerror(err));
248 t->notification = -err;
252 * Return the notification value of a task.
254 * \param t The task to get the notification value from.
256 * \return The notification value. If this is negative, the task has been
257 * notified by another task. Tasks are supposed to check for notifications by
258 * calling this function from their post_select method.
260 * \sa \ref task_notify().
262 int task_get_notification(struct task *t)
264 return t->notification;
268 * Set the notification value of all tasks of a scheduler instance.
270 * \param s The scheduler instance whose tasks should be notified.
271 * \param err A positive error code.
273 * This simply iterates over all existing tasks of \a s and sets each
274 * task's notification value to \p -err.
276 void task_notify_all(struct sched *s, int err)
280 list_for_each_entry(t, &s->pre_select_list, pre_select_node)
282 list_for_each_entry(t, &s->post_select_list, post_select_node)
287 * Set the select timeout to the minimal possible value.
289 * \param s Pointer to the scheduler struct.
291 * This causes the next select() call to return immediately.
293 void sched_min_delay(struct sched *s)
295 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
299 * Impose an upper bound for the timeout of the next select() call.
301 * \param to Maximal allowed timeout.
302 * \param s Pointer to the scheduler struct.
304 * If the current scheduler timeout is already smaller than \a to, this
305 * function does nothing. Otherwise the timeout for the next select() call is
306 * set to the given value.
308 * \sa sched_request_timeout_ms().
310 void sched_request_timeout(struct timeval *to, struct sched *s)
312 if (tv_diff(&s->select_timeout, to, NULL) > 0)
313 s->select_timeout = *to;
317 * Force the next select() call to return before the given amount of milliseconds.
319 * \param ms The maximal allowed timeout in milliseconds.
320 * \param s Pointer to the scheduler struct.
322 * Like sched_request_timeout() this imposes an upper bound on the timeout
323 * value for the next select() call.
325 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
329 sched_request_timeout(&tv, s);
333 * Force the next select() call to return before the given future time.
335 * \param barrier Absolute time before select() should return.
336 * \param s Pointer to the scheduler struct.
338 * \return If \a barrier is in the past, this function does nothing and returns
339 * zero. Otherwise it returns one.
341 * \sa sched_request_barrier_or_min_delay().
343 int sched_request_barrier(struct timeval *barrier, struct sched *s)
347 if (tv_diff(now, barrier, &diff) > 0)
349 sched_request_timeout(&diff, s);
354 * Force the next select() call to return before the given time.
356 * \param barrier Absolute time before select() should return.
357 * \param s Pointer to the scheduler struct.
359 * \return If \a barrier is in the past, this function requests a minimal
360 * timeout and returns zero. Otherwise it returns one.
362 * \sa sched_min_delay(), sched_request_barrier().
364 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
368 if (tv_diff(now, barrier, &diff) > 0) {
372 sched_request_timeout(&diff, s);