2 * Copyright (C) 2006-2012 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);
102 * We have to check whether the list is empty because the call
103 * to ->post_select() might have called sched_shutdown(). In
104 * this case t has been unregistered already, so we must not
105 * unregister it again.
107 if (list_empty(&s->post_select_list))
114 * The core function for all paraslash programs.
116 * \param s Pointer to the scheduler struct.
118 * This function updates the global \a now pointer, calls all registered
119 * pre_select hooks which may set the timeout and add any file descriptors to
120 * the fd sets of \a s. Next, it calls para_select() and makes the result available
121 * to the registered tasks by calling their post_select hook.
123 * \return Zero if no more tasks are left in either of the two lists, negative
124 * if para_select returned an error.
128 int schedule(struct sched *s)
132 if (!s->select_function)
133 s->select_function = para_select;
137 s->select_timeout = s->default_timeout;
139 gettimeofday(now, NULL);
141 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
143 if (!timeout_is_zero(s)) {
144 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
150 * APUE: Be careful not to check the descriptor sets on return
151 * unless the return value is greater than zero. The return
152 * state of the descriptor sets is implementation dependent if
153 * either a signal is caught or the timer expires.
158 gettimeofday(now, NULL);
163 sched_post_select(s);
164 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
170 * Add a task to the scheduler.
172 * \param t The task to add.
173 * \param s The scheduler instance to add the task to.
175 * If the pre_select pointer of \a t is not \p NULL, it is added to
176 * the pre_select list of the scheduler. Same goes for post_select.
178 * \sa task::pre_select, task::post_select
180 void register_task(struct sched *s, struct task *t)
182 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
184 if (!s->pre_select_list.next)
185 INIT_LIST_HEAD(&s->pre_select_list);
186 if (!s->post_select_list.next)
187 INIT_LIST_HEAD(&s->post_select_list);
189 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
190 list_add_tail(&t->pre_select_node, &s->pre_select_list);
192 if (t->post_select) {
193 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
194 list_add_tail(&t->post_select_node, &s->post_select_list);
199 * Unregister all tasks.
201 * \param s The scheduler instance to shut down.
203 * This will cause \a schedule() to return immediately because both the
204 * \a pre_select_list and the \a post_select_list are empty. This function
205 * must be called from the post_select (rather than the pre_select) method.
207 void sched_shutdown(struct sched *s)
209 struct task *t, *tmp;
211 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
212 t->error = -E_SCHED_SHUTDOWN;
215 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
216 t->error = -E_SCHED_SHUTDOWN;
222 * Get the list of all registered tasks.
224 * \param s The scheduler instance to get the task list from.
226 * \return The task list.
228 * Each entry of the list contains an identifier which is simply a hex number.
229 * The result is dynamically allocated and must be freed by the caller.
231 char *get_task_list(struct sched *s)
233 struct task *t, *tmp;
236 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
238 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
242 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
244 // if (t->pre_select)
246 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
250 //PARA_DEBUG_LOG("task list:\n%s", msg);
255 * Set the notification value of a task.
257 * \param t The task to notify.
258 * \param err A positive error code.
260 * Tasks which honor notifications are supposed to call \ref
261 * task_get_notification() in their post_select function and act on the
262 * returned notification value.
264 * If the scheduler detects during its pre_select loop that at least one task
265 * has been notified, the loop terminates, and the post_select methods of all
266 * taks are immediately called again.
268 * The notification for a task is reset after the call to its post_select
271 * \sa \ref task_get_notification().
273 void task_notify(struct task *t, int err)
276 if (t->notification == -err) /* ignore subsequent notifications */
278 PARA_INFO_LOG("notifying task %s: %s\n", t->status, para_strerror(err));
279 t->notification = -err;
283 * Return the notification value of a task.
285 * \param t The task to get the notification value from.
287 * \return The notification value. If this is negative, the task has been
288 * notified by another task. Tasks are supposed to check for notifications by
289 * calling this function from their post_select method.
291 * \sa \ref task_notify().
293 int task_get_notification(struct task *t)
295 return t->notification;
299 * Set the select timeout to the minimal possible value.
301 * \param s Pointer to the scheduler struct.
303 * This causes the next select() call to return immediately.
305 void sched_min_delay(struct sched *s)
307 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
311 * Impose an upper bound for the timeout of the next select() call.
313 * \param to Maximal allowed timeout.
314 * \param s Pointer to the scheduler struct.
316 * If the current scheduler timeout is already smaller than \a to, this
317 * function does nothing. Otherwise the timeout for the next select() call is
318 * set to the given value.
320 * \sa sched_request_timeout_ms().
322 void sched_request_timeout(struct timeval *to, struct sched *s)
324 if (tv_diff(&s->select_timeout, to, NULL) > 0)
325 s->select_timeout = *to;
329 * Force the next select() call to return before the given amount of milliseconds.
331 * \param ms The maximal allowed timeout in milliseconds.
332 * \param s Pointer to the scheduler struct.
334 * Like sched_request_timeout() this imposes an upper bound on the timeout
335 * value for the next select() call.
337 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
341 sched_request_timeout(&tv, s);
345 * Force the next select() call to return before the given future time.
347 * \param barrier Absolute time before select() should return.
348 * \param s Pointer to the scheduler struct.
350 * \return If \a barrier is in the past, this function does nothing and returns
351 * zero. Otherwise it returns one.
353 * \sa sched_request_barrier_or_min_delay().
355 int sched_request_barrier(struct timeval *barrier, struct sched *s)
359 if (tv_diff(now, barrier, &diff) > 0)
361 sched_request_timeout(&diff, s);
366 * Force the next select() call to return before the given time.
368 * \param barrier Absolute time before select() should return.
369 * \param s Pointer to the scheduler struct.
371 * \return If \a barrier is in the past, this function requests a minimal
372 * timeout and returns zero. Otherwise it returns one.
374 * \sa sched_min_delay(), sched_request_barrier().
376 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
380 if (tv_diff(now, barrier, &diff) > 0) {
384 sched_request_timeout(&diff, s);