2 * Copyright (C) 2006-2011 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 list_head pre_select_list, post_select_list;
23 static int initialized;
25 static struct timeval now_struct;
26 struct timeval *now = &now_struct;
29 * Remove a task from the scheduler.
31 * \param t The task to remove.
33 * If the pre_select pointer of \a t is not \p NULL, it is removed from
34 * the pre_select list of the scheduler. Same goes for \a post_select.
36 static void unregister_task(struct task *t)
41 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
42 para_strerror(-t->error));
44 list_del(&t->pre_select_node);
46 list_del(&t->post_select_node);
49 static void sched_preselect(struct sched *s)
52 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
55 // PARA_INFO_LOG("%s \n", t->status);
59 * We have to check whether the list is empty because the call
60 * to ->pre_select() might have called sched_shutdown(). In
61 * this case t has been unregistered already, so we must not
62 * unregister it again.
64 if (list_empty(&pre_select_list))
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, &post_select_list, post_select_node) {
96 call_post_select(s, t);
97 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
100 /* nec., see sched_preselect() */
101 if (list_empty(&post_select_list))
108 * The core function for all paraslash programs.
110 * \param s Pointer to the scheduler struct.
112 * This function updates the global \a now pointer, calls all registered
113 * pre_select hooks which may set the timeout and add any file descriptors to
114 * the fd sets of \a s. Next, it calls para_select() and makes the result available
115 * to the registered tasks by calling their post_select hook.
117 * \return Zero if no more tasks are left in either of the two lists, negative
118 * if para_select returned an error.
122 int schedule(struct sched *s)
127 return -E_NOT_INITIALIZED;
128 if (!s->select_function)
129 s->select_function = para_select;
133 s->select_timeout = s->default_timeout;
135 gettimeofday(now, NULL);
137 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
139 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
145 * APUE: Be careful not to check the descriptor sets on return
146 * unless the return value is greater than zero. The return
147 * state of the descriptor sets is implementation dependent if
148 * either a signal is caught or the timer expires.
153 gettimeofday(now, NULL);
154 sched_post_select(s);
155 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
161 * Initialize the paraslash scheduler.
163 static void init_sched(void)
165 PARA_INFO_LOG("initializing scheduler\n");
166 INIT_LIST_HEAD(&pre_select_list);
167 INIT_LIST_HEAD(&post_select_list);
172 * Add a task to the scheduler.
174 * \param t the task to add
176 * If the pre_select pointer of \a t is not \p NULL, it is added to
177 * the pre_select list of the scheduler. Same goes for post_select.
179 * \sa task::pre_select, task::post_select
181 void register_task(struct task *t)
185 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
187 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
188 list_add_tail(&t->pre_select_node, &pre_select_list);
190 if (t->post_select) {
191 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
192 list_add_tail(&t->post_select_node, &post_select_list);
197 * Unregister all tasks.
199 * This will cause \a schedule() to return immediately because both the
200 * \a pre_select_list and the \a post_select_list are empty.
202 void sched_shutdown(void)
204 struct task *t, *tmp;
208 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
209 t->error = -E_SCHED_SHUTDOWN;
212 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
213 t->error = -E_SCHED_SHUTDOWN;
220 * Get the list of all registered tasks.
222 * \return The task list.
224 * Each entry of the list contains an identifier which is simply a hex number.
225 * The result is dynamically allocated and must be freed by the caller.
227 char *get_task_list(void)
229 struct task *t, *tmp;
234 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
236 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
240 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
242 // if (t->pre_select)
244 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
248 //PARA_DEBUG_LOG("task list:\n%s", msg);
253 * Set the select timeout to the minimal possible value.
255 * \param s Pointer to the scheduler struct.
257 * This causes the next select() call to return immediately.
259 void sched_min_delay(struct sched *s)
261 s->select_timeout.tv_sec = 0;
262 s->select_timeout.tv_usec = 1;
266 * Impose an upper bound for the timeout of the next select() call.
268 * \param to Maximal allowed timeout.
269 * \param s Pointer to the scheduler struct.
271 * If the current scheduler timeout is already smaller than \a to, this
272 * function does nothing. Otherwise the timeout for the next select() call is
273 * set to the given value.
275 * \sa sched_request_timeout_ms().
277 void sched_request_timeout(struct timeval *to, struct sched *s)
279 if (tv_diff(&s->select_timeout, to, NULL) > 0)
280 s->select_timeout = *to;
284 * Force the next select() call to return before the given amount of milliseconds.
286 * \param ms The maximal allowed timeout in milliseconds.
287 * \param s Pointer to the scheduler struct.
289 * Like sched_request_timeout() this imposes an upper bound on the timeout
290 * value for the next select() call.
292 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
296 sched_request_timeout(&tv, s);
300 * Force the next select() call to return before the given future time.
302 * \param barrier Absolute time before select() should return.
303 * \param s Pointer to the scheduler struct.
305 * If \a barrier is in the past, this function does nothing.
307 * \sa sched_request_barrier_or_min_delay().
309 void sched_request_barrier(struct timeval *barrier, struct sched *s)
313 if (tv_diff(now, barrier, &diff) > 0)
315 sched_request_timeout(&diff, s);
319 * Force the next select() call to return before the given time.
321 * \param barrier Absolute time before select() should return.
322 * \param s Pointer to the scheduler struct.
324 * If \a barrier is in the past, this function requests a minimal timeout.
326 * \sa sched_min_delay(), sched_request_barrier().
328 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
332 if (tv_diff(now, barrier, &diff) > 0)
333 return sched_min_delay(s);
334 sched_request_timeout(&diff, s);