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. */
10 #include <dirent.h> /* readdir() */
23 static struct list_head pre_select_list, post_select_list;
24 static int initialized;
26 static struct timeval now_struct;
27 struct timeval *now = &now_struct;
30 * Remove a task from the scheduler.
32 * \param t The task to remove.
34 * If the pre_select pointer of \a t is not \p NULL, it is removed from
35 * the pre_select list of the scheduler. Same goes for \a post_select.
37 static void unregister_task(struct task *t)
42 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
43 para_strerror(-t->error));
45 list_del(&t->pre_select_node);
47 list_del(&t->post_select_node);
50 static void sched_preselect(struct sched *s)
53 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
56 // PARA_INFO_LOG("%s \n", t->status);
60 * We have to check whether the list is empty because the call
61 * to ->pre_select() might have called sched_shutdown(). In
62 * this case t has been unregistered already, so we must not
63 * unregister it again.
65 if (list_empty(&pre_select_list))
71 //#define SCHED_DEBUG 1
72 static inline void call_post_select(struct sched *s, struct task *t)
77 struct timeval t1, t2, diff;
80 gettimeofday(&t1, NULL);
82 gettimeofday(&t2, NULL);
83 tv_diff(&t1, &t2, &diff);
86 PARA_WARNING_LOG("%s: post_select time: %lums\n",
91 static void sched_post_select(struct sched *s)
95 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
97 call_post_select(s, t);
98 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
101 /* nec., see sched_preselect() */
102 if (list_empty(&post_select_list))
109 * The core function for all paraslash programs.
111 * \param s Pointer to the scheduler struct.
113 * This function updates the global \a now pointer, calls all registered
114 * pre_select hooks which may set the timeout and add any file descriptors to
115 * the fd sets of \a s. Next, it calls para_select() and makes the result available
116 * to the registered tasks by calling their post_select hook.
118 * \return Zero if no more tasks are left in either of the two lists, negative
119 * if para_select returned an error.
123 int schedule(struct sched *s)
128 return -E_NOT_INITIALIZED;
129 if (!s->select_function)
130 s->select_function = para_select;
134 s->select_timeout = s->default_timeout;
136 gettimeofday(now, NULL);
138 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
140 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
146 * APUE: Be careful not to check the descriptor sets on return
147 * unless the return value is greater than zero. The return
148 * state of the descriptor sets is implementation dependent if
149 * either a signal is caught or the timer expires.
154 gettimeofday(now, NULL);
155 sched_post_select(s);
156 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
162 * Initialize the paraslash scheduler.
164 static void init_sched(void)
166 PARA_INFO_LOG("initializing scheduler\n");
167 INIT_LIST_HEAD(&pre_select_list);
168 INIT_LIST_HEAD(&post_select_list);
173 * Add a task to the scheduler.
175 * \param t the task to add
177 * If the pre_select pointer of \a t is not \p NULL, it is added to
178 * the pre_select list of the scheduler. Same goes for post_select.
180 * \sa task::pre_select, task::post_select
182 void register_task(struct task *t)
186 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
188 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
189 list_add_tail(&t->pre_select_node, &pre_select_list);
191 if (t->post_select) {
192 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
193 list_add_tail(&t->post_select_node, &post_select_list);
198 * Unregister all tasks.
200 * This will cause \a schedule() to return immediately because both the
201 * \a pre_select_list and the \a post_select_list are empty.
203 void sched_shutdown(void)
205 struct task *t, *tmp;
209 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
210 t->error = -E_SCHED_SHUTDOWN;
213 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
214 t->error = -E_SCHED_SHUTDOWN;
221 * Get the list of all registered tasks.
223 * \return The task list.
225 * Each entry of the list contains an identifier which is simply a hex number.
226 * The result is dynamically allocated and must be freed by the caller.
228 char *get_task_list(void)
230 struct task *t, *tmp;
235 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
237 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
241 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
243 // if (t->pre_select)
245 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
249 //PARA_DEBUG_LOG("task list:\n%s", msg);
254 * Set the select timeout to the minimal possible value.
256 * \param s Pointer to the scheduler struct.
258 * This causes the next select() call to return immediately.
260 void sched_min_delay(struct sched *s)
262 s->select_timeout.tv_sec = 0;
263 s->select_timeout.tv_usec = 1;
267 * Impose an upper bound for the timeout of the next select() call.
269 * \param to Maximal allowed timeout.
270 * \param s Pointer to the scheduler struct.
272 * If the current scheduler timeout is already smaller than \a to, this
273 * function does nothing. Otherwise the timeout for the next select() call is
274 * set to the given value.
276 * \sa sched_request_timeout_ms().
278 void sched_request_timeout(struct timeval *to, struct sched *s)
280 if (tv_diff(&s->select_timeout, to, NULL) > 0)
281 s->select_timeout = *to;
285 * Force the next select() call to return before the given amount of milliseconds.
287 * \param ms The maximal allowed timeout in milliseconds.
288 * \param s Pointer to the scheduler struct.
290 * Like sched_request_timeout() this imposes an upper bound on the timeout
291 * value for the next select() call.
293 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
297 sched_request_timeout(&tv, s);
301 * Force the next select() call to return before the given future time.
303 * \param barrier Absolute time before select() should return.
304 * \param s Pointer to the scheduler struct.
306 * If \a barrier is in the past, this function does nothing.
308 * \sa sched_request_barrier_or_min_delay().
310 void sched_request_barrier(struct timeval *barrier, struct sched *s)
314 if (tv_diff(now, barrier, &diff) > 0)
316 sched_request_timeout(&diff, s);
320 * Force the next select() call to return before the given time.
322 * \param barrier Absolute time before select() should return.
323 * \param s Pointer to the scheduler struct.
325 * If \a barrier is in the past, this function requests a minimal timeout.
327 * \sa sched_min_delay(), sched_request_barrier().
329 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
333 if (tv_diff(now, barrier, &diff) > 0)
334 return sched_min_delay(s);
335 sched_request_timeout(&diff, s);