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) {
60 //#define SCHED_DEBUG 1
61 static inline void call_post_select(struct sched *s, struct task *t)
66 struct timeval t1, t2, diff;
69 gettimeofday(&t1, NULL);
71 gettimeofday(&t2, NULL);
72 tv_diff(&t1, &t2, &diff);
75 PARA_WARNING_LOG("%s: post_select time: %lums\n",
80 static void sched_post_select(struct sched *s)
84 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
86 call_post_select(s, t);
87 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
91 * We have to check whether the list is empty because the call
92 * to ->post_select() might have called sched_shutdown(). In
93 * this case t has been unregistered already, so we must not
94 * unregister it again.
96 if (list_empty(&post_select_list))
103 * The core function for all paraslash programs.
105 * \param s Pointer to the scheduler struct.
107 * This function updates the global \a now pointer, calls all registered
108 * pre_select hooks which may set the timeout and add any file descriptors to
109 * the fd sets of \a s. Next, it calls para_select() and makes the result available
110 * to the registered tasks by calling their post_select hook.
112 * \return Zero if no more tasks are left in either of the two lists, negative
113 * if para_select returned an error.
117 int schedule(struct sched *s)
122 return -E_NOT_INITIALIZED;
123 if (!s->select_function)
124 s->select_function = para_select;
128 s->select_timeout = s->default_timeout;
130 gettimeofday(now, NULL);
132 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
134 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
140 * APUE: Be careful not to check the descriptor sets on return
141 * unless the return value is greater than zero. The return
142 * state of the descriptor sets is implementation dependent if
143 * either a signal is caught or the timer expires.
148 gettimeofday(now, NULL);
149 sched_post_select(s);
150 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
156 * Initialize the paraslash scheduler.
158 static void init_sched(void)
160 PARA_INFO_LOG("initializing scheduler\n");
161 INIT_LIST_HEAD(&pre_select_list);
162 INIT_LIST_HEAD(&post_select_list);
167 * Add a task to the scheduler.
169 * \param t the task to add
171 * If the pre_select pointer of \a t is not \p NULL, it is added to
172 * the pre_select list of the scheduler. Same goes for post_select.
174 * \sa task::pre_select, task::post_select
176 void register_task(struct task *t)
180 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
182 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
183 list_add_tail(&t->pre_select_node, &pre_select_list);
185 if (t->post_select) {
186 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
187 list_add_tail(&t->post_select_node, &post_select_list);
192 * Unregister all tasks.
194 * This will cause \a schedule() to return immediately because both the
195 * \a pre_select_list and the \a post_select_list are empty. This function
196 * must be called from the post_select (rather than the pre_select) method.
198 void sched_shutdown(void)
200 struct task *t, *tmp;
204 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
205 t->error = -E_SCHED_SHUTDOWN;
208 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
209 t->error = -E_SCHED_SHUTDOWN;
216 * Get the list of all registered tasks.
218 * \return The task list.
220 * Each entry of the list contains an identifier which is simply a hex number.
221 * The result is dynamically allocated and must be freed by the caller.
223 char *get_task_list(void)
225 struct task *t, *tmp;
230 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
232 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
236 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
238 // if (t->pre_select)
240 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
244 //PARA_DEBUG_LOG("task list:\n%s", msg);
249 * Set the select timeout to the minimal possible value.
251 * \param s Pointer to the scheduler struct.
253 * This causes the next select() call to return immediately.
255 void sched_min_delay(struct sched *s)
257 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
261 * Impose an upper bound for the timeout of the next select() call.
263 * \param to Maximal allowed timeout.
264 * \param s Pointer to the scheduler struct.
266 * If the current scheduler timeout is already smaller than \a to, this
267 * function does nothing. Otherwise the timeout for the next select() call is
268 * set to the given value.
270 * \sa sched_request_timeout_ms().
272 void sched_request_timeout(struct timeval *to, struct sched *s)
274 if (tv_diff(&s->select_timeout, to, NULL) > 0)
275 s->select_timeout = *to;
279 * Force the next select() call to return before the given amount of milliseconds.
281 * \param ms The maximal allowed timeout in milliseconds.
282 * \param s Pointer to the scheduler struct.
284 * Like sched_request_timeout() this imposes an upper bound on the timeout
285 * value for the next select() call.
287 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
291 sched_request_timeout(&tv, s);
295 * Force the next select() call to return before the given future time.
297 * \param barrier Absolute time before select() should return.
298 * \param s Pointer to the scheduler struct.
300 * If \a barrier is in the past, this function does nothing.
302 * \sa sched_request_barrier_or_min_delay().
304 void sched_request_barrier(struct timeval *barrier, struct sched *s)
308 if (tv_diff(now, barrier, &diff) > 0)
310 sched_request_timeout(&diff, s);
314 * Force the next select() call to return before the given time.
316 * \param barrier Absolute time before select() should return.
317 * \param s Pointer to the scheduler struct.
319 * If \a barrier is in the past, this function requests a minimal timeout.
321 * \sa sched_min_delay(), sched_request_barrier().
323 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
327 if (tv_diff(now, barrier, &diff) > 0)
328 return sched_min_delay(s);
329 sched_request_timeout(&diff, s);