2 * Copyright (C) 2006-2009 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() */
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)
40 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
41 t->error <0? para_strerror(-t->error) : "shutdown");
43 list_del(&t->pre_select_node);
45 list_del(&t->post_select_node);
46 t->error = -E_TASK_UNREGISTERED;
50 static void sched_preselect(struct sched *s)
53 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
54 if (t->error >= 0 && t->pre_select)
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 static void sched_post_select(struct sched *s)
75 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
78 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
81 /* nec., see sched_preselect() */
82 if (list_empty(&post_select_list))
89 * The core function for all paraslash programs.
91 * \param s Pointer to the scheduler struct.
93 * This function updates the global \a now pointer, calls all registered
94 * pre_select hooks which may set the timeout and add any file descriptors to
95 * the fd sets of \a s. Next, it calls para_select() and makes the result available
96 * to the registered tasks by calling their post_select hook.
98 * \return Zero if no more tasks are left in either of the two lists, negative
99 * if para_select returned an error.
103 int schedule(struct sched *s)
108 return -E_NOT_INITIALIZED;
109 if (!s->select_function)
110 s->select_function = para_select;
114 s->timeout = s->default_timeout;
116 gettimeofday(now, NULL);
118 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
120 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
125 * APUE: Be careful not to check the descriptor sets on return
126 * unless the return value is greater than zero. The return
127 * state of the descriptor sets is implementation dependent if
128 * either a signal is caught or the timer expires.
133 gettimeofday(now, NULL);
134 sched_post_select(s);
135 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
141 * Initialize the paraslash scheduler.
143 static void init_sched(void)
145 PARA_INFO_LOG("initializing scheduler\n");
146 INIT_LIST_HEAD(&pre_select_list);
147 INIT_LIST_HEAD(&post_select_list);
152 * Add a task to the scheduler.
154 * \param t the task to add
156 * If the pre_select pointer of \a t is not \p NULL, it is added to
157 * the pre_select list of the scheduler. Same goes for post_select.
159 * \sa task::pre_select, task::post_select
161 void register_task(struct task *t)
165 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
167 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
168 list_add_tail(&t->pre_select_node, &pre_select_list);
170 if (t->post_select) {
171 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
172 list_add_tail(&t->post_select_node, &post_select_list);
177 * Unregister all tasks.
179 * This will cause \a schedule() to return immediately because both the
180 * \a pre_select_list and the \a post_select_list are empty.
182 void sched_shutdown(void)
184 struct task *t, *tmp;
188 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
190 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
196 * Get the list of all registered tasks.
198 * \return The task list.
200 * Each entry of the list contains an identifier which is simply a hex number
201 * that may be used in \a kill_task() to terminate the task.
202 * The result is dynamically allocated and must be freed by the caller.
204 char *get_task_list(void)
206 struct task *t, *tmp;
211 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
213 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
217 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
219 // if (t->pre_select)
221 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
225 //PARA_DEBUG_LOG("task list:\n%s", msg);
230 * Simulate an error for the given task.
232 * \param id The task identifier.
234 * Find the task identified by \a id, set the tasks' error value to
235 * \p -E_TASK_KILLED and unregister the task.
237 * \return Positive on success, negative on errors (e.g. if \a id does not
238 * correspond to a registered task).
240 int kill_task(char *id)
242 struct task *t, *tmp;
246 return -E_NOT_INITIALIZED;
247 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
248 sprintf(buf, "%p", t);
251 t->error = -E_TASK_KILLED;
254 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
255 sprintf(buf, "%p", t);
258 t->error = -E_TASK_KILLED;
261 return -E_NO_SUCH_TASK;
265 * Set the select timeout to the minimal possible value.
267 * \param s Pointer to the scheduler struct.
269 * This causes the next select() call to return immediately.
271 void sched_min_delay(struct sched *s)
273 s->timeout.tv_sec = 0;
274 s->timeout.tv_usec = 1;
278 * Impose an upper bound for the timeout of the next select() call.
280 * \param timeout Maximal allowed timeout.
281 * \param s Pointer to the scheduler struct.
283 * If the current scheduler timeout is already smaller than \a timeout, this
284 * function does nothing. Otherwise the timeout for the next select() call is
285 * set to the given value.
287 * \sa sched_request_timeout_ms().
289 void sched_request_timeout(struct timeval *timeout, struct sched *s)
291 if (tv_diff(&s->timeout, timeout, NULL) > 0)
292 s->timeout = *timeout;
296 * Force the next select() call to return before the given amount of milliseconds.
298 * \param ms The maximal allowed timeout in milliseconds.
299 * \param s Pointer to the scheduler struct.
301 * Like sched_request_timeout() this imposes an upper bound on the timeout
302 * value for the next select() call.
304 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
308 sched_request_timeout(&tv, s);
312 * Force the next select() call to return before the given future time.
314 * \param barrier Absolute time before select() should return.
315 * \param s Pointer to the scheduler struct.
317 * If \a barrier is in the past, this function does nothing.
319 * \sa sched_request_barrier_or_min_delay().
321 void sched_request_barrier(struct timeval *barrier, struct sched *s)
325 if (tv_diff(now, barrier, &diff) > 0)
327 sched_request_timeout(&diff, s);
331 * Force the next select() call to return before the given time.
333 * \param barrier Absolute time before select() should return.
334 * \param s Pointer to the scheduler struct.
336 * If \a barrier is in the past, this function requests a minimal timeout.
338 * \sa sched_min_delay(), sched_request_barrier().
340 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
344 if (tv_diff(now, barrier, &diff) > 0)
345 return sched_min_delay(s);
346 sched_request_timeout(&diff, s);