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)
41 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
42 t->error <0? para_strerror(-t->error) : "shutdown");
44 list_del(&t->pre_select_node);
46 list_del(&t->post_select_node);
47 t->error = -E_TASK_UNREGISTERED;
51 static void sched_preselect(struct sched *s)
54 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
55 if (t->error >= 0 && t->pre_select)
57 // PARA_INFO_LOG("%s \n", t->status);
61 * We have to check whether the list is empty because the call
62 * to ->pre_select() might have called sched_shutdown(). In
63 * this case t has been unregistered already, so we must not
64 * unregister it again.
66 if (list_empty(&pre_select_list))
72 //#define SCHED_DEBUG 1
73 static inline void call_post_select(struct sched *s, struct task *t)
78 struct timeval t1, t2, diff;
81 gettimeofday(&t1, NULL);
83 gettimeofday(&t2, NULL);
84 tv_diff(&t1, &t2, &diff);
87 PARA_WARNING_LOG("%s: post_select time: %lums\n",
92 static void sched_post_select(struct sched *s)
96 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
98 call_post_select(s, t);
99 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
102 /* nec., see sched_preselect() */
103 if (list_empty(&post_select_list))
110 * The core function for all paraslash programs.
112 * \param s Pointer to the scheduler struct.
114 * This function updates the global \a now pointer, calls all registered
115 * pre_select hooks which may set the timeout and add any file descriptors to
116 * the fd sets of \a s. Next, it calls para_select() and makes the result available
117 * to the registered tasks by calling their post_select hook.
119 * \return Zero if no more tasks are left in either of the two lists, negative
120 * if para_select returned an error.
124 int schedule(struct sched *s)
129 return -E_NOT_INITIALIZED;
130 if (!s->select_function)
131 s->select_function = para_select;
135 s->select_timeout = s->default_timeout;
137 gettimeofday(now, NULL);
139 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
141 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
147 * APUE: Be careful not to check the descriptor sets on return
148 * unless the return value is greater than zero. The return
149 * state of the descriptor sets is implementation dependent if
150 * either a signal is caught or the timer expires.
155 gettimeofday(now, NULL);
156 sched_post_select(s);
157 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
163 * Initialize the paraslash scheduler.
165 static void init_sched(void)
167 PARA_INFO_LOG("initializing scheduler\n");
168 INIT_LIST_HEAD(&pre_select_list);
169 INIT_LIST_HEAD(&post_select_list);
174 * Add a task to the scheduler.
176 * \param t the task to add
178 * If the pre_select pointer of \a t is not \p NULL, it is added to
179 * the pre_select list of the scheduler. Same goes for post_select.
181 * \sa task::pre_select, task::post_select
183 void register_task(struct task *t)
187 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
189 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
190 list_add_tail(&t->pre_select_node, &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, &post_select_list);
199 * Unregister all tasks.
201 * This will cause \a schedule() to return immediately because both the
202 * \a pre_select_list and the \a post_select_list are empty.
204 void sched_shutdown(void)
206 struct task *t, *tmp;
210 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
212 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
218 * Get the list of all registered tasks.
220 * \return The task list.
222 * Each entry of the list contains an identifier which is simply a hex number
223 * that may be used in \a kill_task() to terminate the task.
224 * The result is dynamically allocated and must be freed by the caller.
226 char *get_task_list(void)
228 struct task *t, *tmp;
233 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
235 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
239 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
241 // if (t->pre_select)
243 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
247 //PARA_DEBUG_LOG("task list:\n%s", msg);
252 * Simulate an error for the given task.
254 * \param id The task identifier.
256 * Find the task identified by \a id, set the tasks' error value to
257 * \p -E_TASK_KILLED and unregister the task.
259 * \return Positive on success, negative on errors (e.g. if \a id does not
260 * correspond to a registered task).
262 int kill_task(char *id)
264 struct task *t, *tmp;
268 return -E_NOT_INITIALIZED;
269 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
270 sprintf(buf, "%p", t);
273 t->error = -E_TASK_KILLED;
276 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
277 sprintf(buf, "%p", t);
280 t->error = -E_TASK_KILLED;
283 return -E_NO_SUCH_TASK;
287 * Set the select timeout to the minimal possible value.
289 * \param s Pointer to the scheduler struct.
291 * This causes the next select() call to return immediately.
293 void sched_min_delay(struct sched *s)
295 s->select_timeout.tv_sec = 0;
296 s->select_timeout.tv_usec = 1;
300 * Impose an upper bound for the timeout of the next select() call.
302 * \param to Maximal allowed timeout.
303 * \param s Pointer to the scheduler struct.
305 * If the current scheduler timeout is already smaller than \a to, this
306 * function does nothing. Otherwise the timeout for the next select() call is
307 * set to the given value.
309 * \sa sched_request_timeout_ms().
311 void sched_request_timeout(struct timeval *to, struct sched *s)
313 if (tv_diff(&s->select_timeout, to, NULL) > 0)
314 s->select_timeout = *to;
318 * Force the next select() call to return before the given amount of milliseconds.
320 * \param ms The maximal allowed timeout in milliseconds.
321 * \param s Pointer to the scheduler struct.
323 * Like sched_request_timeout() this imposes an upper bound on the timeout
324 * value for the next select() call.
326 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
330 sched_request_timeout(&tv, s);
334 * Force the next select() call to return before the given future time.
336 * \param barrier Absolute time before select() should return.
337 * \param s Pointer to the scheduler struct.
339 * If \a barrier is in the past, this function does nothing.
341 * \sa sched_request_barrier_or_min_delay().
343 void sched_request_barrier(struct timeval *barrier, struct sched *s)
347 if (tv_diff(now, barrier, &diff) > 0)
349 sched_request_timeout(&diff, s);
353 * Force the next select() call to return before the given time.
355 * \param barrier Absolute time before select() should return.
356 * \param s Pointer to the scheduler struct.
358 * If \a barrier is in the past, this function requests a minimal timeout.
360 * \sa sched_min_delay(), sched_request_barrier().
362 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
366 if (tv_diff(now, barrier, &diff) > 0)
367 return sched_min_delay(s);
368 sched_request_timeout(&diff, s);