2 * Copyright (C) 2006-2012 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 timeval now_struct
;
23 struct timeval
*now
= &now_struct
;
26 * Remove a task from the scheduler.
28 * \param t The task to remove.
30 * If the pre_select pointer of \a t is not \p NULL, it is removed from
31 * the pre_select list of the scheduler. Same goes for \a post_select.
33 static void unregister_task(struct task
*t
)
36 PARA_INFO_LOG("unregistering %s (%s)\n", t
->status
,
37 para_strerror(-t
->error
));
39 list_del(&t
->pre_select_node
);
41 list_del(&t
->post_select_node
);
44 static inline bool timeout_is_zero(struct sched
*s
)
46 struct timeval
*tv
= &s
->select_timeout
;
47 return tv
->tv_sec
== 0 && tv
->tv_usec
== 0;
50 static void sched_preselect(struct sched
*s
)
53 list_for_each_entry_safe(t
, tmp
, &s
->pre_select_list
, pre_select_node
) {
58 if (t
->notification
!= 0) {
65 if (timeout_is_zero(s
))
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
, &s
->post_select_list
, post_select_node
) {
96 call_post_select(s
, t
);
97 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
102 * We have to check whether the list is empty because the call
103 * to ->post_select() might have called sched_shutdown(). In
104 * this case t has been unregistered already, so we must not
105 * unregister it again.
107 if (list_empty(&s
->post_select_list
))
114 * The core function for all paraslash programs.
116 * \param s Pointer to the scheduler struct.
118 * This function updates the global \a now pointer, calls all registered
119 * pre_select hooks which may set the timeout and add any file descriptors to
120 * the fd sets of \a s. Next, it calls para_select() and makes the result available
121 * to the registered tasks by calling their post_select hook.
123 * \return Zero if no more tasks are left in either of the two lists, negative
124 * if para_select returned an error.
128 int schedule(struct sched
*s
)
132 if (!s
->select_function
)
133 s
->select_function
= para_select
;
137 s
->select_timeout
= s
->default_timeout
;
139 gettimeofday(now
, NULL
);
141 if (list_empty(&s
->pre_select_list
) && list_empty(&s
->post_select_list
))
143 if (!timeout_is_zero(s
)) {
144 ret
= s
->select_function(s
->max_fileno
+ 1, &s
->rfds
, &s
->wfds
,
150 * APUE: Be careful not to check the descriptor sets on return
151 * unless the return value is greater than zero. The return
152 * state of the descriptor sets is implementation dependent if
153 * either a signal is caught or the timer expires.
158 gettimeofday(now
, NULL
);
163 sched_post_select(s
);
164 if (list_empty(&s
->pre_select_list
) && list_empty(&s
->post_select_list
))
170 * Add a task to the scheduler.
172 * \param t The task to add.
173 * \param s The scheduler instance to add the task to.
175 * If the pre_select pointer of \a t is not \p NULL, it is added to
176 * the pre_select list of the scheduler. Same goes for post_select.
178 * \sa task::pre_select, task::post_select
180 void register_task(struct sched
*s
, struct task
*t
)
182 PARA_INFO_LOG("registering %s (%p)\n", t
->status
, t
);
184 if (!s
->pre_select_list
.next
)
185 INIT_LIST_HEAD(&s
->pre_select_list
);
186 if (!s
->post_select_list
.next
)
187 INIT_LIST_HEAD(&s
->post_select_list
);
189 PARA_DEBUG_LOG("pre_select: %p\n", &t
->pre_select
);
190 list_add_tail(&t
->pre_select_node
, &s
->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
, &s
->post_select_list
);
199 * Unregister all tasks.
201 * \param s The scheduler instance to shut down.
203 * This will cause \a schedule() to return immediately because both the
204 * \a pre_select_list and the \a post_select_list are empty. This function
205 * must be called from the post_select (rather than the pre_select) method.
207 void sched_shutdown(struct sched
*s
)
209 struct task
*t
, *tmp
;
211 list_for_each_entry_safe(t
, tmp
, &s
->pre_select_list
, pre_select_node
) {
212 t
->error
= -E_SCHED_SHUTDOWN
;
215 list_for_each_entry_safe(t
, tmp
, &s
->post_select_list
, post_select_node
) {
216 t
->error
= -E_SCHED_SHUTDOWN
;
222 * Get the list of all registered tasks.
224 * \param s The scheduler instance to get the task list from.
226 * \return The task list.
228 * Each entry of the list contains an identifier which is simply a hex number.
229 * The result is dynamically allocated and must be freed by the caller.
231 char *get_task_list(struct sched
*s
)
233 struct task
*t
, *tmp
;
236 list_for_each_entry_safe(t
, tmp
, &s
->pre_select_list
, pre_select_node
) {
238 tmp_msg
= make_message("%s%p\tpre\t%s\n", msg
? msg
: "", t
, t
->status
);
242 list_for_each_entry_safe(t
, tmp
, &s
->post_select_list
, post_select_node
) {
244 // if (t->pre_select)
246 tmp_msg
= make_message("%s%p\tpost\t%s\n", msg
? msg
: "", t
, t
->status
);
250 //PARA_DEBUG_LOG("task list:\n%s", msg);
255 * Set the notification value of a task.
257 * \param t The task to notify.
258 * \param err A positive error code.
260 * Tasks which honor notifications are supposed to call \ref
261 * task_get_notification() in their post_select function and act on the
262 * returned notification value.
264 * If the scheduler detects during its pre_select loop that at least one task
265 * has been notified, the loop terminates, and the post_select methods of all
266 * taks are immediately called again.
268 * The notification for a task is reset after the call to its post_select
271 * \sa \ref task_get_notification().
273 void task_notify(struct task
*t
, int err
)
276 if (t
->notification
== -err
) /* ignore subsequent notifications */
278 PARA_INFO_LOG("notifying task %s: %s\n", t
->status
, para_strerror(err
));
279 t
->notification
= -err
;
283 * Return the notification value of a task.
285 * \param t The task to get the notification value from.
287 * \return The notification value. If this is negative, the task has been
288 * notified by another task. Tasks are supposed to check for notifications by
289 * calling this function from their post_select method.
291 * \sa \ref task_notify().
293 int task_get_notification(struct task
*t
)
295 return t
->notification
;
299 * Set the select timeout to the minimal possible value.
301 * \param s Pointer to the scheduler struct.
303 * This causes the next select() call to return immediately.
305 void sched_min_delay(struct sched
*s
)
307 s
->select_timeout
.tv_sec
= s
->select_timeout
.tv_usec
= 0;
311 * Impose an upper bound for the timeout of the next select() call.
313 * \param to Maximal allowed timeout.
314 * \param s Pointer to the scheduler struct.
316 * If the current scheduler timeout is already smaller than \a to, this
317 * function does nothing. Otherwise the timeout for the next select() call is
318 * set to the given value.
320 * \sa sched_request_timeout_ms().
322 void sched_request_timeout(struct timeval
*to
, struct sched
*s
)
324 if (tv_diff(&s
->select_timeout
, to
, NULL
) > 0)
325 s
->select_timeout
= *to
;
329 * Force the next select() call to return before the given amount of milliseconds.
331 * \param ms The maximal allowed timeout in milliseconds.
332 * \param s Pointer to the scheduler struct.
334 * Like sched_request_timeout() this imposes an upper bound on the timeout
335 * value for the next select() call.
337 void sched_request_timeout_ms(long unsigned ms
, struct sched
*s
)
341 sched_request_timeout(&tv
, s
);
345 * Force the next select() call to return before the given future time.
347 * \param barrier Absolute time before select() should return.
348 * \param s Pointer to the scheduler struct.
350 * \return If \a barrier is in the past, this function does nothing and returns
351 * zero. Otherwise it returns one.
353 * \sa sched_request_barrier_or_min_delay().
355 int sched_request_barrier(struct timeval
*barrier
, struct sched
*s
)
359 if (tv_diff(now
, barrier
, &diff
) > 0)
361 sched_request_timeout(&diff
, s
);
366 * Force the next select() call to return before the given time.
368 * \param barrier Absolute time before select() should return.
369 * \param s Pointer to the scheduler struct.
371 * \return If \a barrier is in the past, this function requests a minimal
372 * timeout and returns zero. Otherwise it returns one.
374 * \sa sched_min_delay(), sched_request_barrier().
376 int sched_request_barrier_or_min_delay(struct timeval
*barrier
, struct sched
*s
)
380 if (tv_diff(now
, barrier
, &diff
) > 0) {
384 sched_request_timeout(&diff
, s
);