Merge branch 't/afh_receiver'
[paraslash.git] / sched.c
1 /*
2 * Copyright (C) 2006-2012 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file sched.c Paraslash's scheduling functions. */
8
9 #include <regex.h>
10 #include <assert.h>
11 #include <sys/time.h>
12
13 #include "para.h"
14 #include "ipc.h"
15 #include "fd.h"
16 #include "list.h"
17 #include "sched.h"
18 #include "string.h"
19 #include "time.h"
20 #include "error.h"
21
22 static struct timeval now_struct;
23 struct timeval *now = &now_struct;
24
25 /*
26 * Remove a task from the scheduler.
27 *
28 * \param t The task to remove.
29 *
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.
32 */
33 static void unregister_task(struct task *t)
34 {
35 assert(t->error < 0);
36 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
37 para_strerror(-t->error));
38 if (t->pre_select)
39 list_del(&t->pre_select_node);
40 if (t->post_select)
41 list_del(&t->post_select_node);
42 }
43
44 static inline bool timeout_is_zero(struct sched *s)
45 {
46 struct timeval *tv = &s->select_timeout;
47 return tv->tv_sec == 0 && tv->tv_usec == 0;
48 }
49
50 static void sched_preselect(struct sched *s)
51 {
52 struct task *t, *tmp;
53 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
54 if (t->error < 0) {
55 unregister_task(t);
56 continue;
57 }
58 if (t->notification != 0) {
59 sched_min_delay(s);
60 break;
61 }
62 if (!t->pre_select)
63 continue;
64 t->pre_select(s, t);
65 if (timeout_is_zero(s))
66 break;
67 }
68 }
69
70 //#define SCHED_DEBUG 1
71 static inline void call_post_select(struct sched *s, struct task *t)
72 {
73 #ifndef SCHED_DEBUG
74 t->post_select(s, t);
75 #else
76 struct timeval t1, t2, diff;
77 unsigned long pst;
78
79 gettimeofday(&t1, NULL);
80 t->post_select(s, t);
81 gettimeofday(&t2, NULL);
82 tv_diff(&t1, &t2, &diff);
83 pst = tv2ms(&diff);
84 if (pst > 50)
85 PARA_WARNING_LOG("%s: post_select time: %lums\n",
86 t->status, pst);
87 #endif
88 }
89
90 static void sched_post_select(struct sched *s)
91 {
92 struct task *t, *tmp;
93
94 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
95 if (t->error >= 0)
96 call_post_select(s, t);
97 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
98 t->notification = 0;
99 if (t->error >= 0)
100 continue;
101 unregister_task(t);
102 }
103 }
104
105 /**
106 * The core function for all paraslash programs.
107 *
108 * \param s Pointer to the scheduler struct.
109 *
110 * This function updates the global \a now pointer, calls all registered
111 * pre_select hooks which may set the timeout and add any file descriptors to
112 * the fd sets of \a s. Next, it calls para_select() and makes the result available
113 * to the registered tasks by calling their post_select hook.
114 *
115 * \return Zero if no more tasks are left in either of the two lists, negative
116 * if para_select returned an error.
117 *
118 * \sa task, now.
119 */
120 int schedule(struct sched *s)
121 {
122 int ret;
123
124 if (!s->select_function)
125 s->select_function = para_select;
126 again:
127 FD_ZERO(&s->rfds);
128 FD_ZERO(&s->wfds);
129 s->select_timeout = s->default_timeout;
130 s->max_fileno = -1;
131 gettimeofday(now, NULL);
132 sched_preselect(s);
133 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
134 return 0;
135 if (!timeout_is_zero(s)) {
136 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
137 &s->select_timeout);
138 if (ret < 0)
139 return ret;
140 if (ret == 0) {
141 /*
142 * APUE: Be careful not to check the descriptor sets on return
143 * unless the return value is greater than zero. The return
144 * state of the descriptor sets is implementation dependent if
145 * either a signal is caught or the timer expires.
146 */
147 FD_ZERO(&s->rfds);
148 FD_ZERO(&s->wfds);
149 }
150 gettimeofday(now, NULL);
151 } else {
152 FD_ZERO(&s->rfds);
153 FD_ZERO(&s->wfds);
154 }
155 sched_post_select(s);
156 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
157 return 0;
158 goto again;
159 }
160
161 /**
162 * Add a task to the scheduler.
163 *
164 * \param t The task to add.
165 * \param s The scheduler instance to add the task to.
166 *
167 * If the pre_select pointer of \a t is not \p NULL, it is added to
168 * the pre_select list of the scheduler. Same goes for post_select.
169 *
170 * \sa task::pre_select, task::post_select
171 */
172 void register_task(struct sched *s, struct task *t)
173 {
174 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
175 t->notification = 0;
176 if (!s->pre_select_list.next)
177 INIT_LIST_HEAD(&s->pre_select_list);
178 if (!s->post_select_list.next)
179 INIT_LIST_HEAD(&s->post_select_list);
180 if (t->pre_select) {
181 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
182 list_add_tail(&t->pre_select_node, &s->pre_select_list);
183 }
184 if (t->post_select) {
185 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
186 list_add_tail(&t->post_select_node, &s->post_select_list);
187 }
188 }
189
190 /**
191 * Get the list of all registered tasks.
192 *
193 * \param s The scheduler instance to get the task list from.
194 *
195 * \return The task list.
196 *
197 * Each entry of the list contains an identifier which is simply a hex number.
198 * The result is dynamically allocated and must be freed by the caller.
199 */
200 char *get_task_list(struct sched *s)
201 {
202 struct task *t, *tmp;
203 char *msg = NULL;
204
205 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
206 char *tmp_msg;
207 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
208 free(msg);
209 msg = tmp_msg;
210 }
211 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
212 char *tmp_msg;
213 // if (t->pre_select)
214 // continue;
215 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
216 free(msg);
217 msg = tmp_msg;
218 }
219 //PARA_DEBUG_LOG("task list:\n%s", msg);
220 return msg;
221 }
222
223 /**
224 * Set the notification value of a task.
225 *
226 * \param t The task to notify.
227 * \param err A positive error code.
228 *
229 * Tasks which honor notifications are supposed to call \ref
230 * task_get_notification() in their post_select function and act on the
231 * returned notification value.
232 *
233 * If the scheduler detects during its pre_select loop that at least one task
234 * has been notified, the loop terminates, and the post_select methods of all
235 * taks are immediately called again.
236 *
237 * The notification for a task is reset after the call to its post_select
238 * method.
239 *
240 * \sa \ref task_get_notification().
241 */
242 void task_notify(struct task *t, int err)
243 {
244 assert(err > 0);
245 if (t->notification == -err) /* ignore subsequent notifications */
246 return;
247 PARA_INFO_LOG("notifying task %s: %s\n", t->status, para_strerror(err));
248 t->notification = -err;
249 }
250
251 /**
252 * Return the notification value of a task.
253 *
254 * \param t The task to get the notification value from.
255 *
256 * \return The notification value. If this is negative, the task has been
257 * notified by another task. Tasks are supposed to check for notifications by
258 * calling this function from their post_select method.
259 *
260 * \sa \ref task_notify().
261 */
262 int task_get_notification(struct task *t)
263 {
264 return t->notification;
265 }
266
267 /**
268 * Set the notification value of all tasks of a scheduler instance.
269 *
270 * \param s The scheduler instance whose tasks should be notified.
271 * \param err A positive error code.
272 *
273 * This simply iterates over all existing tasks of \a s and sets each
274 * task's notification value to \p -err.
275 */
276 void task_notify_all(struct sched *s, int err)
277 {
278 struct task *t;
279
280 list_for_each_entry(t, &s->pre_select_list, pre_select_node)
281 task_notify(t, err);
282 list_for_each_entry(t, &s->post_select_list, post_select_node)
283 task_notify(t, err);
284 }
285
286 /**
287 * Set the select timeout to the minimal possible value.
288 *
289 * \param s Pointer to the scheduler struct.
290 *
291 * This causes the next select() call to return immediately.
292 */
293 void sched_min_delay(struct sched *s)
294 {
295 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
296 }
297
298 /**
299 * Impose an upper bound for the timeout of the next select() call.
300 *
301 * \param to Maximal allowed timeout.
302 * \param s Pointer to the scheduler struct.
303 *
304 * If the current scheduler timeout is already smaller than \a to, this
305 * function does nothing. Otherwise the timeout for the next select() call is
306 * set to the given value.
307 *
308 * \sa sched_request_timeout_ms().
309 */
310 void sched_request_timeout(struct timeval *to, struct sched *s)
311 {
312 if (tv_diff(&s->select_timeout, to, NULL) > 0)
313 s->select_timeout = *to;
314 }
315
316 /**
317 * Force the next select() call to return before the given amount of milliseconds.
318 *
319 * \param ms The maximal allowed timeout in milliseconds.
320 * \param s Pointer to the scheduler struct.
321 *
322 * Like sched_request_timeout() this imposes an upper bound on the timeout
323 * value for the next select() call.
324 */
325 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
326 {
327 struct timeval tv;
328 ms2tv(ms, &tv);
329 sched_request_timeout(&tv, s);
330 }
331
332 /**
333 * Force the next select() call to return before the given future time.
334 *
335 * \param barrier Absolute time before select() should return.
336 * \param s Pointer to the scheduler struct.
337 *
338 * \return If \a barrier is in the past, this function does nothing and returns
339 * zero. Otherwise it returns one.
340 *
341 * \sa sched_request_barrier_or_min_delay().
342 */
343 int sched_request_barrier(struct timeval *barrier, struct sched *s)
344 {
345 struct timeval diff;
346
347 if (tv_diff(now, barrier, &diff) > 0)
348 return 0;
349 sched_request_timeout(&diff, s);
350 return 1;
351 }
352
353 /**
354 * Force the next select() call to return before the given time.
355 *
356 * \param barrier Absolute time before select() should return.
357 * \param s Pointer to the scheduler struct.
358 *
359 * \return If \a barrier is in the past, this function requests a minimal
360 * timeout and returns zero. Otherwise it returns one.
361 *
362 * \sa sched_min_delay(), sched_request_barrier().
363 */
364 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
365 {
366 struct timeval diff;
367
368 if (tv_diff(now, barrier, &diff) > 0) {
369 sched_min_delay(s);
370 return 0;
371 }
372 sched_request_timeout(&diff, s);
373 return 1;
374 }