0585162142be5238a7fa463a64f05fa192a6713d
[paraslash.git] / sched.c
1 /*
2 * Copyright (C) 2006-2013 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
54 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
55 if (t->notification != 0)
56 sched_min_delay(s);
57 if (t->pre_select)
58 t->pre_select(s, t);
59 }
60 }
61
62 //#define SCHED_DEBUG 1
63 static inline void call_post_select(struct sched *s, struct task *t)
64 {
65 #ifndef SCHED_DEBUG
66 t->post_select(s, t);
67 #else
68 struct timeval t1, t2, diff;
69 unsigned long pst;
70
71 gettimeofday(&t1, NULL);
72 t->post_select(s, t);
73 gettimeofday(&t2, NULL);
74 tv_diff(&t1, &t2, &diff);
75 pst = tv2ms(&diff);
76 if (pst > 50)
77 PARA_WARNING_LOG("%s: post_select time: %lums\n",
78 t->status, pst);
79 #endif
80 }
81
82 static void sched_post_select(struct sched *s)
83 {
84 struct task *t, *tmp;
85
86 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
87 if (t->error >= 0)
88 call_post_select(s, t);
89 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
90 t->notification = 0;
91 if (t->error >= 0)
92 continue;
93 unregister_task(t);
94 }
95 }
96
97 /**
98 * The core function for all paraslash programs.
99 *
100 * \param s Pointer to the scheduler struct.
101 *
102 * This function updates the global \a now pointer, calls all registered
103 * pre_select hooks which may set the timeout and add any file descriptors to
104 * the fd sets of \a s. Next, it calls para_select() and makes the result available
105 * to the registered tasks by calling their post_select hook.
106 *
107 * \return Zero if no more tasks are left in either of the two lists, negative
108 * if para_select returned an error.
109 *
110 * \sa task, now.
111 */
112 int schedule(struct sched *s)
113 {
114 int ret;
115
116 if (!s->select_function)
117 s->select_function = para_select;
118 again:
119 FD_ZERO(&s->rfds);
120 FD_ZERO(&s->wfds);
121 s->select_timeout = s->default_timeout;
122 s->max_fileno = -1;
123 gettimeofday(now, NULL);
124 sched_preselect(s);
125 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
126 &s->select_timeout);
127 if (ret < 0)
128 return ret;
129 if (ret == 0) {
130 /*
131 * APUE: Be careful not to check the descriptor sets on return
132 * unless the return value is greater than zero. The return
133 * state of the descriptor sets is implementation dependent if
134 * either a signal is caught or the timer expires.
135 */
136 FD_ZERO(&s->rfds);
137 FD_ZERO(&s->wfds);
138 }
139 gettimeofday(now, NULL);
140 sched_post_select(s);
141 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
142 return 0;
143 goto again;
144 }
145
146 /**
147 * Add a task to the scheduler.
148 *
149 * \param t The task to add.
150 * \param s The scheduler instance to add the task to.
151 *
152 * If the pre_select pointer of \a t is not \p NULL, it is added to
153 * the pre_select list of the scheduler. Same goes for post_select.
154 *
155 * \sa task::pre_select, task::post_select
156 */
157 void register_task(struct sched *s, struct task *t)
158 {
159 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
160 t->notification = 0;
161 if (!s->pre_select_list.next)
162 INIT_LIST_HEAD(&s->pre_select_list);
163 if (!s->post_select_list.next)
164 INIT_LIST_HEAD(&s->post_select_list);
165 if (t->pre_select) {
166 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
167 list_add_tail(&t->pre_select_node, &s->pre_select_list);
168 }
169 if (t->post_select) {
170 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
171 list_add_tail(&t->post_select_node, &s->post_select_list);
172 }
173 }
174
175 /**
176 * Get the list of all registered tasks.
177 *
178 * \param s The scheduler instance to get the task list from.
179 *
180 * \return The task list.
181 *
182 * Each entry of the list contains an identifier which is simply a hex number.
183 * The result is dynamically allocated and must be freed by the caller.
184 */
185 char *get_task_list(struct sched *s)
186 {
187 struct task *t, *tmp;
188 char *msg = NULL;
189
190 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
191 char *tmp_msg;
192 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
193 free(msg);
194 msg = tmp_msg;
195 }
196 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
197 char *tmp_msg;
198 // if (t->pre_select)
199 // continue;
200 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
201 free(msg);
202 msg = tmp_msg;
203 }
204 //PARA_DEBUG_LOG("task list:\n%s", msg);
205 return msg;
206 }
207
208 /**
209 * Set the notification value of a task.
210 *
211 * \param t The task to notify.
212 * \param err A positive error code.
213 *
214 * Tasks which honor notifications are supposed to call \ref
215 * task_get_notification() in their post_select function and act on the
216 * returned notification value.
217 *
218 * If the scheduler detects during its pre_select loop that at least one task
219 * has been notified, the loop terminates, and the post_select methods of all
220 * taks are immediately called again.
221 *
222 * The notification for a task is reset after the call to its post_select
223 * method.
224 *
225 * \sa \ref task_get_notification().
226 */
227 void task_notify(struct task *t, int err)
228 {
229 assert(err > 0);
230 if (t->notification == -err) /* ignore subsequent notifications */
231 return;
232 PARA_INFO_LOG("notifying task %s: %s\n", t->status, para_strerror(err));
233 t->notification = -err;
234 }
235
236 /**
237 * Return the notification value of a task.
238 *
239 * \param t The task to get the notification value from.
240 *
241 * \return The notification value. If this is negative, the task has been
242 * notified by another task. Tasks are supposed to check for notifications by
243 * calling this function from their post_select method.
244 *
245 * \sa \ref task_notify().
246 */
247 int task_get_notification(struct task *t)
248 {
249 return t->notification;
250 }
251
252 /**
253 * Set the notification value of all tasks of a scheduler instance.
254 *
255 * \param s The scheduler instance whose tasks should be notified.
256 * \param err A positive error code.
257 *
258 * This simply iterates over all existing tasks of \a s and sets each
259 * task's notification value to \p -err.
260 */
261 void task_notify_all(struct sched *s, int err)
262 {
263 struct task *t;
264
265 list_for_each_entry(t, &s->pre_select_list, pre_select_node)
266 task_notify(t, err);
267 list_for_each_entry(t, &s->post_select_list, post_select_node)
268 task_notify(t, err);
269 }
270
271 /**
272 * Set the select timeout to the minimal possible value.
273 *
274 * \param s Pointer to the scheduler struct.
275 *
276 * This causes the next select() call to return immediately.
277 */
278 void sched_min_delay(struct sched *s)
279 {
280 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
281 }
282
283 /**
284 * Impose an upper bound for the timeout of the next select() call.
285 *
286 * \param to Maximal allowed timeout.
287 * \param s Pointer to the scheduler struct.
288 *
289 * If the current scheduler timeout is already smaller than \a to, this
290 * function does nothing. Otherwise the timeout for the next select() call is
291 * set to the given value.
292 *
293 * \sa sched_request_timeout_ms().
294 */
295 void sched_request_timeout(struct timeval *to, struct sched *s)
296 {
297 if (tv_diff(&s->select_timeout, to, NULL) > 0)
298 s->select_timeout = *to;
299 }
300
301 /**
302 * Force the next select() call to return before the given amount of milliseconds.
303 *
304 * \param ms The maximal allowed timeout in milliseconds.
305 * \param s Pointer to the scheduler struct.
306 *
307 * Like sched_request_timeout() this imposes an upper bound on the timeout
308 * value for the next select() call.
309 */
310 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
311 {
312 struct timeval tv;
313 ms2tv(ms, &tv);
314 sched_request_timeout(&tv, s);
315 }
316
317 /**
318 * Force the next select() call to return before the given future time.
319 *
320 * \param barrier Absolute time before select() should return.
321 * \param s Pointer to the scheduler struct.
322 *
323 * \return If \a barrier is in the past, this function does nothing and returns
324 * zero. Otherwise it returns one.
325 *
326 * \sa sched_request_barrier_or_min_delay().
327 */
328 int sched_request_barrier(struct timeval *barrier, struct sched *s)
329 {
330 struct timeval diff;
331
332 if (tv_diff(now, barrier, &diff) > 0)
333 return 0;
334 sched_request_timeout(&diff, s);
335 return 1;
336 }
337
338 /**
339 * Force the next select() call to return before the given time.
340 *
341 * \param barrier Absolute time before select() should return.
342 * \param s Pointer to the scheduler struct.
343 *
344 * \return If \a barrier is in the past, this function requests a minimal
345 * timeout and returns zero. Otherwise it returns one.
346 *
347 * \sa sched_min_delay(), sched_request_barrier().
348 */
349 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
350 {
351 struct timeval diff;
352
353 if (tv_diff(now, barrier, &diff) > 0) {
354 sched_min_delay(s);
355 return 0;
356 }
357 sched_request_timeout(&diff, s);
358 return 1;
359 }