sched: Fix SCHED_DEBUG.
[paraslash.git] / sched.c
1 /*
2 * Copyright (C) 2006-2010 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 <dirent.h> /* readdir() */
11 #include <assert.h>
12 #include <sys/time.h>
13
14 #include "para.h"
15 #include "ipc.h"
16 #include "fd.h"
17 #include "list.h"
18 #include "sched.h"
19 #include "string.h"
20 #include "time.h"
21 #include "error.h"
22
23 static struct list_head pre_select_list, post_select_list;
24 static int initialized;
25
26 static struct timeval now_struct;
27 struct timeval *now = &now_struct;
28
29 /*
30 * Remove a task from the scheduler.
31 *
32 * \param t The task to remove.
33 *
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.
36 */
37 static void unregister_task(struct task *t)
38 {
39 if (!initialized)
40 return;
41 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
42 t->error <0? para_strerror(-t->error) : "shutdown");
43 if (t->pre_select)
44 list_del(&t->pre_select_node);
45 if (t->post_select)
46 list_del(&t->post_select_node);
47 t->error = -E_TASK_UNREGISTERED;
48 }
49
50
51 static void sched_preselect(struct sched *s)
52 {
53 struct task *t, *tmp;
54 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
55 if (t->error >= 0 && t->pre_select)
56 t->pre_select(s, t);
57 // PARA_INFO_LOG("%s \n", t->status);
58 if (t->error >= 0)
59 continue;
60 /*
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.
65 */
66 if (list_empty(&pre_select_list))
67 return;
68 unregister_task(t);
69 }
70 }
71
72 //#define SCHED_DEBUG 1
73 static inline void call_post_select(struct sched *s, struct task *t)
74 {
75 #ifndef SCHED_DEBUG
76 t->post_select(s, t);
77 #else
78 struct timeval t1, t2, diff;
79 unsigned long pst;
80
81 gettimeofday(&t1, NULL);
82 t->post_select(s, t);
83 gettimeofday(&t2, NULL);
84 tv_diff(&t1, &t2, &diff);
85 pst = tv2ms(&diff);
86 if (pst > 50)
87 PARA_WARNING_LOG("%s: post_select time: %lums\n",
88 t->status, pst);
89 #endif
90 }
91
92 static void sched_post_select(struct sched *s)
93 {
94 struct task *t, *tmp;
95
96 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
97 if (t->error >= 0)
98 call_post_select(s, t);
99 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
100 if (t->error >= 0)
101 continue;
102 /* nec., see sched_preselect() */
103 if (list_empty(&post_select_list))
104 return;
105 unregister_task(t);
106 }
107 }
108
109 /**
110 * The core function for all paraslash programs.
111 *
112 * \param s Pointer to the scheduler struct.
113 *
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.
118 *
119 * \return Zero if no more tasks are left in either of the two lists, negative
120 * if para_select returned an error.
121 *
122 * \sa task, now.
123 */
124 int schedule(struct sched *s)
125 {
126 int ret;
127
128 if (!initialized)
129 return -E_NOT_INITIALIZED;
130 if (!s->select_function)
131 s->select_function = para_select;
132 again:
133 FD_ZERO(&s->rfds);
134 FD_ZERO(&s->wfds);
135 s->timeout = s->default_timeout;
136 s->max_fileno = -1;
137 gettimeofday(now, NULL);
138 sched_preselect(s);
139 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
140 return 0;
141 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
142 if (ret < 0)
143 return ret;
144 if (ret == 0) {
145 /*
146 * APUE: Be careful not to check the descriptor sets on return
147 * unless the return value is greater than zero. The return
148 * state of the descriptor sets is implementation dependent if
149 * either a signal is caught or the timer expires.
150 */
151 FD_ZERO(&s->rfds);
152 FD_ZERO(&s->wfds);
153 }
154 gettimeofday(now, NULL);
155 sched_post_select(s);
156 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
157 return 0;
158 goto again;
159 }
160
161 /*
162 * Initialize the paraslash scheduler.
163 */
164 static void init_sched(void)
165 {
166 PARA_INFO_LOG("initializing scheduler\n");
167 INIT_LIST_HEAD(&pre_select_list);
168 INIT_LIST_HEAD(&post_select_list);
169 initialized = 1;
170 }
171
172 /**
173 * Add a task to the scheduler.
174 *
175 * \param t the task to add
176 *
177 * If the pre_select pointer of \a t is not \p NULL, it is added to
178 * the pre_select list of the scheduler. Same goes for post_select.
179 *
180 * \sa task::pre_select, task::post_select
181 */
182 void register_task(struct task *t)
183 {
184 if (!initialized)
185 init_sched();
186 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
187 if (t->pre_select) {
188 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
189 list_add_tail(&t->pre_select_node, &pre_select_list);
190 }
191 if (t->post_select) {
192 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
193 list_add_tail(&t->post_select_node, &post_select_list);
194 }
195 }
196
197 /**
198 * Unregister all tasks.
199 *
200 * This will cause \a schedule() to return immediately because both the
201 * \a pre_select_list and the \a post_select_list are empty.
202 */
203 void sched_shutdown(void)
204 {
205 struct task *t, *tmp;
206
207 if (!initialized)
208 return;
209 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
210 unregister_task(t);
211 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
212 unregister_task(t);
213 initialized = 0;
214 }
215
216 /**
217 * Get the list of all registered tasks.
218 *
219 * \return The task list.
220 *
221 * Each entry of the list contains an identifier which is simply a hex number
222 * that may be used in \a kill_task() to terminate the task.
223 * The result is dynamically allocated and must be freed by the caller.
224 */
225 char *get_task_list(void)
226 {
227 struct task *t, *tmp;
228 char *msg = NULL;
229
230 if (!initialized)
231 return NULL;
232 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
233 char *tmp_msg;
234 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
235 free(msg);
236 msg = tmp_msg;
237 }
238 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
239 char *tmp_msg;
240 // if (t->pre_select)
241 // continue;
242 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
243 free(msg);
244 msg = tmp_msg;
245 }
246 //PARA_DEBUG_LOG("task list:\n%s", msg);
247 return msg;
248 }
249
250 /**
251 * Simulate an error for the given task.
252 *
253 * \param id The task identifier.
254 *
255 * Find the task identified by \a id, set the tasks' error value to
256 * \p -E_TASK_KILLED and unregister the task.
257 *
258 * \return Positive on success, negative on errors (e.g. if \a id does not
259 * correspond to a registered task).
260 */
261 int kill_task(char *id)
262 {
263 struct task *t, *tmp;
264 char buf[20];
265
266 if (!initialized)
267 return -E_NOT_INITIALIZED;
268 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
269 sprintf(buf, "%p", t);
270 if (strcmp(id, buf))
271 continue;
272 t->error = -E_TASK_KILLED;
273 return 1;
274 }
275 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
276 sprintf(buf, "%p", t);
277 if (strcmp(id, buf))
278 continue;
279 t->error = -E_TASK_KILLED;
280 return 1;
281 }
282 return -E_NO_SUCH_TASK;
283 }
284
285 /**
286 * Set the select timeout to the minimal possible value.
287 *
288 * \param s Pointer to the scheduler struct.
289 *
290 * This causes the next select() call to return immediately.
291 */
292 void sched_min_delay(struct sched *s)
293 {
294 s->timeout.tv_sec = 0;
295 s->timeout.tv_usec = 1;
296 }
297
298 /**
299 * Impose an upper bound for the timeout of the next select() call.
300 *
301 * \param timeout Maximal allowed timeout.
302 * \param s Pointer to the scheduler struct.
303 *
304 * If the current scheduler timeout is already smaller than \a timeout, 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 *timeout, struct sched *s)
311 {
312 if (tv_diff(&s->timeout, timeout, NULL) > 0)
313 s->timeout = *timeout;
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 * If \a barrier is in the past, this function does nothing.
339 *
340 * \sa sched_request_barrier_or_min_delay().
341 */
342 void sched_request_barrier(struct timeval *barrier, struct sched *s)
343 {
344 struct timeval diff;
345
346 if (tv_diff(now, barrier, &diff) > 0)
347 return;
348 sched_request_timeout(&diff, s);
349 }
350
351 /**
352 * Force the next select() call to return before the given time.
353 *
354 * \param barrier Absolute time before select() should return.
355 * \param s Pointer to the scheduler struct.
356 *
357 * If \a barrier is in the past, this function requests a minimal timeout.
358 *
359 * \sa sched_min_delay(), sched_request_barrier().
360 */
361 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
362 {
363 struct timeval diff;
364
365 if (tv_diff(now, barrier, &diff) > 0)
366 return sched_min_delay(s);
367 sched_request_timeout(&diff, s);
368 }