Merge branch 't/gvf'
[paraslash.git] / sched.c
1 /*
2 * Copyright (C) 2006-2011 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 assert(t->error < 0);
42 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
43 para_strerror(-t->error));
44 if (t->pre_select)
45 list_del(&t->pre_select_node);
46 if (t->post_select)
47 list_del(&t->post_select_node);
48 }
49
50 static void sched_preselect(struct sched *s)
51 {
52 struct task *t, *tmp;
53 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
54 if (t->pre_select)
55 t->pre_select(s, t);
56 // PARA_INFO_LOG("%s \n", t->status);
57 if (t->error >= 0)
58 continue;
59 /*
60 * We have to check whether the list is empty because the call
61 * to ->pre_select() might have called sched_shutdown(). In
62 * this case t has been unregistered already, so we must not
63 * unregister it again.
64 */
65 if (list_empty(&pre_select_list))
66 return;
67 unregister_task(t);
68 }
69 }
70
71 //#define SCHED_DEBUG 1
72 static inline void call_post_select(struct sched *s, struct task *t)
73 {
74 #ifndef SCHED_DEBUG
75 t->post_select(s, t);
76 #else
77 struct timeval t1, t2, diff;
78 unsigned long pst;
79
80 gettimeofday(&t1, NULL);
81 t->post_select(s, t);
82 gettimeofday(&t2, NULL);
83 tv_diff(&t1, &t2, &diff);
84 pst = tv2ms(&diff);
85 if (pst > 50)
86 PARA_WARNING_LOG("%s: post_select time: %lums\n",
87 t->status, pst);
88 #endif
89 }
90
91 static void sched_post_select(struct sched *s)
92 {
93 struct task *t, *tmp;
94
95 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
96 if (t->error >= 0)
97 call_post_select(s, t);
98 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
99 if (t->error >= 0)
100 continue;
101 /* nec., see sched_preselect() */
102 if (list_empty(&post_select_list))
103 return;
104 unregister_task(t);
105 }
106 }
107
108 /**
109 * The core function for all paraslash programs.
110 *
111 * \param s Pointer to the scheduler struct.
112 *
113 * This function updates the global \a now pointer, calls all registered
114 * pre_select hooks which may set the timeout and add any file descriptors to
115 * the fd sets of \a s. Next, it calls para_select() and makes the result available
116 * to the registered tasks by calling their post_select hook.
117 *
118 * \return Zero if no more tasks are left in either of the two lists, negative
119 * if para_select returned an error.
120 *
121 * \sa task, now.
122 */
123 int schedule(struct sched *s)
124 {
125 int ret;
126
127 if (!initialized)
128 return -E_NOT_INITIALIZED;
129 if (!s->select_function)
130 s->select_function = para_select;
131 again:
132 FD_ZERO(&s->rfds);
133 FD_ZERO(&s->wfds);
134 s->select_timeout = s->default_timeout;
135 s->max_fileno = -1;
136 gettimeofday(now, NULL);
137 sched_preselect(s);
138 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
139 return 0;
140 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
141 &s->select_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 t->error = -E_SCHED_SHUTDOWN;
211 unregister_task(t);
212 }
213 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
214 t->error = -E_SCHED_SHUTDOWN;
215 unregister_task(t);
216 }
217 initialized = 0;
218 }
219
220 /**
221 * Get the list of all registered tasks.
222 *
223 * \return The task list.
224 *
225 * Each entry of the list contains an identifier which is simply a hex number.
226 * The result is dynamically allocated and must be freed by the caller.
227 */
228 char *get_task_list(void)
229 {
230 struct task *t, *tmp;
231 char *msg = NULL;
232
233 if (!initialized)
234 return NULL;
235 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
236 char *tmp_msg;
237 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
238 free(msg);
239 msg = tmp_msg;
240 }
241 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
242 char *tmp_msg;
243 // if (t->pre_select)
244 // continue;
245 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
246 free(msg);
247 msg = tmp_msg;
248 }
249 //PARA_DEBUG_LOG("task list:\n%s", msg);
250 return msg;
251 }
252
253 /**
254 * Set the select timeout to the minimal possible value.
255 *
256 * \param s Pointer to the scheduler struct.
257 *
258 * This causes the next select() call to return immediately.
259 */
260 void sched_min_delay(struct sched *s)
261 {
262 s->select_timeout.tv_sec = 0;
263 s->select_timeout.tv_usec = 1;
264 }
265
266 /**
267 * Impose an upper bound for the timeout of the next select() call.
268 *
269 * \param to Maximal allowed timeout.
270 * \param s Pointer to the scheduler struct.
271 *
272 * If the current scheduler timeout is already smaller than \a to, this
273 * function does nothing. Otherwise the timeout for the next select() call is
274 * set to the given value.
275 *
276 * \sa sched_request_timeout_ms().
277 */
278 void sched_request_timeout(struct timeval *to, struct sched *s)
279 {
280 if (tv_diff(&s->select_timeout, to, NULL) > 0)
281 s->select_timeout = *to;
282 }
283
284 /**
285 * Force the next select() call to return before the given amount of milliseconds.
286 *
287 * \param ms The maximal allowed timeout in milliseconds.
288 * \param s Pointer to the scheduler struct.
289 *
290 * Like sched_request_timeout() this imposes an upper bound on the timeout
291 * value for the next select() call.
292 */
293 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
294 {
295 struct timeval tv;
296 ms2tv(ms, &tv);
297 sched_request_timeout(&tv, s);
298 }
299
300 /**
301 * Force the next select() call to return before the given future time.
302 *
303 * \param barrier Absolute time before select() should return.
304 * \param s Pointer to the scheduler struct.
305 *
306 * If \a barrier is in the past, this function does nothing.
307 *
308 * \sa sched_request_barrier_or_min_delay().
309 */
310 void sched_request_barrier(struct timeval *barrier, struct sched *s)
311 {
312 struct timeval diff;
313
314 if (tv_diff(now, barrier, &diff) > 0)
315 return;
316 sched_request_timeout(&diff, s);
317 }
318
319 /**
320 * Force the next select() call to return before the given time.
321 *
322 * \param barrier Absolute time before select() should return.
323 * \param s Pointer to the scheduler struct.
324 *
325 * If \a barrier is in the past, this function requests a minimal timeout.
326 *
327 * \sa sched_min_delay(), sched_request_barrier().
328 */
329 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
330 {
331 struct timeval diff;
332
333 if (tv_diff(now, barrier, &diff) > 0)
334 return sched_min_delay(s);
335 sched_request_timeout(&diff, s);
336 }