Merge branch 't/interactive'
[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 <assert.h>
11 #include <sys/time.h>
12 #include <stdbool.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 timeval now_struct;
24 struct timeval *now = &now_struct;
25
26 /*
27 * Remove a task from the scheduler.
28 *
29 * \param t The task to remove.
30 *
31 * If the pre_select pointer of \a t is not \p NULL, it is removed from
32 * the pre_select list of the scheduler. Same goes for \a post_select.
33 */
34 static void unregister_task(struct task *t)
35 {
36 assert(t->error < 0);
37 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
38 para_strerror(-t->error));
39 if (t->pre_select)
40 list_del(&t->pre_select_node);
41 if (t->post_select)
42 list_del(&t->post_select_node);
43 }
44
45 static inline bool timeout_is_zero(struct sched *s)
46 {
47 struct timeval *tv = &s->select_timeout;
48 return tv->tv_sec == 0 && tv->tv_usec == 0;
49 }
50
51 static void sched_preselect(struct sched *s)
52 {
53 struct task *t, *tmp;
54 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
55 if (t->error < 0) {
56 unregister_task(t);
57 continue;
58 }
59 if (!t->pre_select)
60 continue;
61 t->pre_select(s, t);
62 if (timeout_is_zero(s))
63 break;
64 }
65 }
66
67 //#define SCHED_DEBUG 1
68 static inline void call_post_select(struct sched *s, struct task *t)
69 {
70 #ifndef SCHED_DEBUG
71 t->post_select(s, t);
72 #else
73 struct timeval t1, t2, diff;
74 unsigned long pst;
75
76 gettimeofday(&t1, NULL);
77 t->post_select(s, t);
78 gettimeofday(&t2, NULL);
79 tv_diff(&t1, &t2, &diff);
80 pst = tv2ms(&diff);
81 if (pst > 50)
82 PARA_WARNING_LOG("%s: post_select time: %lums\n",
83 t->status, pst);
84 #endif
85 }
86
87 static void sched_post_select(struct sched *s)
88 {
89 struct task *t, *tmp;
90
91 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
92 if (t->error >= 0)
93 call_post_select(s, t);
94 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
95 if (t->error >= 0)
96 continue;
97 /*
98 * We have to check whether the list is empty because the call
99 * to ->post_select() might have called sched_shutdown(). In
100 * this case t has been unregistered already, so we must not
101 * unregister it again.
102 */
103 if (list_empty(&s->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 (!s->select_function)
129 s->select_function = para_select;
130 again:
131 FD_ZERO(&s->rfds);
132 FD_ZERO(&s->wfds);
133 s->select_timeout = s->default_timeout;
134 s->max_fileno = -1;
135 gettimeofday(now, NULL);
136 sched_preselect(s);
137 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
138 return 0;
139 if (!timeout_is_zero(s)) {
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 } else {
156 FD_ZERO(&s->rfds);
157 FD_ZERO(&s->wfds);
158 }
159 sched_post_select(s);
160 if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list))
161 return 0;
162 goto again;
163 }
164
165 /**
166 * Add a task to the scheduler.
167 *
168 * \param t The task to add.
169 * \param s The scheduler instance to add the task to.
170 *
171 * If the pre_select pointer of \a t is not \p NULL, it is added to
172 * the pre_select list of the scheduler. Same goes for post_select.
173 *
174 * \sa task::pre_select, task::post_select
175 */
176 void register_task(struct sched *s, struct task *t)
177 {
178 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
179 if (!s->pre_select_list.next)
180 INIT_LIST_HEAD(&s->pre_select_list);
181 if (!s->post_select_list.next)
182 INIT_LIST_HEAD(&s->post_select_list);
183 if (t->pre_select) {
184 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
185 list_add_tail(&t->pre_select_node, &s->pre_select_list);
186 }
187 if (t->post_select) {
188 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
189 list_add_tail(&t->post_select_node, &s->post_select_list);
190 }
191 }
192
193 /**
194 * Unregister all tasks.
195 *
196 * This will cause \a schedule() to return immediately because both the
197 * \a pre_select_list and the \a post_select_list are empty. This function
198 * must be called from the post_select (rather than the pre_select) method.
199 */
200 void sched_shutdown(struct sched *s)
201 {
202 struct task *t, *tmp;
203
204 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
205 t->error = -E_SCHED_SHUTDOWN;
206 unregister_task(t);
207 }
208 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
209 t->error = -E_SCHED_SHUTDOWN;
210 unregister_task(t);
211 }
212 }
213
214 /**
215 * Get the list of all registered tasks.
216 *
217 * \return The task list.
218 *
219 * Each entry of the list contains an identifier which is simply a hex number.
220 * The result is dynamically allocated and must be freed by the caller.
221 */
222 char *get_task_list(struct sched *s)
223 {
224 struct task *t, *tmp;
225 char *msg = NULL;
226
227 list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) {
228 char *tmp_msg;
229 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
230 free(msg);
231 msg = tmp_msg;
232 }
233 list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) {
234 char *tmp_msg;
235 // if (t->pre_select)
236 // continue;
237 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
238 free(msg);
239 msg = tmp_msg;
240 }
241 //PARA_DEBUG_LOG("task list:\n%s", msg);
242 return msg;
243 }
244
245 /**
246 * Set the select timeout to the minimal possible value.
247 *
248 * \param s Pointer to the scheduler struct.
249 *
250 * This causes the next select() call to return immediately.
251 */
252 void sched_min_delay(struct sched *s)
253 {
254 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
255 }
256
257 /**
258 * Impose an upper bound for the timeout of the next select() call.
259 *
260 * \param to Maximal allowed timeout.
261 * \param s Pointer to the scheduler struct.
262 *
263 * If the current scheduler timeout is already smaller than \a to, this
264 * function does nothing. Otherwise the timeout for the next select() call is
265 * set to the given value.
266 *
267 * \sa sched_request_timeout_ms().
268 */
269 void sched_request_timeout(struct timeval *to, struct sched *s)
270 {
271 if (tv_diff(&s->select_timeout, to, NULL) > 0)
272 s->select_timeout = *to;
273 }
274
275 /**
276 * Force the next select() call to return before the given amount of milliseconds.
277 *
278 * \param ms The maximal allowed timeout in milliseconds.
279 * \param s Pointer to the scheduler struct.
280 *
281 * Like sched_request_timeout() this imposes an upper bound on the timeout
282 * value for the next select() call.
283 */
284 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
285 {
286 struct timeval tv;
287 ms2tv(ms, &tv);
288 sched_request_timeout(&tv, s);
289 }
290
291 /**
292 * Force the next select() call to return before the given future time.
293 *
294 * \param barrier Absolute time before select() should return.
295 * \param s Pointer to the scheduler struct.
296 *
297 * \return If \a barrier is in the past, this function does nothing and returns
298 * zero. Otherwise it returns one.
299 *
300 * \sa sched_request_barrier_or_min_delay().
301 */
302 int sched_request_barrier(struct timeval *barrier, struct sched *s)
303 {
304 struct timeval diff;
305
306 if (tv_diff(now, barrier, &diff) > 0)
307 return 0;
308 sched_request_timeout(&diff, s);
309 return 1;
310 }
311
312 /**
313 * Force the next select() call to return before the given time.
314 *
315 * \param barrier Absolute time before select() should return.
316 * \param s Pointer to the scheduler struct.
317 *
318 * \return If \a barrier is in the past, this function requests a minimal
319 * timeout and returns zero. Otherwise it returns one.
320 *
321 * \sa sched_min_delay(), sched_request_barrier().
322 */
323 int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
324 {
325 struct timeval diff;
326
327 if (tv_diff(now, barrier, &diff) > 0) {
328 sched_min_delay(s);
329 return 0;
330 }
331 sched_request_timeout(&diff, s);
332 return 1;
333 }