Merge branch 't/smaller_tarball'
[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 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 inline bool timeout_is_zero(struct sched *s)
51 {
52 struct timeval *tv = &s->select_timeout;
53 return tv->tv_sec == 0 && tv->tv_usec == 0;
54 }
55
56 static void sched_preselect(struct sched *s)
57 {
58 struct task *t, *tmp;
59 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
60 if (t->error < 0) {
61 unregister_task(t);
62 continue;
63 }
64 if (!t->pre_select)
65 continue;
66 t->pre_select(s, t);
67 if (timeout_is_zero(s))
68 break;
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 /*
103 * We have to check whether the list is empty because the call
104 * to ->post_select() might have called sched_shutdown(). In
105 * this case t has been unregistered already, so we must not
106 * unregister it again.
107 */
108 if (list_empty(&post_select_list))
109 return;
110 unregister_task(t);
111 }
112 }
113
114 /**
115 * The core function for all paraslash programs.
116 *
117 * \param s Pointer to the scheduler struct.
118 *
119 * This function updates the global \a now pointer, calls all registered
120 * pre_select hooks which may set the timeout and add any file descriptors to
121 * the fd sets of \a s. Next, it calls para_select() and makes the result available
122 * to the registered tasks by calling their post_select hook.
123 *
124 * \return Zero if no more tasks are left in either of the two lists, negative
125 * if para_select returned an error.
126 *
127 * \sa task, now.
128 */
129 int schedule(struct sched *s)
130 {
131 int ret;
132
133 if (!initialized)
134 return -E_NOT_INITIALIZED;
135 if (!s->select_function)
136 s->select_function = para_select;
137 again:
138 FD_ZERO(&s->rfds);
139 FD_ZERO(&s->wfds);
140 s->select_timeout = s->default_timeout;
141 s->max_fileno = -1;
142 gettimeofday(now, NULL);
143 sched_preselect(s);
144 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
145 return 0;
146 if (!timeout_is_zero(s)) {
147 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
148 &s->select_timeout);
149 if (ret < 0)
150 return ret;
151 if (ret == 0) {
152 /*
153 * APUE: Be careful not to check the descriptor sets on return
154 * unless the return value is greater than zero. The return
155 * state of the descriptor sets is implementation dependent if
156 * either a signal is caught or the timer expires.
157 */
158 FD_ZERO(&s->rfds);
159 FD_ZERO(&s->wfds);
160 }
161 gettimeofday(now, NULL);
162 }
163 sched_post_select(s);
164 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
165 return 0;
166 goto again;
167 }
168
169 /*
170 * Initialize the paraslash scheduler.
171 */
172 static void init_sched(void)
173 {
174 PARA_INFO_LOG("initializing scheduler\n");
175 INIT_LIST_HEAD(&pre_select_list);
176 INIT_LIST_HEAD(&post_select_list);
177 initialized = 1;
178 }
179
180 /**
181 * Add a task to the scheduler.
182 *
183 * \param t the task to add
184 *
185 * If the pre_select pointer of \a t is not \p NULL, it is added to
186 * the pre_select list of the scheduler. Same goes for post_select.
187 *
188 * \sa task::pre_select, task::post_select
189 */
190 void register_task(struct task *t)
191 {
192 if (!initialized)
193 init_sched();
194 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
195 if (t->pre_select) {
196 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
197 list_add_tail(&t->pre_select_node, &pre_select_list);
198 }
199 if (t->post_select) {
200 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
201 list_add_tail(&t->post_select_node, &post_select_list);
202 }
203 }
204
205 /**
206 * Unregister all tasks.
207 *
208 * This will cause \a schedule() to return immediately because both the
209 * \a pre_select_list and the \a post_select_list are empty. This function
210 * must be called from the post_select (rather than the pre_select) method.
211 */
212 void sched_shutdown(void)
213 {
214 struct task *t, *tmp;
215
216 if (!initialized)
217 return;
218 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
219 t->error = -E_SCHED_SHUTDOWN;
220 unregister_task(t);
221 }
222 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
223 t->error = -E_SCHED_SHUTDOWN;
224 unregister_task(t);
225 }
226 initialized = 0;
227 }
228
229 /**
230 * Get the list of all registered tasks.
231 *
232 * \return The task list.
233 *
234 * Each entry of the list contains an identifier which is simply a hex number.
235 * The result is dynamically allocated and must be freed by the caller.
236 */
237 char *get_task_list(void)
238 {
239 struct task *t, *tmp;
240 char *msg = NULL;
241
242 if (!initialized)
243 return NULL;
244 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
245 char *tmp_msg;
246 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
247 free(msg);
248 msg = tmp_msg;
249 }
250 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
251 char *tmp_msg;
252 // if (t->pre_select)
253 // continue;
254 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
255 free(msg);
256 msg = tmp_msg;
257 }
258 //PARA_DEBUG_LOG("task list:\n%s", msg);
259 return msg;
260 }
261
262 /**
263 * Set the select timeout to the minimal possible value.
264 *
265 * \param s Pointer to the scheduler struct.
266 *
267 * This causes the next select() call to return immediately.
268 */
269 void sched_min_delay(struct sched *s)
270 {
271 s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0;
272 }
273
274 /**
275 * Impose