Simplify the scheduling code.
[paraslash.git] / sched.c
1 /*
2 * Copyright (C) 2006-2008 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 <dirent.h> /* readdir() */
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 "error.h"
20
21 static struct list_head pre_select_list, post_select_list;
22 static int initialized;
23
24 static struct timeval now_struct;
25 struct timeval *now = &now_struct;
26
27 /**
28 * Remove a task from the scheduler.
29 *
30 * \param t the task to remove
31 *
32 * If the pre_select pointer of \a t is not \p NULL, it is removed from
33 * the pre_select list of the scheduler. Same goes for \a post_select.
34 */
35 void unregister_task(struct task *t)
36 {
37 if (!initialized)
38 return;
39 PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t);
40 if (t->pre_select)
41 list_del(&t->pre_select_node);
42 if (t->post_select)
43 list_del(&t->post_select_node);
44 };
45
46
47 static void sched_preselect(struct sched *s)
48 {
49 struct task *t, *tmp;
50 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
51 t->pre_select(s, t);
52 // PARA_INFO_LOG("%s \n", t->status);
53 if (t->error >= 0)
54 continue;
55 unregister_task(t);
56 }
57 }
58
59 static void sched_post_select(struct sched *s)
60 {
61 struct task *t, *tmp;
62
63 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
64 t->post_select(s, t);
65 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
66 if (t->error >= 0)
67 continue;
68 unregister_task(t);
69 }
70 }
71
72 /**
73 * the core function for all paraslash programs
74 *
75 * \param s pointer to the scheduler struct
76 *
77 * This function updates the global \a now pointer, calls all registered
78 * pre_select hooks which may set the timeout and add any file descriptors to
79 * the fd sets of \a s. Next, it calls para_select() and makes the result available
80 * to the registered tasks by calling their post_select hook.
81 *
82 * \return Zero if no more tasks are left in either of the two lists, negative
83 * if para_select returned an error.
84 *
85 * \sa task, now.
86 */
87 int schedule(struct sched *s)
88 {
89 int ret;
90
91 if (!initialized)
92 return -E_NOT_INITIALIZED;
93 gettimeofday(now, NULL);
94 again:
95 FD_ZERO(&s->rfds);
96 FD_ZERO(&s->wfds);
97 s->timeout = s->default_timeout;
98 s->max_fileno = -1;
99 sched_preselect(s);
100 ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
101 if (ret < 0)
102 return ret;
103 gettimeofday(now, NULL);
104 sched_post_select(s);
105 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
106 return 0;
107 goto again;
108 }
109
110 /**
111 * initialize the paraslash scheduler
112 */
113 static void init_sched(void)
114 {
115 PARA_INFO_LOG("initializing scheduler\n");
116 INIT_LIST_HEAD(&pre_select_list);
117 INIT_LIST_HEAD(&post_select_list);
118 initialized = 1;
119 };
120
121 /**
122 * add a task to the scheduler
123 *
124 * \param t the task to add
125 *
126 * If the pre_select pointer of \a t is not \p NULL, it is added to
127 * the pre_select list of the scheduler. Same goes for post_select.
128 *
129 * \sa task::pre_select, task::post_select
130 */
131 void register_task(struct task *t)
132 {
133 if (!initialized)
134 init_sched();
135 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
136 if (t->pre_select) {
137 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
138 list_add_tail(&t->pre_select_node, &pre_select_list);
139 }
140 if (t->post_select) {
141 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
142 list_add_tail(&t->post_select_node, &post_select_list);
143 }
144 }
145
146 /**
147 * unregister all tasks
148 *
149 * This will cause \a schedule() to return immediately because both the
150 * \a pre_select_list and the \a post_select_list are empty.
151 */
152 void sched_shutdown(void)
153 {
154 struct task *t, *tmp;
155
156 if (!initialized)
157 return;
158 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
159 unregister_task(t);
160 /* remove tasks which do not have a pre_select hook */
161 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
162 unregister_task(t);
163 initialized = 0;
164 };
165
166 /**
167 * get the list of all registered tasks.
168 *
169 * \return the task list
170 *
171 * Each entry of the list contains an identifier which is simply a hex number
172 * that may be used in \a kill_task() to terminate the task.
173 * The result ist dynamically allocated and must be freed by the caller.
174 */
175 char *get_task_list(void)
176 {
177 struct task *t, *tmp;
178 char *msg = NULL;
179
180 if (!initialized)
181 return NULL;
182 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
183 char *tmp_msg;
184 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
185 free(msg);
186 msg = tmp_msg;
187 }
188 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
189 char *tmp_msg;
190 // if (t->pre_select)
191 // continue;
192 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
193 free(msg);
194 msg = tmp_msg;
195 }
196 //PARA_DEBUG_LOG("task list:\n%s", msg);
197 return msg;
198 }
199
200 /**
201 * simulate an error for the given task
202 *
203 * \param id the task identifier
204 *
205 * Find the task identified by \a id, set the tasks' error value to
206 * \p -E_TASK_KILLED and unregister the task.
207 *
208 * \return Positive on success, negative on errors (e.g. if \a id does not
209 * correspond to a registered task).
210 */
211 int kill_task(char *id)
212 {
213 struct task *t, *tmp;
214 char buf[20];
215
216 if (!initialized)
217 return -E_NOT_INITIALIZED;
218 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
219 sprintf(buf, "%p", t);
220 if (strcmp(id, buf))
221 continue;
222 t->error = -E_TASK_KILLED;
223 unregister_task(t);
224 return 1;
225 }
226 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
227 sprintf(buf, "%p", t);
228 if (strcmp(id, buf))
229 continue;
230 t->error = -E_TASK_KILLED;
231 unregister_task(t);
232 return 1;
233 }
234 return -E_NO_SUCH_TASK;
235 }