command_util: Generate properly documented command header files.
[paraslash.git] / sched.c
1 /*
2 * Copyright (C) 2006-2009 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 static void unregister_task(struct task *t)
36 {
37 if (!initialized)
38 return;
39 PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
40 t->error <0? para_strerror(-t->error) : "shutdown");
41 if (t->pre_select)
42 list_del(&t->pre_select_node);
43 if (t->post_select)
44 list_del(&t->post_select_node);
45 t->error = -E_TASK_UNREGISTERED;
46 }
47
48
49 static void sched_preselect(struct sched *s)
50 {
51 struct task *t, *tmp;
52 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
53 if (t->error >= 0 && t->pre_select)
54 t->pre_select(s, t);
55 // PARA_INFO_LOG("%s \n", t->status);
56 if (t->error >= 0)
57 continue;
58 /*
59 * We have to check whether the list is empty because the call
60 * to ->pre_select() might have called sched_shutdown(). In
61 * this case t has been unregistered already, so we must not
62 * unregister it again.
63 */
64 if (list_empty(&pre_select_list))
65 return;
66 unregister_task(t);
67 }
68 }
69
70 static void sched_post_select(struct sched *s)
71 {
72 struct task *t, *tmp;
73
74 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
75 if (t->error >= 0)
76 t->post_select(s, t);
77 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
78 if (t->error >= 0)
79 continue;
80 /* nec., see sched_preselect() */
81 if (list_empty(&post_select_list))
82 return;
83 unregister_task(t);
84 }
85 }
86
87 /**
88 * The core function for all paraslash programs.
89 *
90 * \param s Pointer to the scheduler struct.
91 *
92 * This function updates the global \a now pointer, calls all registered
93 * pre_select hooks which may set the timeout and add any file descriptors to
94 * the fd sets of \a s. Next, it calls para_select() and makes the result available
95 * to the registered tasks by calling their post_select hook.
96 *
97 * \return Zero if no more tasks are left in either of the two lists, negative
98 * if para_select returned an error.
99 *
100 * \sa task, now.
101 */
102 int schedule(struct sched *s)
103 {
104 int ret;
105
106 if (!initialized)
107 return -E_NOT_INITIALIZED;
108 if (!s->select_function)
109 s->select_function = para_select;
110 gettimeofday(now, NULL);
111 again:
112 FD_ZERO(&s->rfds);
113 FD_ZERO(&s->wfds);
114 s->timeout = s->default_timeout;
115 s->max_fileno = -1;
116 sched_preselect(s);
117 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
118 return 0;
119 ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
120 if (ret < 0)
121 return ret;
122 gettimeofday(now, NULL);
123 sched_post_select(s);
124 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
125 return 0;
126 goto again;
127 }
128
129 /**
130 * Initialize the paraslash scheduler.
131 */
132 static void init_sched(void)
133 {
134 PARA_INFO_LOG("initializing scheduler\n");
135 INIT_LIST_HEAD(&pre_select_list);
136 INIT_LIST_HEAD(&post_select_list);
137 initialized = 1;
138 }
139
140 /**
141 * Add a task to the scheduler.
142 *
143 * \param t the task to add
144 *
145 * If the pre_select pointer of \a t is not \p NULL, it is added to
146 * the pre_select list of the scheduler. Same goes for post_select.
147 *
148 * \sa task::pre_select, task::post_select
149 */
150 void register_task(struct task *t)
151 {
152 if (!initialized)
153 init_sched();
154 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
155 if (t->pre_select) {
156 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
157 list_add_tail(&t->pre_select_node, &pre_select_list);
158 }
159 if (t->post_select) {
160 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
161 list_add_tail(&t->post_select_node, &post_select_list);
162 }
163 }
164
165 /**
166 * Unregister all tasks.
167 *
168 * This will cause \a schedule() to return immediately because both the
169 * \a pre_select_list and the \a post_select_list are empty.
170 */
171 void sched_shutdown(void)
172 {
173 struct task *t, *tmp;
174
175 if (!initialized)
176 return;
177 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
178 unregister_task(t);
179 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
180 unregister_task(t);
181 initialized = 0;
182 }
183
184 /**
185 * Get the list of all registered tasks.
186 *
187 * \return The task list.
188 *
189 * Each entry of the list contains an identifier which is simply a hex number
190 * that may be used in \a kill_task() to terminate the task.
191 * The result ist dynamically allocated and must be freed by the caller.
192 */
193 char *get_task_list(void)
194 {
195 struct task *t, *tmp;
196 char *msg = NULL;
197
198 if (!initialized)
199 return NULL;
200 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
201 char *tmp_msg;
202 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
203 free(msg);
204 msg = tmp_msg;
205 }
206 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
207 char *tmp_msg;
208 // if (t->pre_select)
209 // continue;
210 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
211 free(msg);
212 msg = tmp_msg;
213 }
214 //PARA_DEBUG_LOG("task list:\n%s", msg);
215 return msg;
216 }
217
218 /**
219 * Simulate an error for the given task.
220 *
221 * \param id The task identifier.
222 *
223 * Find the task identified by \a id, set the tasks' error value to
224 * \p -E_TASK_KILLED and unregister the task.
225 *
226 * \return Positive on success, negative on errors (e.g. if \a id does not
227 * correspond to a registered task).
228 */
229 int kill_task(char *id)
230 {
231 struct task *t, *tmp;
232 char buf[20];
233
234 if (!initialized)
235 return -E_NOT_INITIALIZED;
236 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
237 sprintf(buf, "%p", t);
238 if (strcmp(id, buf))
239 continue;
240 t->error = -E_TASK_KILLED;
241 return 1;
242 }
243 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
244 sprintf(buf, "%p", t);
245 if (strcmp(id, buf))
246 continue;
247 t->error = -E_TASK_KILLED;
248 return 1;
249 }
250 return -E_NO_SUCH_TASK;
251 }