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