unregister_task(): Set error status to E_TASK_UNREGISTERED
[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 t->error = -E_TASK_UNREGISTERED;
45 };
46
47
48 static void sched_preselect(struct sched *s)
49 {
50 struct task *t, *tmp;
51 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
52 if (t->error >= 0)
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 if (t->error >= 0)
75 t->post_select(s, t);
76 // PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
77 if (t->error >= 0)
78 continue;
79 /* nec., see sched_preselect() */
80 if (list_empty(&post_select_list))
81 return;
82 unregister_task(t);
83 }
84 }
85
86 /**
87 * The core function for all paraslash programs.
88 *
89 * \param s Pointer to the scheduler struct.
90 *
91 * This function updates the global \a now pointer, calls all registered
92 * pre_select hooks which may set the timeout and add any file descriptors to
93 * the fd sets of \a s. Next, it calls para_select() and makes the result available
94 * to the registered tasks by calling their post_select hook.
95 *
96 * \return Zero if no more tasks are left in either of the two lists, negative
97 * if para_select returned an error.
98 *
99 * \sa task, now.
100 */
101 int schedule(struct sched *s)
102 {
103 int ret;
104
105 if (!initialized)
106 return -E_NOT_INITIALIZED;
107 gettimeofday(now, NULL);
108 again:
109 FD_ZERO(&s->rfds);
110 FD_ZERO(&s->wfds);
111 s->timeout = s->default_timeout;
112 s->max_fileno = -1;
113 sched_preselect(s);
114 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
115 return 0;
116 ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
117 if (ret < 0)
118 return ret;
119 gettimeofday(now, NULL);
120 sched_post_select(s);
121 if (list_empty(&pre_select_list) && list_empty(&post_select_list))
122 return 0;
123 goto again;
124 }
125
126 /**
127 * Initialize the paraslash scheduler.
128 */
129 static void init_sched(void)
130 {
131 PARA_INFO_LOG("initializing scheduler\n");
132 INIT_LIST_HEAD(&pre_select_list);
133 INIT_LIST_HEAD(&post_select_list);
134 initialized = 1;
135 };
136
137 /**
138 * Add a task to the scheduler.
139 *
140 * \param t the task to add
141 *
142 * If the pre_select pointer of \a t is not \p NULL, it is added to
143 * the pre_select list of the scheduler. Same goes for post_select.
144 *
145 * \sa task::pre_select, task::post_select
146 */
147 void register_task(struct task *t)
148 {
149 if (!initialized)
150 init_sched();
151 PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
152 if (t->pre_select) {
153 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
154 list_add_tail(&t->pre_select_node, &pre_select_list);
155 }
156 if (t->post_select) {
157 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
158 list_add_tail(&t->post_select_node, &post_select_list);
159 }
160 }
161
162 /**
163 * Unregister all tasks.
164 *
165 * This will cause \a schedule() to return immediately because both the
166 * \a pre_select_list and the \a post_select_list are empty.
167 */
168 void sched_shutdown(void)
169 {
170 struct task *t, *tmp;
171
172 if (!initialized)
173 return;
174 list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
175 unregister_task(t);
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 return 1;
239 }
240 list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
241 sprintf(buf, "%p", t);
242 if (strcmp(id, buf))
243 continue;
244 t->error = -E_TASK_KILLED;
245 return 1;
246 }
247 return -E_NO_SUCH_TASK;
248 }