1 /*
2 * drivers/power/process.c - Functions for starting/stopping processes on
3 * suspend transitions.
4 *
5 * Originally from swsusp.
6 */
7
8
9 #undef DEBUG
10
11 #include <linux/interrupt.h>
12 #include <linux/suspend.h>
13 #include <linux/module.h>
14 #include <linux/syscalls.h>
15 #include <linux/freezer.h>
16
17 /*
18 * Timeout for stopping processes
19 */
20 #define TIMEOUT (20 * HZ)
21
22 #define FREEZER_KERNEL_THREADS 0
23 #define FREEZER_USER_SPACE 1
24
25 static inline int freezeable(struct task_struct * p)
26 {
27 if ((p == current) ||
28 (p->flags & PF_NOFREEZE) ||
29 (p->exit_state != 0))
30 return 0;
31 return 1;
32 }
33
34 /*
35 * freezing is complete, mark current process as frozen
36 */
37 static inline void frozen_process(void)
38 {
39 if (!unlikely(current->flags & PF_NOFREEZE)) {
40 current->flags |= PF_FROZEN;
41 wmb();
42 }
43 clear_freeze_flag(current);
44 }
45
46 /* Refrigerator is place where frozen processes are stored :-). */
47 void refrigerator(void)
48 {
49 /* Hmm, should we be allowed to suspend when there are realtime
50 processes around? */
51 long save;
52
53 task_lock(current);
54 if (freezing(current)) {
55 frozen_process();
56 task_unlock(current);
57 } else {
58 task_unlock(current);
59 return;
60 }
61 save = current->state;
62 pr_debug("%s entered refrigerator\n", current->comm);
63
64 spin_lock_irq(¤t->sighand->siglock);
65 recalc_sigpending(); /* We sent fake signal, clean it up */
66 spin_unlock_irq(¤t->sighand->siglock);
67
68 for (;;) {
69 set_current_state(TASK_UNINTERRUPTIBLE);
70 if (!frozen(current))
71 break;
72 schedule();
73 }
74 pr_debug("%s left refrigerator\n", current->comm);
75 __set_current_state(save);
76 }
77
78 static void fake_signal_wake_up(struct task_struct *p)
79 {
80 unsigned long flags;
81
82 spin_lock_irqsave(&p->sighand->siglock, flags);
83 signal_wake_up(p, 0);
84 spin_unlock_irqrestore(&p->sighand->siglock, flags);
85 }
86
87 static int has_mm(struct task_struct *p)
88 {
89 return (p->mm && !(p->flags & PF_BORROWED_MM));
90 }
91
92 /**
93 * freeze_task - send a freeze request to given task
94 * @p: task to send the request to
95 * @with_mm_only: if set, the request will only be sent if the task has its
96 * own mm
97 * Return value: 0, if @with_mm_only is set and the task has no mm of its
98 * own or the task is frozen, 1, otherwise
99 *
100 * The freeze request is sent by seting the tasks's TIF_FREEZE flag and
101 * either sending a fake signal to it or waking it up, depending on whether
102 * or not it has its own mm (ie. it is a user land task). If @with_mm_only
103 * is set and the task has no mm of its own (ie. it is a kernel thread),
104 * its TIF_FREEZE flag should not be set.
105 *
106 * The task_lock() is necessary to prevent races with exit_mm() or
107 * use_mm()/unuse_mm() from occuring.
108 */
109 static int freeze_task(struct task_struct *p, int with_mm_only)
110 {
111 int ret = 1;
112
113 task_lock(p);
114 if (freezing(p)) {
115 if (has_mm(p)) {
116 if (!signal_pending(p))
117 fake_signal_wake_up(p);
118 } else {
119 if (with_mm_only)
120 ret = 0;
121 else
122 wake_up_state(p, TASK_INTERRUPTIBLE);
123 }
124 } else {
125 rmb();
126 if (frozen(p)) {
127 ret = 0;
128 } else {
129 if (has_mm(p)) {
130 set_freeze_flag(p);
131 fake_signal_wake_up(p);
132 } else {
133 if (with_mm_only) {
134 ret = 0;
135 } else {
136 set_freeze_flag(p);
137 wake_up_state(p, TASK_INTERRUPTIBLE);
138 }
139 }
140 }
141 }
142 task_unlock(p);
143 return ret;
144 }
145
146 static void cancel_freezing(struct task_struct *p)
147 {
148 unsigned long flags;
149
150 if (freezing(p)) {
151 pr_debug(" clean up: %s\n", p->comm);
152 clear_freeze_flag(p);
153 spin_lock_irqsave(&p->sighand->siglock, flags);
154 recalc_sigpending_and_wake(p);
155 spin_unlock_irqrestore(&p->sighand->siglock, flags);
156 }
157 }
158
159 static int try_to_freeze_tasks(int freeze_user_space)
160 {
161 struct task_struct *g, *p;
162 unsigned long end_time;
163 unsigned int todo;
164 struct timeval start, end;
165 s64 elapsed_csecs64;
166 unsigned int elapsed_csecs;
167
168 do_gettimeofday(&start);
169
170 end_time = jiffies + TIMEOUT;
171 do {
172 todo = 0;
173 read_lock(&tasklist_lock);
174 do_each_thread(g, p) {
175 if (frozen(p) || !freezeable(p))
176 continue;
177
178 if (!freeze_task(p, freeze_user_space))
179 continue;
180
181 /*
182 * Now that we've done set_freeze_flag, don't
183 * perturb a task in TASK_STOPPED or TASK_TRACED.
184 * It is "frozen enough". If the task does wake
185 * up, it will immediately call try_to_freeze.
186 */
187 if (!task_is_stopped_or_traced(p) &&
188 !freezer_should_skip(p))
189 todo++;
190 } while_each_thread(g, p);
191 read_unlock(&tasklist_lock);
192 yield(); /* Yield is okay here */
193 if (time_after(jiffies, end_time))
194 break;
195 } while (todo);
196
197 do_gettimeofday(&end);
198 elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
199 do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
200 elapsed_csecs = elapsed_csecs64;
201
202 if (todo) {
203 /* This does not unfreeze processes that are already frozen
204 * (we have slightly ugly calling convention in that respect,
205 * and caller must call thaw_processes() if something fails),
206 * but it cleans up leftover PF_FREEZE requests.
207 */
208 printk("\n");
209 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
210 "(%d tasks refusing to freeze):\n",
211 elapsed_csecs / 100, elapsed_csecs % 100, todo);
212 show_state();
213 read_lock(&tasklist_lock);
214 do_each_thread(g, p) {
215 task_lock(p);
216 if (freezing(p) && !freezer_should_skip(p))
217 printk(KERN_ERR " %s\n", p->comm);
218 cancel_freezing(p);
219 task_unlock(p);
220 } while_each_thread(g, p);
221 read_unlock(&tasklist_lock);
222 } else {
223 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
224 elapsed_csecs % 100);
225 }
226
227 return todo ? -EBUSY : 0;
228 }
229
230 /**
231 * freeze_processes - tell processes to enter the refrigerator
232 */
233 int freeze_processes(void)
234 {
235 int error;
236
237 printk("Freezing user space processes ... ");
238 error = try_to_freeze_tasks(FREEZER_USER_SPACE);
239 if (error)
240 goto Exit;
241 printk("done.\n");
242
243 printk("Freezing remaining freezable tasks ... ");
244 error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
245 if (error)
246 goto Exit;
247 printk("done.");
248 Exit:
249 BUG_ON(in_atomic());
250 printk("\n");
251 return error;
252 }
253
254 static void thaw_tasks(int thaw_user_space)
255 {
256 struct task_struct *g, *p;
257
258 read_lock(&tasklist_lock);
259 do_each_thread(g, p) {
260 if (!freezeable(p))
261 continue;
262
263 if (!p->mm == thaw_user_space)
264 continue;
265
266 thaw_process(p);
267 } while_each_thread(g, p);
268 read_unlock(&tasklist_lock);
269 }
270
271 void thaw_processes(void)
272 {
273 printk("Restarting tasks ... ");
274 thaw_tasks(FREEZER_KERNEL_THREADS);
275 thaw_tasks(FREEZER_USER_SPACE);
276 schedule();
277 printk("done.\n");
278 }
279
280 EXPORT_SYMBOL(refrigerator);
281
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