summaryrefslogtreecommitdiffstats
path: root/kernel/power/process.c
blob: 4da125ee533de0fecd5652b6518b2b8730d7dbf9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
/*
 * drivers/power/process.c - Functions for starting/stopping processes on 
 *                           suspend transitions.
 *
 * Originally from swsusp.
 */


#undef DEBUG

#include <linux/interrupt.h>
#include <linux/suspend.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/freezer.h>

/* 
 * Timeout for stopping processes
 */
#define TIMEOUT	(20 * HZ)

#define FREEZER_KERNEL_THREADS 0
#define FREEZER_USER_SPACE 1

static inline int freezeable(struct task_struct * p)
{
	if ((p == current) ||
	    (p->flags & PF_NOFREEZE) ||
	    (p->exit_state != 0))
		return 0;
	return 1;
}

/*
 * freezing is complete, mark current process as frozen
 */
static inline void frozen_process(void)
{
	if (!unlikely(current->flags & PF_NOFREEZE)) {
		current->flags |= PF_FROZEN;
		wmb();
	}
	clear_freeze_flag(current);
}

/* Refrigerator is place where frozen processes are stored :-). */
void refrigerator(void)
{
	/* Hmm, should we be allowed to suspend when there are realtime
	   processes around? */
	long save;

	task_lock(current);
	if (freezing(current)) {
		frozen_process();
		task_unlock(current);
	} else {
		task_unlock(current);
		return;
	}
	save = current->state;
	pr_debug("%s entered refrigerator\n", current->comm);

	spin_lock_irq(&current->sighand->siglock);
	recalc_sigpending(); /* We sent fake signal, clean it up */
	spin_unlock_irq(&current->sighand->siglock);

	for (;;) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (!frozen(current))
			break;
		schedule();
	}
	pr_debug("%s left refrigerator\n", current->comm);
	__set_current_state(save);
}

static void fake_signal_wake_up(struct task_struct *p, int resume)
{
	unsigned long flags;

	spin_lock_irqsave(&p->sighand->siglock, flags);
	signal_wake_up(p, resume);
	spin_unlock_irqrestore(&p->sighand->siglock, flags);
}

static void send_fake_signal(struct task_struct *p)
{
	if (p->state == TASK_STOPPED)
		force_sig_specific(SIGSTOP, p);
	fake_signal_wake_up(p, p->state == TASK_STOPPED);
}

static int has_mm(struct task_struct *p)
{
	return (p->mm && !(p->flags & PF_BORROWED_MM));
}

/**
 *	freeze_task - send a freeze request to given task
 *	@p: task to send the request to
 *	@with_mm_only: if set, the request will only be sent if the task has its
 *		own mm
 *	Return value: 0, if @with_mm_only is set and the task has no mm of its
 *		own or the task is frozen, 1, otherwise
 *
 *	The freeze request is sent by seting the tasks's TIF_FREEZE flag and
 *	either sending a fake signal to it or waking it up, depending on whether
 *	or not it has its own mm (ie. it is a user land task).  If @with_mm_only
 *	is set and the task has no mm of its own (ie. it is a kernel thread),
 *	its TIF_FREEZE flag should not be set.
 *
 *	The task_lock() is necessary to prevent races with exit_mm() or
 *	use_mm()/unuse_mm() from occuring.
 */
static int freeze_task(struct task_struct *p, int with_mm_only)
{
	int ret = 1;

	task_lock(p);
	if (freezing(p)) {
		if (has_mm(p)) {
			if (!signal_pending(p))
				fake_signal_wake_up(p, 0);
		} else {
			if (with_mm_only)
				ret = 0;
			else
				wake_up_state(p, TASK_INTERRUPTIBLE);
		}
	} else {
		rmb();
		if (frozen(p)) {
			ret = 0;
		} else {
			if (has_mm(p)) {
				set_freeze_flag(p);
				send_fake_signal(p);
			} else {
				if (with_mm_only) {
					ret = 0;
				} else {
					set_freeze_flag(p);
					wake_up_state(p, TASK_INTERRUPTIBLE);
				}
			}
		}
	}
	task_unlock(p);
	return ret;
}

static void cancel_freezing(struct task_struct *p)
{
	unsigned long flags;

	if (freezing(p)) {
		pr_debug("  clean up: %s\n", p->comm);
		clear_freeze_flag(p);
		spin_lock_irqsave(&p->sighand->siglock, flags);
		recalc_sigpending_and_wake(p);
		spin_unlock_irqrestore(&p->sighand->siglock, flags);
	}
}

static int try_to_freeze_tasks(int freeze_user_space)
{
	struct task_struct *g, *p;
	unsigned long end_time;
	unsigned int todo;

	end_time = jiffies + TIMEOUT;
	do {
		todo = 0;
		read_lock(&tasklist_lock);
		do_each_thread(g, p) {
			if (frozen(p) || !freezeable(p))
				continue;

			if (p->state == TASK_TRACED && frozen(p->parent)) {
				cancel_freezing(p);
				continue;
			}

			if (!freeze_task(p, freeze_user_space))
				continue;

			if (!freezer_should_skip(p))
				todo++;
		} while_each_thread(g, p);
		read_unlock(&tasklist_lock);
		yield();			/* Yield is okay here */
		if (time_after(jiffies, end_time))
			break;
	} while (todo);

	if (todo) {
		/* This does not unfreeze processes that are already frozen
		 * (we have slightly ugly calling convention in that respect,
		 * and caller must call thaw_processes() if something fails),
		 * but it cleans up leftover PF_FREEZE requests.
		 */
		printk("\n");
		printk(KERN_ERR "Freezing of %s timed out after %d seconds "
				"(%d tasks refusing to freeze):\n",
				freeze_user_space ? "user space " : "tasks ",
				TIMEOUT / HZ, todo);
		show_state();
		read_lock(&tasklist_lock);
		do_each_thread(g, p) {
			task_lock(p);
			if (freezing(p) && !freezer_should_skip(p))
				printk(KERN_ERR " %s\n", p->comm);
			cancel_freezing(p);
			task_unlock(p);
		} while_each_thread(g, p);
		read_unlock(&tasklist_lock);
	}

	return todo ? -EBUSY : 0;
}

/**
 *	freeze_processes - tell processes to enter the refrigerator
 */
int freeze_processes(void)
{
	int error;

	printk("Stopping tasks ... ");
	error = try_to_freeze_tasks(FREEZER_USER_SPACE);
	if (error)
		return error;

	error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
	if (error)
		return error;

	printk("done.\n");
	BUG_ON(in_atomic());
	return 0;
}

static void thaw_tasks(int thaw_user_space)
{
	struct task_struct *g, *p;

	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		if (!freezeable(p))
			continue;

		if (!p->mm == thaw_user_space)
			continue;

		thaw_process(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);
}

void thaw_processes(void)
{
	printk("Restarting tasks ... ");
	thaw_tasks(FREEZER_KERNEL_THREADS);
	thaw_tasks(FREEZER_USER_SPACE);
	schedule();
	printk("done.\n");
}

EXPORT_SYMBOL(refrigerator);