summaryrefslogtreecommitdiff
path: root/kernel/power/process.c
blob: fc0df84864495f8c44261961cb6909e66d24a21e (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
/*
 * drivers/power/process.c - Functions for starting/stopping processes on 
 *                           suspend transitions.
 *
 * Originally from swsusp.
 */


#undef DEBUG

#include <linux/interrupt.h>
#include <linux/oom.h>
#include <linux/suspend.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/freezer.h>
#include <linux/delay.h>
#include <linux/workqueue.h>
#include <linux/kmod.h>

/* 
 * Timeout for stopping processes
 */
unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;

static int try_to_freeze_tasks(bool user_only)
{
	struct task_struct *g, *p;
	unsigned long end_time;
	unsigned int todo;
	bool wq_busy = false;
	struct timeval start, end;
	u64 elapsed_msecs64;
	unsigned int elapsed_msecs;
	bool wakeup = false;
	int sleep_usecs = USEC_PER_MSEC;

	do_gettimeofday(&start);

	end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);

	if (!user_only)
		freeze_workqueues_begin();

	while (true) {
		todo = 0;
		read_lock(&tasklist_lock);
		do_each_thread(g, p) {
			if (p == current || !freeze_task(p))
				continue;

			if (!freezer_should_skip(p))
				todo++;
		} while_each_thread(g, p);
		read_unlock(&tasklist_lock);

		if (!user_only) {
			wq_busy = freeze_workqueues_busy();
			todo += wq_busy;
		}

		if (!todo || time_after(jiffies, end_time))
			break;

		if (pm_wakeup_pending()) {
			wakeup = true;
			break;
		}

		/*
		 * We need to retry, but first give the freezing tasks some
		 * time to enter the refrigerator.  Start with an initial
		 * 1 ms sleep followed by exponential backoff until 8 ms.
		 */
		usleep_range(sleep_usecs / 2, sleep_usecs);
		if (sleep_usecs < 8 * USEC_PER_MSEC)
			sleep_usecs *= 2;
	}

	do_gettimeofday(&end);
	elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
	do_div(elapsed_msecs64, NSEC_PER_MSEC);
	elapsed_msecs = elapsed_msecs64;

	if (todo) {
		printk("\n");
		printk(KERN_ERR "Freezing of tasks %s after %d.%03d seconds "
		       "(%d tasks refusing to freeze, wq_busy=%d):\n",
		       wakeup ? "aborted" : "failed",
		       elapsed_msecs / 1000, elapsed_msecs % 1000,
		       todo - wq_busy, wq_busy);

		if (!wakeup) {
			read_lock(&tasklist_lock);
			do_each_thread(g, p) {
				if (p != current && !freezer_should_skip(p)
				    && freezing(p) && !frozen(p))
					sched_show_task(p);
			} while_each_thread(g, p);
			read_unlock(&tasklist_lock);
		}
	} else {
		printk("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
			elapsed_msecs % 1000);
	}

	return todo ? -EBUSY : 0;
}

/**
 * freeze_processes - Signal user space processes to enter the refrigerator.
 *
 * On success, returns 0.  On failure, -errno and system is fully thawed.
 */
int freeze_processes(void)
{
	int error;

	error = __usermodehelper_disable(UMH_FREEZING);
	if (error)
		return error;

	if (!pm_freezing)
		atomic_inc(&system_freezing_cnt);

	printk("Freezing user space processes ... ");
	pm_freezing = true;
	error = try_to_freeze_tasks(true);
	if (!error) {
		printk("done.");
		__usermodehelper_set_disable_depth(UMH_DISABLED);
		oom_killer_disable();
	}
	printk("\n");
	BUG_ON(in_atomic());

	if (error)
		thaw_processes();
	return error;
}

/**
 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 *
 * On success, returns 0.  On failure, -errno and only the kernel threads are
 * thawed, so as to give a chance to the caller to do additional cleanups
 * (if any) before thawing the userspace tasks. So, it is the responsibility
 * of the caller to thaw the userspace tasks, when the time is right.
 */
int freeze_kernel_threads(void)
{
	int error;

	printk("Freezing remaining freezable tasks ... ");
	pm_nosig_freezing = true;
	error = try_to_freeze_tasks(false);
	if (!error)
		printk("done.");

	printk("\n");
	BUG_ON(in_atomic());

	if (error)
		thaw_kernel_threads();
	return error;
}

void thaw_processes(void)
{
	struct task_struct *g, *p;

	if (pm_freezing)
		atomic_dec(&system_freezing_cnt);
	pm_freezing = false;
	pm_nosig_freezing = false;

	oom_killer_enable();

	printk("Restarting tasks ... ");

	thaw_workqueues();

	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		__thaw_task(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);

	usermodehelper_enable();

	schedule();
	printk("done.\n");
}

void thaw_kernel_threads(void)
{
	struct task_struct *g, *p;

	pm_nosig_freezing = false;
	printk("Restarting kernel threads ... ");

	thaw_workqueues();

	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
			__thaw_task(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);

	schedule();
	printk("done.\n");
}