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
|
/*
* 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(¤t->sighand->siglock);
recalc_sigpending(); /* We sent fake signal, clean it up */
spin_unlock_irq(¤t->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 freeze_task(struct task_struct *p)
{
unsigned long flags;
if (!freezing(p)) {
rmb();
if (!frozen(p)) {
set_freeze_flag(p);
if (p->state == TASK_STOPPED)
force_sig_specific(SIGSTOP, p);
spin_lock_irqsave(&p->sighand->siglock, flags);
signal_wake_up(p, p->state == TASK_STOPPED);
spin_unlock_irqrestore(&p->sighand->siglock, flags);
}
}
}
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 (freeze_user_space) {
if (p->state == TASK_TRACED &&
frozen(p->parent)) {
cancel_freezing(p);
continue;
}
/*
* Kernel threads should not have TIF_FREEZE set
* at this point, so we must ensure that either
* p->mm is not NULL *and* PF_BORROWED_MM is
* unset, or TIF_FRREZE is left unset.
* The task_lock() is necessary to prevent races
* with exit_mm() or use_mm()/unuse_mm() from
* occuring.
*/
task_lock(p);
if (!p->mm || (p->flags & PF_BORROWED_MM)) {
task_unlock(p);
continue;
}
freeze_task(p);
task_unlock(p);
} else {
freeze_task(p);
}
if (!freezer_should_skip(p))
todo++;
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
yield(); /* Yield is okay here */
if (todo && 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;
sys_sync();
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);
|
