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
|
/* Freezer declarations */
#ifndef FREEZER_H_INCLUDED
#define FREEZER_H_INCLUDED
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/atomic.h>
#ifdef CONFIG_FREEZER
extern atomic_t system_freezing_cnt; /* nr of freezing conds in effect */
extern bool pm_freezing; /* PM freezing in effect */
extern bool pm_nosig_freezing; /* PM nosig freezing in effect */
/*
* Check if a process has been frozen
*/
static inline bool frozen(struct task_struct *p)
{
return p->flags & PF_FROZEN;
}
extern bool freezing_slow_path(struct task_struct *p);
/*
* Check if there is a request to freeze a process
*/
static inline bool freezing(struct task_struct *p)
{
if (likely(!atomic_read(&system_freezing_cnt)))
return false;
return freezing_slow_path(p);
}
/* Takes and releases task alloc lock using task_lock() */
extern void __thaw_task(struct task_struct *t);
extern bool __refrigerator(bool check_kthr_stop);
extern int freeze_processes(void);
extern int freeze_kernel_threads(void);
extern void thaw_processes(void);
extern void thaw_kernel_threads(void);
/*
* HACK: prevent sleeping while atomic warnings due to ARM signal handling
* disabling irqs
*/
static inline bool try_to_freeze_nowarn(void)
{
if (likely(!freezing(current)))
return false;
return __refrigerator(false);
}
static inline bool try_to_freeze(void)
{
might_sleep();
if (likely(!freezing(current)))
return false;
return __refrigerator(false);
}
extern bool freeze_task(struct task_struct *p);
extern bool set_freezable(void);
#ifdef CONFIG_CGROUP_FREEZER
extern bool cgroup_freezing(struct task_struct *task);
#else /* !CONFIG_CGROUP_FREEZER */
static inline bool cgroup_freezing(struct task_struct *task)
{
return false;
}
#endif /* !CONFIG_CGROUP_FREEZER */
/*
* The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
* calls wait_for_completion(&vfork) and reset right after it returns from this
* function. Next, the parent should call try_to_freeze() to freeze itself
* appropriately in case the child has exited before the freezing of tasks is
* complete. However, we don't want kernel threads to be frozen in unexpected
* places, so we allow them to block freeze_processes() instead or to set
* PF_NOFREEZE if needed. Fortunately, in the ____call_usermodehelper() case the
* parent won't really block freeze_processes(), since ____call_usermodehelper()
* (the child) does a little before exec/exit and it can't be frozen before
* waking up the parent.
*/
/**
* freezer_do_not_count - tell freezer to ignore %current
*
* Tell freezers to ignore the current task when determining whether the
* target frozen state is reached. IOW, the current task will be
* considered frozen enough by freezers.
*
* The caller shouldn't do anything which isn't allowed for a frozen task
* until freezer_cont() is called. Usually, freezer[_do_not]_count() pair
* wrap a scheduling operation and nothing much else.
*/
static inline void freezer_do_not_count(void)
{
current->flags |= PF_FREEZER_SKIP;
}
/**
* freezer_count - tell freezer to stop ignoring %current
*
* Undo freezer_do_not_count(). It tells freezers that %current should be
* considered again and tries to freeze if freezing condition is already in
* effect.
*/
static inline void freezer_count(void)
{
current->flags &= ~PF_FREEZER_SKIP;
/*
* If freezing is in progress, the following paired with smp_mb()
* in freezer_should_skip() ensures that either we see %true
* freezing() or freezer_should_skip() sees !PF_FREEZER_SKIP.
*/
smp_mb();
try_to_freeze();
}
/**
* freezer_should_skip - whether to skip a task when determining frozen
* state is reached
* @p: task in quesion
*
* This function is used by freezers after establishing %true freezing() to
* test whether a task should be skipped when determining the target frozen
* state is reached. IOW, if this function returns %true, @p is considered
* frozen enough.
*/
static inline bool freezer_should_skip(struct task_struct *p)
{
/*
* The following smp_mb() paired with the one in freezer_count()
* ensures that either freezer_count() sees %true freezing() or we
* see cleared %PF_FREEZER_SKIP and return %false. This makes it
* impossible for a task to slip frozen state testing after
* clearing %PF_FREEZER_SKIP.
*/
smp_mb();
return p->flags & PF_FREEZER_SKIP;
}
/*
* These macros are intended to be used whenever you want allow a task that's
* sleeping in TASK_UNINTERRUPTIBLE or TASK_KILLABLE state to be frozen. Note
* that neither return any clear indication of whether a freeze event happened
* while in this function.
*/
/* Like schedule(), but should not block the freezer. */
#define freezable_schedule() \
({ \
freezer_do_not_count(); \
schedule(); \
freezer_count(); \
})
/* Like schedule_timeout_killable(), but should not block the freezer. */
#define freezable_schedule_timeout_killable(timeout) \
({ \
long __retval; \
freezer_do_not_count(); \
__retval = schedule_timeout_killable(timeout); \
freezer_count(); \
__retval; \
})
/*
* Freezer-friendly wrappers around wait_event_interruptible(),
* wait_event_killable() and wait_event_interruptible_timeout(), originally
* defined in <linux/wait.h>
*/
#define wait_event_freezekillable(wq, condition) \
({ \
int __retval; \
freezer_do_not_count(); \
__retval = wait_event_killable(wq, (condition)); \
freezer_count(); \
__retval; \
})
#define wait_event_freezable(wq, condition) \
({ \
int __retval; \
for (;;) { \
__retval = wait_event_interruptible(wq, \
(condition) || freezing(current)); \
if (__retval || (condition)) \
break; \
try_to_freeze(); \
} \
__retval; \
})
#define wait_event_freezable_timeout(wq, condition, timeout) \
({ \
long __retval = timeout; \
for (;;) { \
__retval = wait_event_interruptible_timeout(wq, \
(condition) || freezing(current), \
__retval); \
if (__retval <= 0 || (condition)) \
break; \
try_to_freeze(); \
} \
__retval; \
})
#else /* !CONFIG_FREEZER */
static inline bool frozen(struct task_struct *p) { return false; }
static inline bool freezing(struct task_struct *p) { return false; }
static inline void __thaw_task(struct task_struct *t) {}
static inline bool __refrigerator(bool check_kthr_stop) { return false; }
static inline int freeze_processes(void) { return -ENOSYS; }
static inline int freeze_kernel_threads(void) { return -ENOSYS; }
static inline void thaw_processes(void) {}
static inline void thaw_kernel_threads(void) {}
static inline bool try_to_freeze(void) { return false; }
static inline void freezer_do_not_count(void) {}
static inline void freezer_count(void) {}
static inline int freezer_should_skip(struct task_struct *p) { return 0; }
static inline void set_freezable(void) {}
#define freezable_schedule() schedule()
#define freezable_schedule_timeout_killable(timeout) \
schedule_timeout_killable(timeout)
#define wait_event_freezable(wq, condition) \
wait_event_interruptible(wq, condition)
#define wait_event_freezable_timeout(wq, condition, timeout) \
wait_event_interruptible_timeout(wq, condition, timeout)
#define wait_event_freezekillable(wq, condition) \
wait_event_killable(wq, condition)
#endif /* !CONFIG_FREEZER */
#endif /* FREEZER_H_INCLUDED */
|