1 // SPDX-License-Identifier: GPL-2.0-only 1
2 /*
3 * kernel/freezer.c - Function to freeze a pro
4 *
5 * Originally from kernel/power/process.c
6 */
7
8 #include <linux/interrupt.h>
9 #include <linux/suspend.h>
10 #include <linux/export.h>
11 #include <linux/syscalls.h>
12 #include <linux/freezer.h>
13 #include <linux/kthread.h>
14
15 /* total number of freezing conditions in effe
16 DEFINE_STATIC_KEY_FALSE(freezer_active);
17 EXPORT_SYMBOL(freezer_active);
18
19 /*
20 * indicate whether PM freezing is in effect,
21 * system_transition_mutex
22 */
23 bool pm_freezing;
24 bool pm_nosig_freezing;
25
26 /* protects freezing and frozen transitions */
27 static DEFINE_SPINLOCK(freezer_lock);
28
29 /**
30 * freezing_slow_path - slow path for testing
31 * @p: task to be tested
32 *
33 * This function is called by freezing() if fr
34 * and tests whether @p needs to enter and sta
35 * called under any context. The freezers are
36 * target tasks see the updated state.
37 */
38 bool freezing_slow_path(struct task_struct *p)
39 {
40 if (p->flags & (PF_NOFREEZE | PF_SUSPE
41 return false;
42
43 if (test_tsk_thread_flag(p, TIF_MEMDIE
44 return false;
45
46 if (pm_nosig_freezing || cgroup_freezi
47 return true;
48
49 if (pm_freezing && !(p->flags & PF_KTH
50 return true;
51
52 return false;
53 }
54 EXPORT_SYMBOL(freezing_slow_path);
55
56 bool frozen(struct task_struct *p)
57 {
58 return READ_ONCE(p->__state) & TASK_FR
59 }
60
61 /* Refrigerator is place where frozen processe
62 bool __refrigerator(bool check_kthr_stop)
63 {
64 unsigned int state = get_current_state
65 bool was_frozen = false;
66
67 pr_debug("%s entered refrigerator\n",
68
69 WARN_ON_ONCE(state && !(state & TASK_N
70
71 for (;;) {
72 bool freeze;
73
74 raw_spin_lock_irq(¤t->pi
75 WRITE_ONCE(current->__state, T
76 /* unstale saved_state so that
77 current->saved_state = TASK_RU
78 raw_spin_unlock_irq(¤t->
79
80 spin_lock_irq(&freezer_lock);
81 freeze = freezing(current) &&
82 spin_unlock_irq(&freezer_lock)
83
84 if (!freeze)
85 break;
86
87 was_frozen = true;
88 schedule();
89 }
90 __set_current_state(TASK_RUNNING);
91
92 pr_debug("%s left refrigerator\n", cur
93
94 return was_frozen;
95 }
96 EXPORT_SYMBOL(__refrigerator);
97
98 static void fake_signal_wake_up(struct task_st
99 {
100 unsigned long flags;
101
102 if (lock_task_sighand(p, &flags)) {
103 signal_wake_up(p, 0);
104 unlock_task_sighand(p, &flags)
105 }
106 }
107
108 static int __set_task_frozen(struct task_struc
109 {
110 unsigned int state = READ_ONCE(p->__st
111
112 /*
113 * Allow freezing the sched_delayed ta
114 * ttwu() fixes them up, so it is safe
115 * of waiting for them to get fully de
116 */
117 if (task_is_runnable(p))
118 return 0;
119
120 if (p != current && task_curr(p))
121 return 0;
122
123 if (!(state & (TASK_FREEZABLE | __TASK
124 return 0;
125
126 /*
127 * Only TASK_NORMAL can be augmented w
128 * can suffer spurious wakeups.
129 */
130 if (state & TASK_FREEZABLE)
131 WARN_ON_ONCE(!(state & TASK_NO
132
133 #ifdef CONFIG_LOCKDEP
134 /*
135 * It's dangerous to freeze with locks
136 */
137 if (!(state & __TASK_FREEZABLE_UNSAFE)
138 WARN_ON_ONCE(debug_locks && p-
139 #endif
140
141 p->saved_state = p->__state;
142 WRITE_ONCE(p->__state, TASK_FROZEN);
143 return TASK_FROZEN;
144 }
145
146 static bool __freeze_task(struct task_struct *
147 {
148 /* TASK_FREEZABLE|TASK_STOPPED|TASK_TR
149 return task_call_func(p, __set_task_fr
150 }
151
152 /**
153 * freeze_task - send a freeze request to give
154 * @p: task to send the request to
155 *
156 * If @p is freezing, the freeze request is se
157 * signal (if it's not a kernel thread) or wak
158 * thread).
159 *
160 * RETURNS:
161 * %false, if @p is not freezing or already fr
162 */
163 bool freeze_task(struct task_struct *p)
164 {
165 unsigned long flags;
166
167 spin_lock_irqsave(&freezer_lock, flags
168 if (!freezing(p) || frozen(p) || __fre
169 spin_unlock_irqrestore(&freeze
170 return false;
171 }
172
173 if (!(p->flags & PF_KTHREAD))
174 fake_signal_wake_up(p);
175 else
176 wake_up_state(p, TASK_NORMAL);
177
178 spin_unlock_irqrestore(&freezer_lock,
179 return true;
180 }
181
182 /*
183 * Restore the saved_state before the task ent
184 * in the __refrigerator(), saved_state == TAS
185 * here. For tasks which were TASK_NORMAL | TA
186 * is restored unless they got an expected wak
187 * Returns 1 if the task state was restored.
188 */
189 static int __restore_freezer_state(struct task
190 {
191 unsigned int state = p->saved_state;
192
193 if (state != TASK_RUNNING) {
194 WRITE_ONCE(p->__state, state);
195 p->saved_state = TASK_RUNNING;
196 return 1;
197 }
198
199 return 0;
200 }
201
202 void __thaw_task(struct task_struct *p)
203 {
204 unsigned long flags;
205
206 spin_lock_irqsave(&freezer_lock, flags
207 if (WARN_ON_ONCE(freezing(p)))
208 goto unlock;
209
210 if (!frozen(p) || task_call_func(p, __
211 goto unlock;
212
213 wake_up_state(p, TASK_FROZEN);
214 unlock:
215 spin_unlock_irqrestore(&freezer_lock,
216 }
217
218 /**
219 * set_freezable - make %current freezable
220 *
221 * Mark %current freezable and enter refrigera
222 */
223 bool set_freezable(void)
224 {
225 might_sleep();
226
227 /*
228 * Modify flags while holding freezer_
229 * freezer notices that we aren't froz
230 * condition is visible to try_to_free
231 */
232 spin_lock_irq(&freezer_lock);
233 current->flags &= ~PF_NOFREEZE;
234 spin_unlock_irq(&freezer_lock);
235
236 return try_to_freeze();
237 }
238 EXPORT_SYMBOL(set_freezable);
239
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