1 // SPDX-License-Identifier: GPL-2.0-only
3  * kernel/freezer.c - Function to freeze a process
30  * freezing_slow_path - slow path for testing whether a task needs to be frozen
31  * @p: task to be tested
34  * and tests whether @p needs to enter and stay in frozen state.  Can be
36  * target tasks see the updated state.
38 bool freezing_slow_path(struct task_struct *p)  in freezing_slow_path()  argument
40 	if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK))  in freezing_slow_path()
43 	if (test_tsk_thread_flag(p, TIF_MEMDIE))  in freezing_slow_path()
46 	if (pm_nosig_freezing || cgroup_freezing(p))  in freezing_slow_path()
49 	if (pm_freezing && !(p->flags & PF_KTHREAD))  in freezing_slow_path()
56 bool frozen(struct task_struct *p)  in frozen()  argument
58 	return READ_ONCE(p->__state) & TASK_FROZEN;  in frozen()
61 /* Refrigerator is place where frozen processes are stored :-). */
64 	unsigned int state = get_current_state();  in __refrigerator()  local
67 	pr_debug("%s entered refrigerator\n", current->comm);  in __refrigerator()
69 	WARN_ON_ONCE(state && !(state & TASK_NORMAL));  in __refrigerator()
74 		raw_spin_lock_irq(&current->pi_lock);  in __refrigerator()
75 		WRITE_ONCE(current->__state, TASK_FROZEN);  in __refrigerator()
77 		current->saved_state = TASK_RUNNING;  in __refrigerator()
78 		raw_spin_unlock_irq(&current->pi_lock);  in __refrigerator()
92 	pr_debug("%s left refrigerator\n", current->comm);  in __refrigerator()
98 static void fake_signal_wake_up(struct task_struct *p)  in fake_signal_wake_up()  argument
102 	if (lock_task_sighand(p, &flags)) {  in fake_signal_wake_up()
103 		signal_wake_up(p, 0);  in fake_signal_wake_up()
104 		unlock_task_sighand(p, &flags);  in fake_signal_wake_up()
108 static int __set_task_frozen(struct task_struct *p, void *arg)  in __set_task_frozen()  argument
110 	unsigned int state = READ_ONCE(p->__state);  in __set_task_frozen()  local
114 	 * ttwu() fixes them up, so it is safe to swap their state now, instead  in __set_task_frozen()
117 	if (task_is_runnable(p))  in __set_task_frozen()
120 	if (p != current && task_curr(p))  in __set_task_frozen()
123 	if (!(state & (TASK_FREEZABLE | __TASK_STOPPED | __TASK_TRACED)))  in __set_task_frozen()
130 	if (state & TASK_FREEZABLE)  in __set_task_frozen()
131 		WARN_ON_ONCE(!(state & TASK_NORMAL));  in __set_task_frozen()
137 	if (!(state & __TASK_FREEZABLE_UNSAFE))  in __set_task_frozen()
138 		WARN_ON_ONCE(debug_locks && p->lockdep_depth);  in __set_task_frozen()
141 	p->saved_state = p->__state;  in __set_task_frozen()
142 	WRITE_ONCE(p->__state, TASK_FROZEN);  in __set_task_frozen()
146 static bool __freeze_task(struct task_struct *p)  in __freeze_task()  argument
148 	/* TASK_FREEZABLE|TASK_STOPPED|TASK_TRACED -> TASK_FROZEN */  in __freeze_task()
149 	return task_call_func(p, __set_task_frozen, NULL);  in __freeze_task()
153  * freeze_task - send a freeze request to given task
154  * @p: task to send the request to
156  * If @p is freezing, the freeze request is sent either by sending a fake
161  * %false, if @p is not freezing or already frozen; %true, otherwise
163 bool freeze_task(struct task_struct *p)  in freeze_task()  argument
168 	if (!freezing(p) || frozen(p) || __freeze_task(p)) {  in freeze_task()
173 	if (!(p->flags & PF_KTHREAD))  in freeze_task()
174 		fake_signal_wake_up(p);  in freeze_task()
176 		wake_up_state(p, TASK_NORMAL);  in freeze_task()
185  * here. For tasks which were TASK_NORMAL | TASK_FREEZABLE, their initial state
187  * Returns 1 if the task state was restored.
189 static int __restore_freezer_state(struct task_struct *p, void *arg)  in __restore_freezer_state()  argument
191 	unsigned int state = p->saved_state;  in __restore_freezer_state()  local
193 	if (state != TASK_RUNNING) {  in __restore_freezer_state()
194 		WRITE_ONCE(p->__state, state);  in __restore_freezer_state()
195 		p->saved_state = TASK_RUNNING;  in __restore_freezer_state()
202 void __thaw_task(struct task_struct *p)  in __thaw_task()  argument
207 	if (WARN_ON_ONCE(freezing(p)))  in __thaw_task()
210 	if (!frozen(p) || task_call_func(p, __restore_freezer_state, NULL))  in __thaw_task()
213 	wake_up_state(p, TASK_FROZEN);  in __thaw_task()
219  * set_freezable - make %current freezable
233 	current->flags &= ~PF_NOFREEZE;  in set_freezable()