1 // SPDX-License-Identifier: GPL-2.0-only
3 * kernel/freezer.c - Function to freeze a process
5 * Originally from kernel/power/process.c
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>
16 #include <linux/ksm.h>
19 /* total number of freezing conditions in effect */
20 atomic_t system_freezing_cnt = ATOMIC_INIT(0);
21 EXPORT_SYMBOL(system_freezing_cnt);
23 /* indicate whether PM freezing is in effect, protected by
24 * system_transition_mutex
27 bool pm_nosig_freezing;
29 /* protects freezing and frozen transitions */
30 static DEFINE_SPINLOCK(freezer_lock);
33 * freezing_slow_path - slow path for testing whether a task needs to be frozen
34 * @p: task to be tested
36 * This function is called by freezing() if system_freezing_cnt isn't zero
37 * and tests whether @p needs to enter and stay in frozen state. Can be
38 * called under any context. The freezers are responsible for ensuring the
39 * target tasks see the updated state.
41 bool freezing_slow_path(struct task_struct *p)
43 if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK))
46 if (test_tsk_thread_flag(p, TIF_MEMDIE))
49 if (pm_nosig_freezing || cgroup_freezing(p))
52 if (pm_freezing && !(p->flags & PF_KTHREAD))
57 EXPORT_SYMBOL(freezing_slow_path);
59 /* Refrigerator is place where frozen processes are stored :-). */
60 bool __refrigerator(bool check_kthr_stop)
62 /* Hmm, should we be allowed to suspend when there are realtime
64 bool was_frozen = false;
65 unsigned int save = get_current_state();
67 pr_debug("%s entered refrigerator\n", current->comm);
70 set_current_state(TASK_UNINTERRUPTIBLE);
72 spin_lock_irq(&freezer_lock);
73 current->flags |= PF_FROZEN;
74 if (!freezing(current) ||
75 (check_kthr_stop && kthread_should_stop()))
76 current->flags &= ~PF_FROZEN;
77 spin_unlock_irq(&freezer_lock);
79 if (!(current->flags & PF_FROZEN))
85 pr_debug("%s left refrigerator\n", current->comm);
88 * Restore saved task state before returning. The mb'd version
89 * needs to be used; otherwise, it might silently break
90 * synchronization which depends on ordered task state change.
92 set_current_state(save);
96 EXPORT_SYMBOL(__refrigerator);
98 static void fake_signal_wake_up(struct task_struct *p)
102 if (lock_task_sighand(p, &flags)) {
103 signal_wake_up(p, 0);
104 unlock_task_sighand(p, &flags);
109 * freeze_task - send a freeze request to given task
110 * @p: task to send the request to
112 * If @p is freezing, the freeze request is sent either by sending a fake
113 * signal (if it's not a kernel thread) or waking it up (if it's a kernel
117 * %false, if @p is not freezing or already frozen; %true, otherwise
119 bool freeze_task(struct task_struct *p)
124 * This check can race with freezer_do_not_count, but worst case that
125 * will result in an extra wakeup being sent to the task. It does not
126 * race with freezer_count(), the barriers in freezer_count() and
127 * freezer_should_skip() ensure that either freezer_count() sees
128 * freezing == true in try_to_freeze() and freezes, or
129 * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
132 if (freezer_should_skip(p))
135 spin_lock_irqsave(&freezer_lock, flags);
136 if (!freezing(p) || frozen(p)) {
137 spin_unlock_irqrestore(&freezer_lock, flags);
141 if (!(p->flags & PF_KTHREAD))
142 fake_signal_wake_up(p);
144 wake_up_state(p, TASK_INTERRUPTIBLE);
146 spin_unlock_irqrestore(&freezer_lock, flags);
148 if (!(p->flags & PF_KTHREAD))
149 lksm_hint(p, KSM_TASK_FROZEN);
154 void __thaw_task(struct task_struct *p)
158 spin_lock_irqsave(&freezer_lock, flags);
161 spin_unlock_irqrestore(&freezer_lock, flags);
163 if (!(p->flags & PF_KTHREAD))
164 lksm_hint(p, KSM_TASK_THAWED);
169 * set_freezable - make %current freezable
171 * Mark %current freezable and enter refrigerator if necessary.
173 bool set_freezable(void)
178 * Modify flags while holding freezer_lock. This ensures the
179 * freezer notices that we aren't frozen yet or the freezing
180 * condition is visible to try_to_freeze() below.
182 spin_lock_irq(&freezer_lock);
183 current->flags &= ~PF_NOFREEZE;
184 spin_unlock_irq(&freezer_lock);
186 return try_to_freeze();
188 EXPORT_SYMBOL(set_freezable);