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235 lines
5.4 KiB
235 lines
5.4 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* kernel/freezer.c - Function to freeze a process |
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* |
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* Originally from kernel/power/process.c |
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*/ |
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#include <linux/interrupt.h> |
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#include <linux/suspend.h> |
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#include <linux/export.h> |
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#include <linux/syscalls.h> |
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#include <linux/freezer.h> |
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#include <linux/kthread.h> |
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/* total number of freezing conditions in effect */ |
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DEFINE_STATIC_KEY_FALSE(freezer_active); |
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EXPORT_SYMBOL(freezer_active); |
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/* |
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* indicate whether PM freezing is in effect, protected by |
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* system_transition_mutex |
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*/ |
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bool pm_freezing; |
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bool pm_nosig_freezing; |
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/* protects freezing and frozen transitions */ |
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static DEFINE_SPINLOCK(freezer_lock); |
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/** |
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* freezing_slow_path - slow path for testing whether a task needs to be frozen |
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* @p: task to be tested |
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* |
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* This function is called by freezing() if freezer_active isn't zero |
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* and tests whether @p needs to enter and stay in frozen state. Can be |
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* called under any context. The freezers are responsible for ensuring the |
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* target tasks see the updated state. |
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*/ |
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bool freezing_slow_path(struct task_struct *p) |
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{ |
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if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK)) |
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return false; |
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if (test_tsk_thread_flag(p, TIF_MEMDIE)) |
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return false; |
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if (pm_nosig_freezing || cgroup_freezing(p)) |
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return true; |
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if (pm_freezing && !(p->flags & PF_KTHREAD)) |
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return true; |
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return false; |
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} |
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EXPORT_SYMBOL(freezing_slow_path); |
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bool frozen(struct task_struct *p) |
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{ |
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return READ_ONCE(p->__state) & TASK_FROZEN; |
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} |
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/* Refrigerator is place where frozen processes are stored :-). */ |
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bool __refrigerator(bool check_kthr_stop) |
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{ |
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unsigned int state = get_current_state(); |
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bool was_frozen = false; |
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pr_debug("%s entered refrigerator\n", current->comm); |
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WARN_ON_ONCE(state && !(state & TASK_NORMAL)); |
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for (;;) { |
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bool freeze; |
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set_current_state(TASK_FROZEN); |
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spin_lock_irq(&freezer_lock); |
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freeze = freezing(current) && !(check_kthr_stop && kthread_should_stop()); |
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spin_unlock_irq(&freezer_lock); |
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if (!freeze) |
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break; |
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was_frozen = true; |
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schedule(); |
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} |
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__set_current_state(TASK_RUNNING); |
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pr_debug("%s left refrigerator\n", current->comm); |
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return was_frozen; |
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} |
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EXPORT_SYMBOL(__refrigerator); |
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static void fake_signal_wake_up(struct task_struct *p) |
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{ |
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unsigned long flags; |
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if (lock_task_sighand(p, &flags)) { |
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signal_wake_up(p, 0); |
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unlock_task_sighand(p, &flags); |
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} |
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} |
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static int __set_task_frozen(struct task_struct *p, void *arg) |
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{ |
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unsigned int state = READ_ONCE(p->__state); |
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if (p->on_rq) |
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return 0; |
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if (p != current && task_curr(p)) |
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return 0; |
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if (!(state & (TASK_FREEZABLE | __TASK_STOPPED | __TASK_TRACED))) |
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return 0; |
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/* |
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* Only TASK_NORMAL can be augmented with TASK_FREEZABLE, since they |
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* can suffer spurious wakeups. |
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*/ |
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if (state & TASK_FREEZABLE) |
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WARN_ON_ONCE(!(state & TASK_NORMAL)); |
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#ifdef CONFIG_LOCKDEP |
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/* |
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* It's dangerous to freeze with locks held; there be dragons there. |
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*/ |
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if (!(state & __TASK_FREEZABLE_UNSAFE)) |
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WARN_ON_ONCE(debug_locks && p->lockdep_depth); |
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#endif |
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WRITE_ONCE(p->__state, TASK_FROZEN); |
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return TASK_FROZEN; |
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} |
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static bool __freeze_task(struct task_struct *p) |
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{ |
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/* TASK_FREEZABLE|TASK_STOPPED|TASK_TRACED -> TASK_FROZEN */ |
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return task_call_func(p, __set_task_frozen, NULL); |
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} |
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/** |
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* freeze_task - send a freeze request to given task |
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* @p: task to send the request to |
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* |
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* If @p is freezing, the freeze request is sent either by sending a fake |
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* signal (if it's not a kernel thread) or waking it up (if it's a kernel |
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* thread). |
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* |
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* RETURNS: |
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* %false, if @p is not freezing or already frozen; %true, otherwise |
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*/ |
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bool freeze_task(struct task_struct *p) |
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{ |
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unsigned long flags; |
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spin_lock_irqsave(&freezer_lock, flags); |
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if (!freezing(p) || frozen(p) || __freeze_task(p)) { |
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spin_unlock_irqrestore(&freezer_lock, flags); |
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return false; |
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} |
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if (!(p->flags & PF_KTHREAD)) |
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fake_signal_wake_up(p); |
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else |
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wake_up_state(p, TASK_NORMAL); |
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spin_unlock_irqrestore(&freezer_lock, flags); |
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return true; |
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} |
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/* |
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* The special task states (TASK_STOPPED, TASK_TRACED) keep their canonical |
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* state in p->jobctl. If either of them got a wakeup that was missed because |
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* TASK_FROZEN, then their canonical state reflects that and the below will |
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* refuse to restore the special state and instead issue the wakeup. |
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*/ |
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static int __set_task_special(struct task_struct *p, void *arg) |
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{ |
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unsigned int state = 0; |
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if (p->jobctl & JOBCTL_TRACED) |
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state = TASK_TRACED; |
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else if (p->jobctl & JOBCTL_STOPPED) |
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state = TASK_STOPPED; |
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if (state) |
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WRITE_ONCE(p->__state, state); |
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return state; |
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} |
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void __thaw_task(struct task_struct *p) |
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{ |
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unsigned long flags, flags2; |
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spin_lock_irqsave(&freezer_lock, flags); |
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if (WARN_ON_ONCE(freezing(p))) |
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goto unlock; |
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if (lock_task_sighand(p, &flags2)) { |
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/* TASK_FROZEN -> TASK_{STOPPED,TRACED} */ |
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bool ret = task_call_func(p, __set_task_special, NULL); |
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unlock_task_sighand(p, &flags2); |
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if (ret) |
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goto unlock; |
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} |
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wake_up_state(p, TASK_FROZEN); |
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unlock: |
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spin_unlock_irqrestore(&freezer_lock, flags); |
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} |
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/** |
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* set_freezable - make %current freezable |
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* |
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* Mark %current freezable and enter refrigerator if necessary. |
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*/ |
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bool set_freezable(void) |
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{ |
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might_sleep(); |
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/* |
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* Modify flags while holding freezer_lock. This ensures the |
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* freezer notices that we aren't frozen yet or the freezing |
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* condition is visible to try_to_freeze() below. |
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*/ |
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spin_lock_irq(&freezer_lock); |
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current->flags &= ~PF_NOFREEZE; |
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spin_unlock_irq(&freezer_lock); |
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return try_to_freeze(); |
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} |
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EXPORT_SYMBOL(set_freezable);
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