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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248// SPDX-License-Identifier: GPL-2.0-only/* * kernel/freezer.c - Function to freeze a process * * Originally from kernel/power/process.c */
#include <linux/interrupt.h>#include <linux/suspend.h>#include <linux/export.h>#include <linux/syscalls.h>#include <linux/freezer.h>#include <linux/oom.h>#include <linux/kthread.h>
/* total number of freezing conditions in effect */DEFINE_STATIC_KEY_FALSE(freezer_active);EXPORT_SYMBOL(freezer_active);
/* * indicate whether PM freezing is in effect, protected by * system_transition_mutex */bool pm_freezing;bool pm_nosig_freezing;
/* protects freezing and frozen transitions */static DEFINE_SPINLOCK(freezer_lock);
/** * freezing_slow_path - slow path for testing whether a task needs to be frozen * @p: task to be tested * * This function is called by freezing() if freezer_active isn't zero * and tests whether @p needs to enter and stay in frozen state. Can be * called under any context. The freezers are responsible for ensuring the * target tasks see the updated state. */bool freezing_slow_path(struct task_struct *p){ if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK)) return false;
if (tsk_is_oom_victim(p)) return false;
if (pm_nosig_freezing || cgroup1_freezing(p)) return true;
if (pm_freezing && !(p->flags & PF_KTHREAD)) return true;
return false;}EXPORT_SYMBOL(freezing_slow_path);
bool frozen(struct task_struct *p){ return READ_ONCE(p->__state) & TASK_FROZEN;}
/* Refrigerator is place where frozen processes are stored :-). */bool __refrigerator(bool check_kthr_stop){ unsigned int state = get_current_state(); bool was_frozen = false;
pr_debug("%s entered refrigerator\n", current->comm);
WARN_ON_ONCE(state && !(state & TASK_NORMAL));
for (;;) { bool freeze;
raw_spin_lock_irq(¤t->pi_lock); WRITE_ONCE(current->__state, TASK_FROZEN); /* unstale saved_state so that __thaw_task() will wake us up */ current->saved_state = TASK_RUNNING; raw_spin_unlock_irq(¤t->pi_lock);
spin_lock_irq(&freezer_lock); freeze = freezing(current) && !(check_kthr_stop && kthread_should_stop()); spin_unlock_irq(&freezer_lock);
if (!freeze) break;
was_frozen = true; schedule(); } __set_current_state(TASK_RUNNING);
pr_debug("%s left refrigerator\n", current->comm);
return was_frozen;}EXPORT_SYMBOL(__refrigerator);
static void fake_signal_wake_up(struct task_struct *p){ unsigned long flags;
if (lock_task_sighand(p, &flags)) { signal_wake_up(p, 0); unlock_task_sighand(p, &flags); }}
static int __set_task_frozen(struct task_struct *p, void *arg){ unsigned int state = READ_ONCE(p->__state);
/* * Allow freezing the sched_delayed tasks; they will not execute until * ttwu() fixes them up, so it is safe to swap their state now, instead * of waiting for them to get fully dequeued. */ if (task_is_runnable(p)) return 0;
if (p != current && task_curr(p)) return 0;
if (!(state & (TASK_FREEZABLE | __TASK_STOPPED | __TASK_TRACED))) return 0;
/* * Only TASK_NORMAL can be augmented with TASK_FREEZABLE, since they * can suffer spurious wakeups. */ if (state & TASK_FREEZABLE) WARN_ON_ONCE(!(state & TASK_NORMAL));
#ifdef CONFIG_LOCKDEP /* * It's dangerous to freeze with locks held; there be dragons there. */ if (!(state & __TASK_FREEZABLE_UNSAFE)) WARN_ON_ONCE(debug_locks && p->lockdep_depth);#endif
p->saved_state = p->__state; WRITE_ONCE(p->__state, TASK_FROZEN); return TASK_FROZEN;}
static bool __freeze_task(struct task_struct *p){ /* TASK_FREEZABLE|TASK_STOPPED|TASK_TRACED -> TASK_FROZEN */ return task_call_func(p, __set_task_frozen, NULL);}
/** * freeze_task - send a freeze request to given task * @p: task to send the request to * * If @p is freezing, the freeze request is sent either by sending a fake * signal (if it's not a kernel thread) or waking it up (if it's a kernel * thread). * * RETURNS: * %false, if @p is not freezing or already frozen; %true, otherwise */bool freeze_task(struct task_struct *p){ unsigned long flags;
spin_lock_irqsave(&freezer_lock, flags); if (!freezing(p) || frozen(p) || __freeze_task(p)) { spin_unlock_irqrestore(&freezer_lock, flags); return false; }
if (!(p->flags & PF_KTHREAD)) fake_signal_wake_up(p); else wake_up_state(p, TASK_NORMAL);
spin_unlock_irqrestore(&freezer_lock, flags); return true;}
/* * Restore the saved_state before the task entered freezer. For typical task * in the __refrigerator(), saved_state == TASK_RUNNING so nothing happens * here. For tasks which were TASK_NORMAL | TASK_FREEZABLE, their initial state * is restored unless they got an expected wakeup (see ttwu_state_match()). * Returns 1 if the task state was restored. */static int __restore_freezer_state(struct task_struct *p, void *arg){ unsigned int state = p->saved_state;
if (state != TASK_RUNNING) { WRITE_ONCE(p->__state, state); p->saved_state = TASK_RUNNING; return 1; }
return 0;}
void __thaw_task(struct task_struct *p){ guard(spinlock_irqsave)(&freezer_lock); if (frozen(p) && !task_call_func(p, __restore_freezer_state, NULL)) wake_up_state(p, TASK_FROZEN);}
/* * thaw_process - Thaw a frozen process * @p: the process to be thawed * * Iterate over all threads of @p and call __thaw_task() on each. */void thaw_process(struct task_struct *p){ struct task_struct *t;
rcu_read_lock(); for_each_thread(p, t) { __thaw_task(t); } rcu_read_unlock();}
/** * set_freezable - make %current freezable * * Mark %current freezable and enter refrigerator if necessary. */bool set_freezable(void){ might_sleep();
/* * Modify flags while holding freezer_lock. This ensures the * freezer notices that we aren't frozen yet or the freezing * condition is visible to try_to_freeze() below. */ spin_lock_irq(&freezer_lock); current->flags &= ~PF_NOFREEZE; spin_unlock_irq(&freezer_lock);
return try_to_freeze();}EXPORT_SYMBOL(set_freezable);