cregit-Linux how code gets into the kernel

Release 4.15 kernel/freezer.c

Directory: kernel
/*
 * 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/kthread.h>

/* total number of freezing conditions in effect */

atomic_t system_freezing_cnt = ATOMIC_INIT(0);

EXPORT_SYMBOL(system_freezing_cnt);

/* indicate whether PM freezing is in effect, protected by pm_mutex */

bool pm_freezing;

bool pm_nosig_freezing;

/*
 * Temporary export for the deadlock workaround in ata_scsi_hotplug().
 * Remove once the hack becomes unnecessary.
 */

EXPORT_SYMBOL_GPL(pm_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 system_freezing_cnt 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 (test_tsk_thread_flag(p, TIF_MEMDIE)) return false; if (pm_nosig_freezing || cgroup_freezing(p)) return true; if (pm_freezing && !(p->flags & PF_KTHREAD)) return true; return false; }

Contributors

PersonTokensPropCommitsCommitProp
Tejun Heo5276.47%240.00%
Américo Wang913.24%120.00%
Colin Cross45.88%120.00%
Michal Hocko34.41%120.00%
Total68100.00%5100.00%

EXPORT_SYMBOL(freezing_slow_path); /* Refrigerator is place where frozen processes are stored :-). */
bool __refrigerator(bool check_kthr_stop) { /* Hmm, should we be allowed to suspend when there are realtime processes around? */ bool was_frozen = false; long save = current->state; pr_debug("%s entered refrigerator\n", current->comm); for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); spin_lock_irq(&freezer_lock); current->flags |= PF_FROZEN; if (!freezing(current) || (check_kthr_stop && kthread_should_stop())) current->flags &= ~PF_FROZEN; spin_unlock_irq(&freezer_lock); if (!(current->flags & PF_FROZEN)) break; was_frozen = true; schedule(); } pr_debug("%s left refrigerator\n", current->comm); /* * Restore saved task state before returning. The mb'd version * needs to be used; otherwise, it might silently break * synchronization which depends on ordered task state change. */ set_current_state(save); return was_frozen; }

Contributors

PersonTokensPropCommitsCommitProp
Tejun Heo6453.78%583.33%
Matt Helsley5546.22%116.67%
Total119100.00%6100.00%

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); } }

Contributors

PersonTokensPropCommitsCommitProp
Matt Helsley3276.19%133.33%
Tejun Heo1023.81%266.67%
Total42100.00%3100.00%

/** * 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; /* * This check can race with freezer_do_not_count, but worst case that * will result in an extra wakeup being sent to the task. It does not * race with freezer_count(), the barriers in freezer_count() and * freezer_should_skip() ensure that either freezer_count() sees * freezing == true in try_to_freeze() and freezes, or * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task * normally. */ if (freezer_should_skip(p)) return false; spin_lock_irqsave(&freezer_lock, flags); if (!freezing(p) || frozen(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_INTERRUPTIBLE); spin_unlock_irqrestore(&freezer_lock, flags); return true; }

Contributors

PersonTokensPropCommitsCommitProp
Matt Helsley4345.74%116.67%
Tejun Heo4042.55%466.67%
Colin Cross1111.70%116.67%
Total94100.00%6100.00%


void __thaw_task(struct task_struct *p) { unsigned long flags; spin_lock_irqsave(&freezer_lock, flags); if (frozen(p)) wake_up_process(p); spin_unlock_irqrestore(&freezer_lock, flags); }

Contributors

PersonTokensPropCommitsCommitProp
Matt Helsley2764.29%133.33%
Tejun Heo1535.71%266.67%
Total42100.00%3100.00%

/** * 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(); }

Contributors

PersonTokensPropCommitsCommitProp
Tejun Heo34100.00%2100.00%
Total34100.00%2100.00%

EXPORT_SYMBOL(set_freezable);

Overall Contributors

PersonTokensPropCommitsCommitProp
Tejun Heo26155.41%1466.67%
Matt Helsley18138.43%14.76%
Colin Cross153.18%29.52%
Américo Wang91.91%14.76%
Michal Hocko30.64%14.76%
Paul Gortmaker10.21%14.76%
Marcos Paulo de Souza10.21%14.76%
Total471100.00%21100.00%
Directory: kernel
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