From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 kernel/freezer.c | 179 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 179 insertions(+)
 create mode 100644 kernel/freezer.c

(limited to 'kernel/freezer.c')

diff --git a/kernel/freezer.c b/kernel/freezer.c
new file mode 100644
index 000000000..a8900a3bc
--- /dev/null
+++ b/kernel/freezer.c
@@ -0,0 +1,179 @@
+/*
+ * 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_thread_flag(TIF_MEMDIE))
+		return false;
+
+	if (pm_nosig_freezing || cgroup_freezing(p))
+		return true;
+
+	if (pm_freezing && !(p->flags & PF_KTHREAD))
+		return true;
+
+	return false;
+}
+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;
+}
+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);
+	}
+}
+
+/**
+ * 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;
+}
+
+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);
+}
+
+/**
+ * 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);
-- 
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