--- /dev/null
+/*
+ * 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);
Code Review / kvmfornfv.git / blobdiff