1 files changed, 484 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
new file mode 100644
index 00000000..b579af57
--- /dev/null
+++ b/kernel/kthread.c
@@ -0,0 +1,484 @@
+/* Kernel thread helper functions.
+ *   Copyright (C) 2004 IBM Corporation, Rusty Russell.
+ *
+ * Creation is done via kthreadd, so that we get a clean environment
+ * even if we're invoked from userspace (think modprobe, hotplug cpu,
+ * etc.).
+ */
+#include <linux/sched.h>
+#include <linux/kthread.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/cpuset.h>
+#include <linux/unistd.h>
+#include <linux/file.h>
+#include <linux/export.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/freezer.h>
+#include <trace/events/sched.h>
+
+static DEFINE_SPINLOCK(kthread_create_lock);
+static LIST_HEAD(kthread_create_list);
+struct task_struct *kthreadd_task;
+
+struct kthread_create_info
+{
+	/* Information passed to kthread() from kthreadd. */
+	int (*threadfn)(void *data);
+	void *data;
+	int node;
+
+	/* Result passed back to kthread_create() from kthreadd. */
+	struct task_struct *result;
+	struct completion done;
+
+	struct list_head list;
+};
+
+struct kthread {
+	int should_stop;
+	void *data;
+	struct completion exited;
+};
+
+#define to_kthread(tsk)	\
+	container_of((tsk)->vfork_done, struct kthread, exited)
+
+/**
+ * kthread_should_stop - should this kthread return now?
+ *
+ * When someone calls kthread_stop() on your kthread, it will be woken
+ * and this will return true.  You should then return, and your return
+ * value will be passed through to kthread_stop().
+ */
+int kthread_should_stop(void)
+{
+	return to_kthread(current)->should_stop;
+}
+EXPORT_SYMBOL(kthread_should_stop);
+
+/**
+ * kthread_freezable_should_stop - should this freezable kthread return now?
+ * @was_frozen: optional out parameter, indicates whether %current was frozen
+ *
+ * kthread_should_stop() for freezable kthreads, which will enter
+ * refrigerator if necessary.  This function is safe from kthread_stop() /
+ * freezer deadlock and freezable kthreads should use this function instead
+ * of calling try_to_freeze() directly.
+ */
+bool kthread_freezable_should_stop(bool *was_frozen)
+{
+	bool frozen = false;
+
+	might_sleep();
+
+	if (unlikely(freezing(current)))
+		frozen = __refrigerator(true);
+
+	if (was_frozen)
+		*was_frozen = frozen;
+
+	return kthread_should_stop();
+}
+EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
+
+/**
+ * kthread_data - return data value specified on kthread creation
+ * @task: kthread task in question
+ *
+ * Return the data value specified when kthread @task was created.
+ * The caller is responsible for ensuring the validity of @task when
+ * calling this function.
+ */
+void *kthread_data(struct task_struct *task)
+{
+	return to_kthread(task)->data;
+}
+
+static int kthread(void *_create)
+{
+	/* Copy data: it's on kthread's stack */
+	struct kthread_create_info *create = _create;
+	int (*threadfn)(void *data) = create->threadfn;
+	void *data = create->data;
+	struct kthread self;
+	int ret;
+
+	self.should_stop = 0;
+	self.data = data;
+	init_completion(&self.exited);
+	current->vfork_done = &self.exited;
+
+	/* OK, tell user we're spawned, wait for stop or wakeup */
+	__set_current_state(TASK_UNINTERRUPTIBLE);
+	create->result = current;
+	complete(&create->done);
+	schedule();
+
+	ret = -EINTR;
+	if (!self.should_stop)
+		ret = threadfn(data);
+
+	/* we can't just return, we must preserve "self" on stack */
+	do_exit(ret);
+}
+
+/* called from do_fork() to get node information for about to be created task */
+int tsk_fork_get_node(struct task_struct *tsk)
+{
+#ifdef CONFIG_NUMA
+	if (tsk == kthreadd_task)
+		return tsk->pref_node_fork;
+#endif
+	return numa_node_id();
+}
+
+static void create_kthread(struct kthread_create_info *create)
+{
+	int pid;
+
+#ifdef CONFIG_NUMA
+	current->pref_node_fork = create->node;
+#endif
+	/* We want our own signal handler (we take no signals by default). */
+	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
+	if (pid < 0) {
+		create->result = ERR_PTR(pid);
+		complete(&create->done);
+	}
+}
+
+/**
+ * kthread_create_on_node - create a kthread.
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @node: memory node number.
+ * @namefmt: printf-style name for the thread.
+ *
+ * Description: This helper function creates and names a kernel
+ * thread.  The thread will be stopped: use wake_up_process() to start
+ * it.  See also kthread_run().
+ *
+ * If thread is going to be bound on a particular cpu, give its node
+ * in @node, to get NUMA affinity for kthread stack, or else give -1.
+ * When woken, the thread will run @threadfn() with @data as its
+ * argument. @threadfn() can either call do_exit() directly if it is a
+ * standalone thread for which no one will call kthread_stop(), or
+ * return when 'kthread_should_stop()' is true (which means
+ * kthread_stop() has been called).  The return value should be zero
+ * or a negative error number; it will be passed to kthread_stop().
+ *
+ * Returns a task_struct or ERR_PTR(-ENOMEM).
+ */
+struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
+					   void *data,
+					   int node,
+					   const char namefmt[],
+					   ...)
+{
+	struct kthread_create_info create;
+
+	create.threadfn = threadfn;
+	create.data = data;
+	create.node = node;
+	init_completion(&create.done);
+
+	spin_lock(&kthread_create_lock);
+	list_add_tail(&create.list, &kthread_create_list);
+	spin_unlock(&kthread_create_lock);
+
+	wake_up_process(kthreadd_task);
+	wait_for_completion(&create.done);
+
+	if (!IS_ERR(create.result)) {
+		static const struct sched_param param = { .sched_priority = 0 };
+		va_list args;
+
+		va_start(args, namefmt);
+		vsnprintf(create.result->comm, sizeof(create.result->comm),
+			  namefmt, args);
+		va_end(args);
+		/*
+		 * root may have changed our (kthreadd's) priority or CPU mask.
+		 * The kernel thread should not inherit these properties.
+		 */
+		sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
+		set_cpus_allowed_ptr(create.result, cpu_all_mask);
+	}
+	return create.result;
+}
+EXPORT_SYMBOL(kthread_create_on_node);
+
+/**
+ * kthread_bind - bind a just-created kthread to a cpu.
+ * @p: thread created by kthread_create().
+ * @cpu: cpu (might not be online, must be possible) for @k to run on.
+ *
+ * Description: This function is equivalent to set_cpus_allowed(),
+ * except that @cpu doesn't need to be online, and the thread must be
+ * stopped (i.e., just returned from kthread_create()).
+ */
+void kthread_bind(struct task_struct *p, unsigned int cpu)
+{
+	/* Must have done schedule() in kthread() before we set_task_cpu */
+	if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
+		WARN_ON(1);
+		return;
+	}
+
+	/* It's safe because the task is inactive. */
+	do_set_cpus_allowed(p, cpumask_of(cpu));
+	p->flags |= PF_THREAD_BOUND;
+}
+EXPORT_SYMBOL(kthread_bind);
+
+/**
+ * kthread_stop - stop a thread created by kthread_create().
+ * @k: thread created by kthread_create().
+ *
+ * Sets kthread_should_stop() for @k to return true, wakes it, and
+ * waits for it to exit. This can also be called after kthread_create()
+ * instead of calling wake_up_process(): the thread will exit without
+ * calling threadfn().
+ *
+ * If threadfn() may call do_exit() itself, the caller must ensure
+ * task_struct can't go away.
+ *
+ * Returns the result of threadfn(), or %-EINTR if wake_up_process()
+ * was never called.
+ */
+int kthread_stop(struct task_struct *k)
+{
+	struct kthread *kthread;
+	int ret;
+
+	trace_sched_kthread_stop(k);
+	get_task_struct(k);
+
+	kthread = to_kthread(k);
+	barrier(); /* it might have exited */
+	if (k->vfork_done != NULL) {
+		kthread->should_stop = 1;
+		wake_up_process(k);
+		wait_for_completion(&kthread->exited);
+	}
+	ret = k->exit_code;
+
+	put_task_struct(k);
+	trace_sched_kthread_stop_ret(ret);
+
+	return ret;
+}
+EXPORT_SYMBOL(kthread_stop);
+
+int kthreadd(void *unused)
+{
+	struct task_struct *tsk = current;
+
+	/* Setup a clean context for our children to inherit. */
+	set_task_comm(tsk, "kthreadd");
+	ignore_signals(tsk);
+	set_cpus_allowed_ptr(tsk, cpu_all_mask);
+	set_mems_allowed(node_states[N_HIGH_MEMORY]);
+
+	current->flags |= PF_NOFREEZE;
+
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (list_empty(&kthread_create_list))
+			schedule();
+		__set_current_state(TASK_RUNNING);
+
+		spin_lock(&kthread_create_lock);
+		while (!list_empty(&kthread_create_list)) {
+			struct kthread_create_info *create;
+
+			create = list_entry(kthread_create_list.next,
+					    struct kthread_create_info, list);
+			list_del_init(&create->list);
+			spin_unlock(&kthread_create_lock);
+
+			create_kthread(create);
+
+			spin_lock(&kthread_create_lock);
+		}
+		spin_unlock(&kthread_create_lock);
+	}
+
+	return 0;
+}
+
+void __init_kthread_worker(struct kthread_worker *worker,
+				const char *name,
+				struct lock_class_key *key)
+{
+	spin_lock_init(&worker->lock);
+	lockdep_set_class_and_name(&worker->lock, key, name);
+	INIT_LIST_HEAD(&worker->work_list);
+	worker->task = NULL;
+}
+EXPORT_SYMBOL_GPL(__init_kthread_worker);
+
+/**
+ * kthread_worker_fn - kthread function to process kthread_worker
+ * @worker_ptr: pointer to initialized kthread_worker
+ *
+ * This function can be used as @threadfn to kthread_create() or
+ * kthread_run() with @worker_ptr argument pointing to an initialized
+ * kthread_worker.  The started kthread will process work_list until
+ * the it is stopped with kthread_stop().  A kthread can also call
+ * this function directly after extra initialization.
+ *
+ * Different kthreads can be used for the same kthread_worker as long
+ * as there's only one kthread attached to it at any given time.  A
+ * kthread_worker without an attached kthread simply collects queued
+ * kthread_works.
+ */
+int kthread_worker_fn(void *worker_ptr)
+{
+	struct kthread_worker *worker = worker_ptr;
+	struct kthread_work *work;
+
+	WARN_ON(worker->task);
+	worker->task = current;
+repeat:
+	set_current_state(TASK_INTERRUPTIBLE);	/* mb paired w/ kthread_stop */
+
+	if (kthread_should_stop()) {
+		__set_current_state(TASK_RUNNING);
+		spin_lock_irq(&worker->lock);
+		worker->task = NULL;
+		spin_unlock_irq(&worker->lock);
+		return 0;
+	}
+
+	work = NULL;
+	spin_lock_irq(&worker->lock);
+	if (!list_empty(&worker->work_list)) {
+		work = list_first_entry(&worker->work_list,
+					struct kthread_work, node);
+		list_del_init(&work->node);
+	}
+	worker->current_work = work;
+	spin_unlock_irq(&worker->lock);
+
+	if (work) {
+		__set_current_state(TASK_RUNNING);
+		work->func(work);
+	} else if (!freezing(current))
+		schedule();
+
+	try_to_freeze();
+	goto repeat;
+}
+EXPORT_SYMBOL_GPL(kthread_worker_fn);
+
+/* insert @work before @pos in @worker */
+static void insert_kthread_work(struct kthread_worker *worker,
+			       struct kthread_work *work,
+			       struct list_head *pos)
+{
+	lockdep_assert_held(&worker->lock);
+
+	list_add_tail(&work->node, pos);
+	work->worker = worker;
+	if (likely(worker->task))
+		wake_up_process(worker->task);
+}
+
+/**
+ * queue_kthread_work - queue a kthread_work
+ * @worker: target kthread_worker
+ * @work: kthread_work to queue
+ *
+ * Queue @work to work processor @task for async execution.  @task
+ * must have been created with kthread_worker_create().  Returns %true
+ * if @work was successfully queued, %false if it was already pending.
+ */
+bool queue_kthread_work(struct kthread_worker *worker,
+			struct kthread_work *work)
+{
+	bool ret = false;
+	unsigned long flags;
+
+	spin_lock_irqsave(&worker->lock, flags);
+	if (list_empty(&work->node)) {
+		insert_kthread_work(worker, work, &worker->work_list);
+		ret = true;
+	}
+	spin_unlock_irqrestore(&worker->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(queue_kthread_work);
+
+struct kthread_flush_work {
+	struct kthread_work	work;
+	struct completion	done;
+};
+
+static void kthread_flush_work_fn(struct kthread_work *work)
+{
+	struct kthread_flush_work *fwork =
+		container_of(work, struct kthread_flush_work, work);
+	complete(&fwork->done);
+}
+
+/**
+ * flush_kthread_work - flush a kthread_work
+ * @work: work to flush
+ *
+ * If @work is queued or executing, wait for it to finish execution.
+ */
+void flush_kthread_work(struct kthread_work *work)
+{
+	struct kthread_flush_work fwork = {
+		KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
+		COMPLETION_INITIALIZER_ONSTACK(fwork.done),
+	};
+	struct kthread_worker *worker;
+	bool noop = false;
+
+retry:
+	worker = work->worker;
+	if (!worker)
+		return;
+
+	spin_lock_irq(&worker->lock);
+	if (work->worker != worker) {
+		spin_unlock_irq(&worker->lock);
+		goto retry;
+	}
+
+	if (!list_empty(&work->node))
+		insert_kthread_work(worker, &fwork.work, work->node.next);
+	else if (worker->current_work == work)
+		insert_kthread_work(worker, &fwork.work, worker->work_list.next);
+	else
+		noop = true;
+
+	spin_unlock_irq(&worker->lock);
+
+	if (!noop)
+		wait_for_completion(&fwork.done);
+}
+EXPORT_SYMBOL_GPL(flush_kthread_work);
+
+/**
+ * flush_kthread_worker - flush all current works on a kthread_worker
+ * @worker: worker to flush
+ *
+ * Wait until all currently executing or pending works on @worker are
+ * finished.
+ */
+void flush_kthread_worker(struct kthread_worker *worker)
+{
+	struct kthread_flush_work fwork = {
+		KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
+		COMPLETION_INITIALIZER_ONSTACK(fwork.done),
+	};
+
+	queue_kthread_work(worker, &fwork.work);
+	wait_for_completion(&fwork.done);
+}
+EXPORT_SYMBOL_GPL(flush_kthread_worker);