1 files changed, 267 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
new file mode 100644
index 0000000..8e7a7ce
--- /dev/null
+++ b/kernel/kthread.c
@@ -0,0 +1,267 @@
+/* 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/unistd.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <trace/sched.h>
+
+#define KTHREAD_NICE_LEVEL (-5)
+
+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;
+	struct completion started;
+
+	/* Result passed back to kthread_create() from kthreadd. */
+	struct task_struct *result;
+	struct completion done;
+
+	struct list_head list;
+};
+
+struct kthread_stop_info
+{
+	struct task_struct *k;
+	int err;
+	struct completion done;
+};
+
+/* Thread stopping is done by setthing this var: lock serializes
+ * multiple kthread_stop calls. */
+static DEFINE_MUTEX(kthread_stop_lock);
+static struct kthread_stop_info kthread_stop_info;
+
+/**
+ * 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 (kthread_stop_info.k == current);
+}
+EXPORT_SYMBOL(kthread_should_stop);
+
+static int kthread(void *_create)
+{
+	struct kthread_create_info *create = _create;
+	int (*threadfn)(void *data);
+	void *data;
+	int ret = -EINTR;
+
+	/* Copy data: it's on kthread's stack */
+	threadfn = create->threadfn;
+	data = create->data;
+
+	/* OK, tell user we're spawned, wait for stop or wakeup */
+	__set_current_state(TASK_UNINTERRUPTIBLE);
+	complete(&create->started);
+	schedule();
+
+	if (!kthread_should_stop())
+		ret = threadfn(data);
+
+	/* It might have exited on its own, w/o kthread_stop.  Check. */
+	if (kthread_should_stop()) {
+		kthread_stop_info.err = ret;
+		complete(&kthread_stop_info.done);
+	}
+	return 0;
+}
+
+static void create_kthread(struct kthread_create_info *create)
+{
+	int pid;
+
+	/* 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);
+	} else {
+		struct sched_param param = { .sched_priority = 0 };
+		wait_for_completion(&create->started);
+		read_lock(&tasklist_lock);
+		create->result = find_task_by_pid_ns(pid, &init_pid_ns);
+		read_unlock(&tasklist_lock);
+		/*
+		 * root may have changed our (kthreadd's) priority or CPU mask.
+		 * The kernel thread should not inherit these properties.
+		 */
+		sched_setscheduler(create->result, SCHED_NORMAL, &param);
+		set_user_nice(create->result, KTHREAD_NICE_LEVEL);
+		set_cpus_allowed_ptr(create->result, CPU_MASK_ALL_PTR);
+	}
+	complete(&create->done);
+}
+
+/**
+ * kthread_create - create a kthread.
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @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(), kthread_create_on_cpu().
+ *
+ * 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 noone 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(int (*threadfn)(void *data),
+				   void *data,
+				   const char namefmt[],
+				   ...)
+{
+	struct kthread_create_info create;
+
+	create.threadfn = threadfn;
+	create.data = data;
+	init_completion(&create.started);
+	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)) {
+		va_list args;
+		va_start(args, namefmt);
+		vsnprintf(create.result->comm, sizeof(create.result->comm),
+			  namefmt, args);
+		va_end(args);
+	}
+	return create.result;
+}
+EXPORT_SYMBOL(kthread_create);
+
+/**
+ * kthread_bind - bind a just-created kthread to a cpu.
+ * @k: 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 *k, unsigned int cpu)
+{
+	/* Must have done schedule() in kthread() before we set_task_cpu */
+	if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
+		WARN_ON(1);
+		return;
+	}
+	set_task_cpu(k, cpu);
+	k->cpus_allowed = cpumask_of_cpu(cpu);
+	k->rt.nr_cpus_allowed = 1;
+	k->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.  Your threadfn() must not call do_exit()
+ * itself if you use this function!  This can also be called after
+ * kthread_create() instead of calling wake_up_process(): the thread
+ * will exit without calling threadfn().
+ *
+ * Returns the result of threadfn(), or %-EINTR if wake_up_process()
+ * was never called.
+ */
+int kthread_stop(struct task_struct *k)
+{
+	int ret;
+
+	mutex_lock(&kthread_stop_lock);
+
+	/* It could exit after stop_info.k set, but before wake_up_process. */
+	get_task_struct(k);
+
+	trace_sched_kthread_stop(k);
+
+	/* Must init completion *before* thread sees kthread_stop_info.k */
+	init_completion(&kthread_stop_info.done);
+	smp_wmb();
+
+	/* Now set kthread_should_stop() to true, and wake it up. */
+	kthread_stop_info.k = k;
+	wake_up_process(k);
+	put_task_struct(k);
+
+	/* Once it dies, reset stop ptr, gather result and we're done. */
+	wait_for_completion(&kthread_stop_info.done);
+	kthread_stop_info.k = NULL;
+	ret = kthread_stop_info.err;
+	mutex_unlock(&kthread_stop_lock);
+
+	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_user_nice(tsk, KTHREAD_NICE_LEVEL);
+	set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
+
+	current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
+
+	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;
+}