1 files changed, 202 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
new file mode 100644
index 0000000..e377e22
--- /dev/null
+++ b/kernel/kthread.c
@@ -0,0 +1,202 @@
+/* Kernel thread helper functions.
+ *   Copyright (C) 2004 IBM Corporation, Rusty Russell.
+ *
+ * Creation is done via keventd, 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 <asm/semaphore.h>
+
+/*
+ * We dont want to execute off keventd since it might
+ * hold a semaphore our callers hold too:
+ */
+static struct workqueue_struct *helper_wq;
+
+struct kthread_create_info
+{
+	/* Information passed to kthread() from keventd. */
+	int (*threadfn)(void *data);
+	void *data;
+	struct completion started;
+
+	/* Result passed back to kthread_create() from keventd. */
+	struct task_struct *result;
+	struct completion done;
+};
+
+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 DECLARE_MUTEX(kthread_stop_lock);
+static struct kthread_stop_info kthread_stop_info;
+
+int kthread_should_stop(void)
+{
+	return (kthread_stop_info.k == current);
+}
+EXPORT_SYMBOL(kthread_should_stop);
+
+static void kthread_exit_files(void)
+{
+	struct fs_struct *fs;
+	struct task_struct *tsk = current;
+
+	exit_fs(tsk);		/* current->fs->count--; */
+	fs = init_task.fs;
+	tsk->fs = fs;
+	atomic_inc(&fs->count);
+ 	exit_files(tsk);
+	current->files = init_task.files;
+	atomic_inc(&tsk->files->count);
+}
+
+static int kthread(void *_create)
+{
+	struct kthread_create_info *create = _create;
+	int (*threadfn)(void *data);
+	void *data;
+	sigset_t blocked;
+	int ret = -EINTR;
+
+	kthread_exit_files();
+
+	/* Copy data: it's on keventd's stack */
+	threadfn = create->threadfn;
+	data = create->data;
+
+	/* Block and flush all signals (in case we're not from keventd). */
+	sigfillset(&blocked);
+	sigprocmask(SIG_BLOCK, &blocked, NULL);
+	flush_signals(current);
+
+	/* By default we can run anywhere, unlike keventd. */
+	set_cpus_allowed(current, CPU_MASK_ALL);
+
+	/* OK, tell user we're spawned, wait for stop or wakeup */
+	__set_current_state(TASK_INTERRUPTIBLE);
+	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;
+}
+
+/* We are keventd: create a thread. */
+static void keventd_create_kthread(void *_create)
+{
+	struct kthread_create_info *create = _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 {
+		wait_for_completion(&create->started);
+		create->result = find_task_by_pid(pid);
+	}
+	complete(&create->done);
+}
+
+struct task_struct *kthread_create(int (*threadfn)(void *data),
+				   void *data,
+				   const char namefmt[],
+				   ...)
+{
+	struct kthread_create_info create;
+	DECLARE_WORK(work, keventd_create_kthread, &create);
+
+	create.threadfn = threadfn;
+	create.data = data;
+	init_completion(&create.started);
+	init_completion(&create.done);
+
+	/*
+	 * The workqueue needs to start up first:
+	 */
+	if (!helper_wq)
+		work.func(work.data);
+	else {
+		queue_work(helper_wq, &work);
+		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);
+
+void kthread_bind(struct task_struct *k, unsigned int cpu)
+{
+	BUG_ON(k->state != TASK_INTERRUPTIBLE);
+	/* Must have done schedule() in kthread() before we set_task_cpu */
+	wait_task_inactive(k);
+	set_task_cpu(k, cpu);
+	k->cpus_allowed = cpumask_of_cpu(cpu);
+}
+EXPORT_SYMBOL(kthread_bind);
+
+int kthread_stop(struct task_struct *k)
+{
+	int ret;
+
+	down(&kthread_stop_lock);
+
+	/* It could exit after stop_info.k set, but before wake_up_process. */
+	get_task_struct(k);
+
+	/* Must init completion *before* thread sees kthread_stop_info.k */
+	init_completion(&kthread_stop_info.done);
+	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;
+	up(&kthread_stop_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(kthread_stop);
+
+static __init int helper_init(void)
+{
+	helper_wq = create_singlethread_workqueue("kthread");
+	BUG_ON(!helper_wq);
+
+	return 0;
+}
+core_initcall(helper_init);
+