1 files changed, 103 insertions, 10 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 36fd751..12695e6 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -571,23 +571,24 @@ EXPORT_SYMBOL_GPL(__kthread_init_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.
+ * This function implements the main cycle of kthread worker. It processes
+ * work_list until it is stopped with kthread_stop(). It sleeps when the queue
+ * is empty.
  *
- * 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.
+ * The works are not allowed to keep any locks, disable preemption or interrupts
+ * when they finish. There is defined a safe point for freezing when one work
+ * finishes and before a new one is started.
  */
 int kthread_worker_fn(void *worker_ptr)
 {
 	struct kthread_worker *worker = worker_ptr;
 	struct kthread_work *work;
 
-	WARN_ON(worker->task);
+	/*
+	 * FIXME: Update the check and remove the assignment when all kthread
+	 * worker users are created using kthread_create_worker*() functions.
+	 */
+	WARN_ON(worker->task && worker->task != current);
 	worker->task = current;
 repeat:
 	set_current_state(TASK_INTERRUPTIBLE);	/* mb paired w/ kthread_stop */
@@ -621,6 +622,98 @@ repeat:
 }
 EXPORT_SYMBOL_GPL(kthread_worker_fn);
 
+static struct kthread_worker *
+__kthread_create_worker(int cpu, const char namefmt[], va_list args)
+{
+	struct kthread_worker *worker;
+	struct task_struct *task;
+
+	worker = kzalloc(sizeof(*worker), GFP_KERNEL);
+	if (!worker)
+		return ERR_PTR(-ENOMEM);
+
+	kthread_init_worker(worker);
+
+	if (cpu >= 0) {
+		char name[TASK_COMM_LEN];
+
+		/*
+		 * kthread_create_worker_on_cpu() allows to pass a generic
+		 * namefmt in compare with kthread_create_on_cpu. We need
+		 * to format it here.
+		 */
+		vsnprintf(name, sizeof(name), namefmt, args);
+		task = kthread_create_on_cpu(kthread_worker_fn, worker,
+					     cpu, name);
+	} else {
+		task = __kthread_create_on_node(kthread_worker_fn, worker,
+						-1, namefmt, args);
+	}
+
+	if (IS_ERR(task))
+		goto fail_task;
+
+	worker->task = task;
+	wake_up_process(task);
+	return worker;
+
+fail_task:
+	kfree(worker);
+	return ERR_CAST(task);
+}
+
+/**
+ * kthread_create_worker - create a kthread worker
+ * @namefmt: printf-style name for the kthread worker (task).
+ *
+ * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
+ * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
+ * when the worker was SIGKILLed.
+ */
+struct kthread_worker *
+kthread_create_worker(const char namefmt[], ...)
+{
+	struct kthread_worker *worker;
+	va_list args;
+
+	va_start(args, namefmt);
+	worker = __kthread_create_worker(-1, namefmt, args);
+	va_end(args);
+
+	return worker;
+}
+EXPORT_SYMBOL(kthread_create_worker);
+
+/**
+ * kthread_create_worker_on_cpu - create a kthread worker and bind it
+ *	it to a given CPU and the associated NUMA node.
+ * @cpu: CPU number
+ * @namefmt: printf-style name for the kthread worker (task).
+ *
+ * Use a valid CPU number if you want to bind the kthread worker
+ * to the given CPU and the associated NUMA node.
+ *
+ * A good practice is to add the cpu number also into the worker name.
+ * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
+ *
+ * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
+ * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
+ * when the worker was SIGKILLed.
+ */
+struct kthread_worker *
+kthread_create_worker_on_cpu(int cpu, const char namefmt[], ...)
+{
+	struct kthread_worker *worker;
+	va_list args;
+
+	va_start(args, namefmt);
+	worker = __kthread_create_worker(cpu, namefmt, args);
+	va_end(args);
+
+	return worker;
+}
+EXPORT_SYMBOL(kthread_create_worker_on_cpu);
+
 /* insert @work before @pos in @worker */
 static void kthread_insert_work(struct kthread_worker *worker,
 			       struct kthread_work *work,