[patch] fix keventd execution dependency

[Ingo Molnar <mingo@elte.hu>]

[-- Attachment #1: Type: text/plain, Size: 255 bytes --]


We dont want to execute off keventd since it might hold a semaphore our
callers hold too. This can happen when kthread_create() is called from
within keventd. This happened due to the IRQ threading patches but it
could happen with other code too.

	Ingo

[-- Attachment #2: fix-keventd.patch --]
[-- Type: text/plain, Size: 1425 bytes --]


We dont want to execute off keventd since it might hold a semaphore our
callers hold too. This can happen when kthread_create() is called from
within keventd. This happened due to the IRQ threading patches but it
could happen with other code too.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

--- linux/kernel/kthread.c.orig	
+++ linux/kernel/kthread.c	
@@ -14,6 +14,12 @@
 #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. */
@@ -126,12 +132,13 @@ struct task_struct *kthread_create(int (
 	init_completion(&create.started);
 	init_completion(&create.done);
 
-	/* If we're being called to start the first workqueue, we
-	 * can't use keventd. */
-	if (!keventd_up())
+	/*
+	 * The workqueue needs to start up first:
+	 */
+	if (!helper_wq)
 		work.func(work.data);
 	else {
-		schedule_work(&work);
+		queue_work(helper_wq, &work);
 		wait_for_completion(&create.done);
 	}
 	if (!IS_ERR(create.result)) {
@@ -183,3 +190,13 @@ int kthread_stop(struct task_struct *k)
 	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);
+