Re: [PATCH] mtd_blkdevs: Convert to use the kthread API

[Christoph Hellwig <hch@infradead.org>]

On Sun, Apr 22, 2007 at 01:24:53PM +0100, Christoph Hellwig wrote:
> On Thu, Apr 19, 2007 at 12:55:28AM -0600, Eric W. Biederman wrote:
> > From: Eric W. Biederman <ebiederm@xmission.com> - unquoted
> > 
> > thread_run is used intead of kernel_thread, daemonize, and mucking
> > around blocking signals directly.
> 
> This is the full conversion I sent to Dave in April 2006, but never got
> any feedback to:

Here's a slightly updated version that corrects the set_current_state
placement as discussed with Dave on irc:


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: linux-2.6/drivers/mtd/mtd_blkdevs.c
===================================================================
--- linux-2.6.orig/drivers/mtd/mtd_blkdevs.c	2007-01-29 10:03:52.000000000 +0100
+++ linux-2.6/drivers/mtd/mtd_blkdevs.c	2007-04-22 20:39:20.000000000 +0200
@@ -20,6 +20,7 @@
 #include <linux/hdreg.h>
 #include <linux/init.h>
 #include <linux/mutex.h>
+#include <linux/kthread.h>
 #include <asm/uaccess.h>
 
 static LIST_HEAD(blktrans_majors);
@@ -28,9 +29,7 @@ extern struct mutex mtd_table_mutex;
 extern struct mtd_info *mtd_table[];
 
 struct mtd_blkcore_priv {
-	struct completion thread_dead;
-	int exiting;
-	wait_queue_head_t thread_wq;
+	struct task_struct *thread;
 	struct request_queue *rq;
 	spinlock_t queue_lock;
 };
@@ -83,38 +82,19 @@ static int mtd_blktrans_thread(void *arg
 	/* we might get involved when memory gets low, so use PF_MEMALLOC */
 	current->flags |= PF_MEMALLOC | PF_NOFREEZE;
 
-	daemonize("%sd", tr->name);
-
-	/* daemonize() doesn't do this for us since some kernel threads
-	   actually want to deal with signals. We can't just call
-	   exit_sighand() since that'll cause an oops when we finally
-	   do exit. */
-	spin_lock_irq(&current->sighand->siglock);
-	sigfillset(&current->blocked);
-	recalc_sigpending();
-	spin_unlock_irq(&current->sighand->siglock);
-
 	spin_lock_irq(rq->queue_lock);
-
-	while (!tr->blkcore_priv->exiting) {
+	while (!kthread_should_stop()) {
 		struct request *req;
 		struct mtd_blktrans_dev *dev;
 		int res = 0;
-		DECLARE_WAITQUEUE(wait, current);
 
 		req = elv_next_request(rq);
 
 		if (!req) {
-			add_wait_queue(&tr->blkcore_priv->thread_wq, &wait);
 			set_current_state(TASK_INTERRUPTIBLE);
-
 			spin_unlock_irq(rq->queue_lock);
-
 			schedule();
-			remove_wait_queue(&tr->blkcore_priv->thread_wq, &wait);
-
 			spin_lock_irq(rq->queue_lock);
-
 			continue;
 		}
 
@@ -133,13 +113,13 @@ static int mtd_blktrans_thread(void *arg
 	}
 	spin_unlock_irq(rq->queue_lock);
 
-	complete_and_exit(&tr->blkcore_priv->thread_dead, 0);
+	return 0;
 }
 
 static void mtd_blktrans_request(struct request_queue *rq)
 {
 	struct mtd_blktrans_ops *tr = rq->queuedata;
-	wake_up(&tr->blkcore_priv->thread_wq);
+	wake_up_process(tr->blkcore_priv->thread);
 }
 
 
@@ -388,8 +368,6 @@ int register_mtd_blktrans(struct mtd_blk
 		return ret;
 	}
 	spin_lock_init(&tr->blkcore_priv->queue_lock);
-	init_completion(&tr->blkcore_priv->thread_dead);
-	init_waitqueue_head(&tr->blkcore_priv->thread_wq);
 
 	tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
 	if (!tr->blkcore_priv->rq) {
@@ -403,13 +381,14 @@ int register_mtd_blktrans(struct mtd_blk
 	blk_queue_hardsect_size(tr->blkcore_priv->rq, tr->blksize);
 	tr->blkshift = ffs(tr->blksize) - 1;
 
-	ret = kernel_thread(mtd_blktrans_thread, tr, CLONE_KERNEL);
-	if (ret < 0) {
+	tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread, tr,
+			"%sd", tr->name);
+	if (IS_ERR(tr->blkcore_priv->thread)) {
 		blk_cleanup_queue(tr->blkcore_priv->rq);
 		unregister_blkdev(tr->major, tr->name);
 		kfree(tr->blkcore_priv);
 		mutex_unlock(&mtd_table_mutex);
-		return ret;
+		return PTR_ERR(tr->blkcore_priv->thread);
 	}
 
 	INIT_LIST_HEAD(&tr->devs);
@@ -432,9 +411,7 @@ int deregister_mtd_blktrans(struct mtd_b
 	mutex_lock(&mtd_table_mutex);
 
 	/* Clean up the kernel thread */
-	tr->blkcore_priv->exiting = 1;
-	wake_up(&tr->blkcore_priv->thread_wq);
-	wait_for_completion(&tr->blkcore_priv->thread_dead);
+	kthread_stop(tr->blkcore_priv->thread);
 
 	/* Remove it from the list of active majors */
 	list_del(&tr->list);
-
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