linux-kernel - [PATCH] vhost: fix signed/unsigned comparison

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Date:	Mon, 10 Jan 2011 10:03:21 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org,
	virtualization@...ts.osdl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jes.Sorensen@...hat.com,
	stable@...nel.org
Subject: [PATCH] vhost: fix signed/unsigned comparison

To detect that a sequence number is done, we are doing math on unsigned
integers so the result is unsigned too. Not what was intended for the <=
comparison. The result is user stuck forever in flush call.
Convert to int to fix this.

Further, get rid of ({}) to make code clearer.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---

I've put this on my vhost.git tree.

 drivers/vhost/vhost.c |   18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 159c77a..522b8fc 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -98,22 +98,26 @@ void vhost_poll_stop(struct vhost_poll *poll)
 	remove_wait_queue(poll->wqh, &poll->wait);
 }
 
+static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
+				unsigned seq)
+{
+	int left;
+	spin_lock_irq(&dev->work_lock);
+	left = seq - work->done_seq;
+	spin_unlock_irq(&dev->work_lock);
+	return left <= 0;
+}
+
 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
 {
 	unsigned seq;
-	int left;
 	int flushing;
 
 	spin_lock_irq(&dev->work_lock);
 	seq = work->queue_seq;
 	work->flushing++;
 	spin_unlock_irq(&dev->work_lock);
-	wait_event(work->done, ({
-		   spin_lock_irq(&dev->work_lock);
-		   left = seq - work->done_seq <= 0;
-		   spin_unlock_irq(&dev->work_lock);
-		   left;
-	}));
+	wait_event(work->done, vhost_work_seq_done(dev, work, seq));
 	spin_lock_irq(&dev->work_lock);
 	flushing = --work->flushing;
 	spin_unlock_irq(&dev->work_lock);
-- 
1.7.3.2.91.g446ac
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