[34-longterm 214/247] USB: uss720 fixup refcount position

From: Paul Gortmaker
Date: Thu Jun 23 2011 - 13:48:14 EST

From: Peter Holik <peter@xxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit adaa3c6342b249548ea830fe8e02aa5b45be8688 upstream.

My testprog do a lot of bitbang - after hours i got following warning and my machine lockups:
WARNING: at /build/buildd/linux-2.6.38/lib/kref.c:34
After debugging uss720 driver i discovered that the completion callback was called before
usb_submit_urb returns. The callback frees the request structure that is krefed on return by

Signed-off-by: Peter Holik <peter@xxxxxxxx>
Acked-by: Thomas Sailer <t.sailer@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
drivers/usb/misc/uss720.c | 7 +++----
1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index 4ff2158..9727daa 100644
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -177,12 +177,11 @@ static struct uss720_async_request *submit_async_request(struct parport_uss720_p
spin_lock_irqsave(&priv->asynclock, flags);
list_add_tail(&rq->asynclist, &priv->asynclist);
spin_unlock_irqrestore(&priv->asynclock, flags);
+ kref_get(&rq->ref_count);
ret = usb_submit_urb(rq->urb, mem_flags);
- if (!ret) {
- kref_get(&rq->ref_count);
+ if (!ret)
return rq;
- }
- kref_put(&rq->ref_count, destroy_async);
+ destroy_async(&rq->ref_count);
err("submit_async_request submit_urb failed with %d", ret);
return NULL;

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