RE: [PATCH v3 1/1] usb: cdc-acm: handle unlinked urb in acm read callback

From: Tang, Jianqiang
Date: Wed Jan 20 2016 - 02:09:10 EST

Hi Greg,

Sorry to disturb you although I know you are very busy :)
One question is about this patch, does the patch already in the process of merge into kernel?
Or need modify still?

Thanks a lot!

-----Original Message-----
From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of Lu Baolu
Sent: Wednesday, December 30, 2015 12:59 PM
To: Oliver Neukum <oliver@xxxxxxxxxx>; Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: linux-usb@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Lu Baolu <>; Tang, Jianqiang <jianqiang.tang@xxxxxxxxx>; stable@xxxxxxxxxxxxxxx
Subject: [PATCH v3 1/1] usb: cdc-acm: handle unlinked urb in acm read callback

In current acm driver, the bulk-in callback function ignores the URBs unlinked in usb core.

This causes unexpected data loss in some cases. For example, runtime suspend entry will unlinked all urbs and set urb->status to -ENOENT even those urbs might have data not processed yet.
Hence, data loss occurs.

This patch lets bulk-in callback function handle unlinked urbs to avoid data loss.

Signed-off-by: Tang Jian Qiang <jianqiang.tang@xxxxxxxxx>
Signed-off-by: Lu Baolu <>
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Oliver Neukum <oneukum@xxxxxxxx>
drivers/usb/class/cdc-acm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

change log:
add Acked-by: Oliver Neukum <oneukum@xxxxxxxx>.

add the change log.

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 26ca4f9..8cd193b 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -428,7 +428,8 @@ static void acm_read_bulk_callback(struct urb *urb)
set_bit(rb->index, &acm->read_urbs_free);
dev_dbg(&acm->data->dev, "%s - non-zero urb status: %d\n",
__func__, status);
- return;
+ if ((status != -ENOENT) || (urb->actual_length == 0))
+ return;


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