linux-kernel - Re: [PACTH v2] cdc-wdm: Clear read pipeline in case of error

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Message-ID: <1470745099.2195.9.camel@suse.com>
Date:	Tue, 09 Aug 2016 14:18:19 +0200
From:	Oliver Neukum <oneukum@...e.com>
To:	robert.foss@...labora.com
Cc:	Ben Chan <benchan@...omium.org>,
	Prathmesh Prabhu <pprabhu@...omium.org>,
	Guenter Roeck <groeck@...gle.com>, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PACTH v2] cdc-wdm: Clear read pipeline in case of error

On Mon, 2016-08-08 at 11:48 -0400, robert.foss@...labora.com wrote:
> From: Robert Foss <robert.foss@...labora.com>
> 
> Implemented queued response handling. This queue is processed every time the
> WDM_READ flag is cleared.
> 
> In case of a read error, userspace may not actually read the data, since the
> driver returns an error through wdm_poll. After this, the underlying device may
> attempt to send us more data, but the queue is not processed. While userspace is
> also blocked, because the read error is never cleared.
> 
> After this patch, we proactively process the queue on a read error. If there was
> an outstanding response to handle, that will clear the error (or go through the
> same logic again, if another read error occurs). If there was no outstanding
> response, this will bring the queue size back to 0, unblocking a future response
> from the underlying device.
> 
> Tested-by: Robert Foss <robert.foss@...labora.com>
> Signed-off-by: Robert Foss <robert.foss@...labora.com>
Acked-by: Oliver Neukum <oneukum@...e.com>