From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935603AbcLTTAM (ORCPT ); Tue, 20 Dec 2016 14:00:12 -0500 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:50458 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933853AbcLTS7H (ORCPT ); Tue, 20 Dec 2016 13:59:07 -0500 X-ME-Sender: X-Sasl-enc: o3iCp0sgle3XEm/TkSU/UpLyBZKq3KeP6/LZW1xVkGPT 1482260346 Date: Tue, 20 Dec 2016 11:59:05 -0700 From: Mark Greer To: Geoff Lansberry Cc: linux-wireless@vger.kernel.org, lauro.venancio@openbossa.org, aloisio.almeida@openbossa.org, sameo@linux.intel.com, robh+dt@kernel.org, mark.rutland@arm.com, netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, justin@kuvee.com, Jaret Cantu Subject: Re: [PATCH 3/3] nfc: trf7970a: Prevent repeated polling from crashing the kernel Message-ID: <20161220185905.GA5867@animalcreek.com> References: <1482250592-4268-1-git-send-email-glansberry@gmail.com> <1482250592-4268-3-git-send-email-glansberry@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1482250592-4268-3-git-send-email-glansberry@gmail.com> Organization: Animal Creek Technologies, Inc. User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 20, 2016 at 11:16:32AM -0500, Geoff Lansberry wrote: > From: Jaret Cantu > > Repeated polling attempts cause a NULL dereference error to occur. > This is because the state of the trf7970a is currently reading but > another request has been made to send a command before it has finished. How is this happening? Was trf7970a_abort_cmd() called and it didn't work right? Was it not called at all and there is a bug in the digital layer? More details please. > The solution is to properly kill the waiting reading (workqueue) > before failing on the send. If the bug is in the calling code, then that is what should get fixed. This seems to be a hack to work-around a digital layer bug. Mark --