From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754012AbaIXM3f (ORCPT ); Wed, 24 Sep 2014 08:29:35 -0400 Received: from mail-la0-f41.google.com ([209.85.215.41]:64599 "EHLO mail-la0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751201AbaIXM3c (ORCPT ); Wed, 24 Sep 2014 08:29:32 -0400 X-Google-Original-Sender: Date: Wed, 24 Sep 2014 14:26:58 +0200 From: Johan Hovold To: Lee Jones Cc: Johan Hovold , Octavian Purdila , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: [PATCH v2 1/2] mfd: viperboard: allocate I/O buffer separately Message-ID: <20140924122658.GD17019@localhost> References: <1411414759-7056-1-git-send-email-octavian.purdila@intel.com> <1411414759-7056-2-git-send-email-octavian.purdila@intel.com> <20140924101206.GD19999@lee--X1> <20140924102853.GA17019@localhost> <20140924120002.GA32069@lee--X1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140924120002.GA32069@lee--X1> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 24, 2014 at 01:00:02PM +0100, Lee Jones wrote: > On Wed, 24 Sep 2014, Johan Hovold wrote: > > > On Wed, Sep 24, 2014 at 11:12:06AM +0100, Lee Jones wrote: > > > On Mon, 22 Sep 2014, Octavian Purdila wrote: > > > > > > > Currently the I/O buffer is allocated part of the device status > > > > structure, potentially sharing the same cache line with other members > > > > in this structure. > > > > > > > > Allocate the buffer separately, to avoid the I/O operations corrupting > > > > the device status structure due to cache line sharing. > > > > > > > > Compiled tested only as I don't have access to hardware. > > > > > > > > Signed-off-by: Octavian Purdila > > > > --- > > > > drivers/mfd/viperboard.c | 8 ++++++++ > > > > include/linux/mfd/viperboard.h | 2 +- > > > > 2 files changed, 9 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c > > > > index e00f534..5f62f4e 100644 > > > > --- a/drivers/mfd/viperboard.c > > > > +++ b/drivers/mfd/viperboard.c > > > > @@ -64,6 +64,12 @@ static int vprbrd_probe(struct usb_interface *interface, > > > > return -ENOMEM; > > > > } > > > > > > > > + vb->buf = kzalloc(sizeof(struct vprbrd_i2c_write_msg), GFP_KERNEL); > > > > > > Can you obtain the 'struct device' first then use managed resources > > > (devm_*)? > > > > I think any devres conversion should be done in a follow-up patch and > > not be included in the fix (e.g. in order to facilitate backporting). We > > also don't want to mix allocation schemes. > > I agree, but equally I'm not keen on accepting this patch as I believe > it could be done better. > > Please submit two patches, one converting to shared resources and this > being the subsequent one, fixed up to do the right thing. A buffer-corruption fix is a candidate for stable, whereas a devres conversion (clean up) is not. Hence the former should not depend on the latter. Johan