From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752979AbaIXKMP (ORCPT ); Wed, 24 Sep 2014 06:12:15 -0400 Received: from mail-ig0-f177.google.com ([209.85.213.177]:42440 "EHLO mail-ig0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750940AbaIXKMN (ORCPT ); Wed, 24 Sep 2014 06:12:13 -0400 Date: Wed, 24 Sep 2014 11:12:06 +0100 From: Lee Jones To: Octavian Purdila Cc: linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, johan@kernel.org, Octavian Purdila Subject: Re: [PATCH v2 1/2] mfd: viperboard: allocate I/O buffer separately Message-ID: <20140924101206.GD19999@lee--X1> References: <1411414759-7056-1-git-send-email-octavian.purdila@intel.com> <1411414759-7056-2-git-send-email-octavian.purdila@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1411414759-7056-2-git-send-email-octavian.purdila@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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_*)? > + if (vb->buf == NULL) { > + ret = -ENOMEM; > + goto error; > + } > + > mutex_init(&vb->lock); > > vb->usb_dev = usb_get_dev(interface_to_usbdev(interface)); > @@ -105,6 +111,7 @@ static int vprbrd_probe(struct usb_interface *interface, > error: > if (vb) { > usb_put_dev(vb->usb_dev); > + kfree(vb->buf); Then you don't need this. > kfree(vb); > } > > @@ -118,6 +125,7 @@ static void vprbrd_disconnect(struct usb_interface *interface) > mfd_remove_devices(&interface->dev); > usb_set_intfdata(interface, NULL); > usb_put_dev(vb->usb_dev); > + kfree(vb->buf); Or this. > kfree(vb); > > dev_dbg(&interface->dev, "disconnected\n"); > diff --git a/include/linux/mfd/viperboard.h b/include/linux/mfd/viperboard.h > index 1934528..af928d0 100644 > --- a/include/linux/mfd/viperboard.h > +++ b/include/linux/mfd/viperboard.h > @@ -103,7 +103,7 @@ struct vprbrd_i2c_addr_msg { > struct vprbrd { > struct usb_device *usb_dev; /* the usb device for this device */ > struct mutex lock; > - u8 buf[sizeof(struct vprbrd_i2c_write_msg)]; > + u8 *buf; > struct platform_device pdev; > }; > -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog