Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752689AbdCMOB6 (ORCPT ); Mon, 13 Mar 2017 10:01:58 -0400 Received: from www381.your-server.de ([78.46.137.84]:48893 "EHLO www381.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751119AbdCMOBx (ORCPT ); Mon, 13 Mar 2017 10:01:53 -0400 Subject: Re: [PATCH] staging: iio: ade7753: replace mlock with driver private lock To: SIMRAN SINGHAL References: <20170312133250.GA7772@singhal-Inspiron-5558> <6e55c61d-7587-4191-1fc5-de43e26986d7@metafoo.de> Cc: Michael Hennerich , Jonathan Cameron , Hartmut Knaack , Pete Meerwald-Stadler , Greg Kroah-Hartman , linux-iio@vger.kernel.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, outreachy-kernel From: Lars-Peter Clausen Message-ID: <221527ad-aad4-5bfc-29da-d56880357c11@metafoo.de> Date: Mon, 13 Mar 2017 14:34:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Authenticated-Sender: lars@metafoo.de Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3069 Lines: 80 On 03/13/2017 01:33 PM, SIMRAN SINGHAL wrote: > On Mon, Mar 13, 2017 at 5:30 PM, Lars-Peter Clausen wrote: >> On 03/12/2017 02:32 PM, simran singhal wrote: >>> The IIO subsystem is redefining iio_dev->mlock to be used by >>> the IIO core only for protecting device operating mode changes. >>> ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes. >>> >>> In this driver, mlock was being used to protect hardware state >>> changes. Replace it with a lock in the devices global data. >>> >>> Fix some coding style issues related to white space also. >>> >>> Signed-off-by: simran singhal >>> --- >>> drivers/staging/iio/meter/ade7753.c | 14 ++++++++------ >>> 1 file changed, 8 insertions(+), 6 deletions(-) >>> >>> diff --git a/drivers/staging/iio/meter/ade7753.c b/drivers/staging/iio/meter/ade7753.c >>> index dfd8b71..ca99d82 100644 >>> --- a/drivers/staging/iio/meter/ade7753.c >>> +++ b/drivers/staging/iio/meter/ade7753.c >>> @@ -81,12 +81,14 @@ >>> * @tx: transmit buffer >>> * @rx: receive buffer >>> * @buf_lock: mutex to protect tx and rx >>> + * @lock: protect sensor state >> >> It might make sense to reuse the existing lock which currently protects the >> read/write functions. You can do this by introducing a variant of >> ade7753_spi_{read,write}_reg_16() that does not take a lock and use these to >> implement the read-modify-write cycle in a protected section. >> >> Looking through the driver there seem to be other places as well that do >> read-modify-write that should be protected by a lock, but currently are not. >> This might be a good task. >> > > Are you trying to say that their is no need of introducing "lock", > I can using "buf_lock" only. Yes, there should be no need for two locks. But you need to slightly refactor the code to avoid taking the same lock nested. > > Thanks! > >>> **/ >>> struct ade7753_state { >>> - struct spi_device *us; >>> - struct mutex buf_lock; >>> - u8 tx[ADE7753_MAX_TX] ____cacheline_aligned; >>> - u8 rx[ADE7753_MAX_RX]; >>> + struct spi_device *us; >>> + struct mutex buf_lock; >>> + struct mutex lock; /* protect sensor state */ >>> + u8 tx[ADE7753_MAX_TX] ____cacheline_aligned; >>> + u8 rx[ADE7753_MAX_RX]; >>> }; >>> >>> static int ade7753_spi_write_reg_8(struct device *dev, >>> @@ -484,7 +486,7 @@ static ssize_t ade7753_write_frequency(struct device *dev, >>> if (!val) >>> return -EINVAL; >>> >>> - mutex_lock(&indio_dev->mlock); >>> + mutex_lock(&st->lock); >>> >>> t = 27900 / val; >>> if (t > 0) >>> @@ -505,7 +507,7 @@ static ssize_t ade7753_write_frequency(struct device *dev, >>> ret = ade7753_spi_write_reg_16(dev, ADE7753_MODE, reg); >>> >>> out: >>> - mutex_unlock(&indio_dev->mlock); >>> + mutex_unlock(&st->lock); >>> >>> return ret ? ret : len; >>> } >>> >>