linux-kernel - Re: [Outreachy kernel] [PATCH v2] staging: iio: ade7753: replace mlock with driver private lock

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Message-ID: <b9b1e228-f025-bf8d-d367-2939a18bf992@kernel.org>
Date:   Wed, 15 Mar 2017 21:53:30 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alison Schofield <amsfield22@...il.com>,
        simran singhal <singhalsimran0@...il.com>
Cc:     lars@...afoo.de, Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Pete Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, outreachy-kernel@...glegroups.com
Subject: Re: [Outreachy kernel] [PATCH v2] staging: iio: ade7753: replace
 mlock with driver private lock

On 13/03/17 19:53, Alison Schofield wrote:
> On Mon, Mar 13, 2017 at 10:01:07PM +0530, 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 <singhalsimran0@...il.com>
>> ---
>>
>>  v2:
>>    -Removed new lock to reuse the existing lock
> Simran,
> 
> The good news is that you have 2 patches that have similar
> challenges!  I'll suggest picking one, drive it to completion,
> then do the other.
> 
> This has the nested locking issue that Lars warned about.
> Need to refactor to avoid.  Check back on his review comments.
> 
> I suggest dropping those whitespace changes - they appear
> out of place in this patch since you are no longer actually
> touching those lines of code.
> 
> alisons
Also missing a mutex_init, though that may well become irrelevant
with refactoring as suggested.
> 
> 
>>
>>  drivers/staging/iio/meter/ade7753.c | 12 ++++++------
>>  1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/staging/iio/meter/ade7753.c b/drivers/staging/iio/meter/ade7753.c
>> index dfd8b71..d88eaa3 100644
>> --- a/drivers/staging/iio/meter/ade7753.c
>> +++ b/drivers/staging/iio/meter/ade7753.c
>> @@ -83,10 +83,10 @@
>>   * @buf_lock:       mutex to protect tx and rx
>>   **/
>>  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;
>> +	u8          tx[ADE7753_MAX_TX] ____cacheline_aligned;
>> +	u8          rx[ADE7753_MAX_RX];
>>  };
>>  
>>  static int ade7753_spi_write_reg_8(struct device *dev,
>> @@ -484,7 +484,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
>>  	if (!val)
>>  		return -EINVAL;
>>  
>> -	mutex_lock(&indio_dev->mlock);
>> +	mutex_lock(&st->buf_lock);
>>  
>>  	t = 27900 / val;
>>  	if (t > 0)
>> @@ -505,7 +505,7 @@ 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->buf_lock);
>>  
>>  	return ret ? ret : len;
>>  }
>> -- 
>> 2.7.4
>>
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