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SubjectRe: [Outreachy kernel] [PATCH v2] staging: iio: ade7753: replace mlock with driver private lock
On Thu, Mar 16, 2017 at 3:23 AM, Jonathan Cameron <jic23@kernel.org> wrote:
> 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@gmail.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.

Jonathon, what I found by looking at the codes of other drivers is that
we have to use mutex_init in probe function only.

Is this correct?

And this patch also suggest the same:-
https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=testing&id=388c8f18ff29fe95dbf72cb0a1bd8fbcd6f52f8f

>>
>>
>>>
>>> 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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