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SubjectRe: [Outreachy kernel] [PATCH v2] staging: iio: ade7753: replace mlock with driver private lock
On Sat, Mar 18, 2017 at 11:51 PM, Jonathan Cameron <jic23@kernel.org> wrote:
> On 18/03/17 17:34, SIMRAN SINGHAL wrote:
>> 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?
> Yes, it only needs initializing once.
>>
So, no need of using mutex_init here as the function is not a
probe function.

Thanks
Simran

>> 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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>>>
>

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