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SubjectRe: [Outreachy kernel] [PATCH v2] staging: iio: ade7753: replace mlock with driver private lock
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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.
>
> 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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