Re: [Outreachy kernel] [PATCH v6] staging: Use buf_lock instead of mlock and Refactor code

[SIMRAN SINGHAL]

On Tue, Mar 21, 2017 at 10:18 PM, Alison Schofield <amsfield22@xxxxxxxxx> wrote:
> On Mon, Mar 20, 2017 at 01:36:21AM +0530, simran singhal wrote:
>
> Hi Simran,
>
> I going to ask for a v7 without looking at the code ;)
> Subject line needs subsystem and driver.
> Subject and log message can be improved.
>
>> 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 buf_lock in the devices global data.
>            ^^^^^^^^^^^ this was not done
>>
>> As buf_lock protects both the adis16060_spi_write() and
>> adis16060_spi_read() functions and both are always called in
>> pair. First write, then read. Thus, refactor the code to have
>> one single function adis16060_spi_write_than_read() which is
>> protected by the existing buf_lock.
> This was done.  So, you were able to obsolete the need for mlock
> by creating the paired function.

I am still using mlock but now locking it and performing both write and
read and than unlocking.

So, now have a single safe function.

>
>>
>> Removed nested locks as the function adis16060_read_raw call
>> a lock on &st->buf_lock and then calls the function
>> adis16060_spi_write which again tries to get hold
>> of the same lock.
> ^^^^ this was not done.  Yes, you avoided nested locks through
> proper coding, but we don't want to give the impression in the
> log message that there was a pre-existing nested lock issue.
>
> I did checkpatch & compile it...but looked no further yet.
>
> alisons
>>
>> Signed-off-by: simran singhal <singhalsimran0@xxxxxxxxx>
>> ---
>>
>>  v6:
>>    -Change commit message
>>    -Remove nested lock
>>
>>  drivers/staging/iio/gyro/adis16060_core.c | 40 ++++++++++---------------------
>>  1 file changed, 13 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/staging/iio/gyro/adis16060_core.c b/drivers/staging/iio/gyro/adis16060_core.c
>> index c9d46e7..1c6de46 100644
>> --- a/drivers/staging/iio/gyro/adis16060_core.c
>> +++ b/drivers/staging/iio/gyro/adis16060_core.c
>> @@ -40,25 +40,17 @@ struct adis16060_state {
>>
>>  static struct iio_dev *adis16060_iio_dev;
>>
>> -static int adis16060_spi_write(struct iio_dev *indio_dev, u8 val)
>> +static int adis16060_spi_write_than_read(struct iio_dev *indio_dev,
>> +                                      u8 conf, u16 *val)
>>  {
>>       int ret;
>>       struct adis16060_state *st = iio_priv(indio_dev);
>>
>> -     mutex_lock(&st->buf_lock);
>> -     st->buf[2] = val; /* The last 8 bits clocked in are latched */
>> +     st->buf[2] = conf; /* The last 8 bits clocked in are latched */
>>       ret = spi_write(st->us_w, st->buf, 3);
>> -     mutex_unlock(&st->buf_lock);
>> -
>> -     return ret;
>> -}
>> -
>> -static int adis16060_spi_read(struct iio_dev *indio_dev, u16 *val)
>> -{
>> -     int ret;
>> -     struct adis16060_state *st = iio_priv(indio_dev);
>>
>> -     mutex_lock(&st->buf_lock);
>> +     if (ret < 0)
>> +             return ret;
>>
>>       ret = spi_read(st->us_r, st->buf, 3);
>>
>> @@ -69,8 +61,8 @@ static int adis16060_spi_read(struct iio_dev *indio_dev, u16 *val)
>>        */
>>       if (!ret)
>>               *val = ((st->buf[0] & 0x3) << 12) |
>> -                     (st->buf[1] << 4) |
>> -                     ((st->buf[2] >> 4) & 0xF);
>> +                      (st->buf[1] << 4) |
>> +                      ((st->buf[2] >> 4) & 0xF);
>>       mutex_unlock(&st->buf_lock);
>>
>>       return ret;
>> @@ -83,20 +75,18 @@ static int adis16060_read_raw(struct iio_dev *indio_dev,
>>  {
>>       u16 tval = 0;
>>       int ret;
>> +     struct adis16060_state *st = iio_priv(indio_dev);
>>
>>       switch (mask) {
>>       case IIO_CHAN_INFO_RAW:
>>               /* Take the iio_dev status lock */
>> -             mutex_lock(&indio_dev->mlock);
>> -             ret = adis16060_spi_write(indio_dev, chan->address);
>> +             mutex_lock(&st->buf_lock);
>> +             ret = adis16060_spi_write_than_read(indio_dev,
>> +                                                 chan->address, &tval);
>> +             mutex_unlock(&st->buf_lock);
>>               if (ret < 0)
>> -                     goto out_unlock;
>> +                     return ret;
>>
>> -             ret = adis16060_spi_read(indio_dev, &tval);
>> -             if (ret < 0)
>> -                     goto out_unlock;
>> -
>> -             mutex_unlock(&indio_dev->mlock);
>>               *val = tval;
>>               return IIO_VAL_INT;
>>       case IIO_CHAN_INFO_OFFSET:
>> @@ -110,10 +100,6 @@ static int adis16060_read_raw(struct iio_dev *indio_dev,
>>       }
>>
>>       return -EINVAL;
>> -
>> -out_unlock:
>> -     mutex_unlock(&indio_dev->mlock);
>> -     return ret;
>>  }
>>
>>  static const struct iio_info adis16060_info = {
>> --
>> 2.7.4
>>
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