linux-kernel - Re: [RFC/RFT 05/14] soc: amlogic: meson-clk-measure: protect measure with a mutex

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Message-ID: <2ceca0ca-8f8e-78a8-df39-67a763f28f30@baylibre.com>
Date:   Wed, 26 Jun 2019 10:24:47 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Stephen Boyd <sboyd@...nel.org>, jbrunet@...libre.com,
        khilman@...libre.com
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, martin.blumenstingl@...glemail.com
Subject: Re: [RFC/RFT 05/14] soc: amlogic: meson-clk-measure: protect measure
 with a mutex

On 25/06/2019 22:27, Stephen Boyd wrote:
> Quoting Neil Armstrong (2019-06-20 08:00:04)
>> In order to protect clock measuring when multiple process asks for
>> a mesure, protect the main measure function with mutexes.
>>
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> ---
>>  drivers/soc/amlogic/meson-clk-measure.c | 12 +++++++++++-
>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/soc/amlogic/meson-clk-measure.c b/drivers/soc/amlogic/meson-clk-measure.c
>> index 19d4cbc93a17..c470e24f1dfa 100644
>> --- a/drivers/soc/amlogic/meson-clk-measure.c
>> +++ b/drivers/soc/amlogic/meson-clk-measure.c
>> @@ -11,6 +11,8 @@
>>  #include <linux/debugfs.h>
>>  #include <linux/regmap.h>
>>  
>> +static DEFINE_MUTEX(measure_lock);
>> +
>>  #define MSR_CLK_DUTY           0x0
>>  #define MSR_CLK_REG0           0x4
>>  #define MSR_CLK_REG1           0x8
>> @@ -360,6 +362,10 @@ static int meson_measure_id(struct meson_msr_id *clk_msr_id,
>>         unsigned int val;
>>         int ret;
>>  
>> +       ret = mutex_lock_interruptible(&measure_lock);
> 
> Why interruptible?


I supposed _interruptible was needed since it's called from userspace via
debugfs, locking indefinitely isn't wanted, no ? or maybe I missed something...

Neil

> 
>> +       if (ret)
>> +               return ret;
>> +
>>         regmap_write(priv->regmap, MSR_CLK_REG0, 0);
>>  
>>         /* Set measurement duration */