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

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Date:   Wed, 26 Jun 2019 11:06:45 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Neil Armstrong <narmstrong@...libre.com>, 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

Quoting Neil Armstrong (2019-06-26 01:24:47)
> 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.

s/mesure/measure/

> >>
> >> 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...
> 

Sounds plausible to me.