Re: [PATCH v3 4/4] drivers/thermal/exymos: Use guard notation when acquiring mutex

Lukasz Luba <lukasz.luba@xxxxxxx> · Thu, 6 Mar 2025 09:15:30 +0000

On 3/5/25 15:59, Anand Moon wrote:
Hi Lukasz,

On Wed, 5 Mar 2025 at 14:12, Lukasz Luba <lukasz.luba@xxxxxxx> wrote:



On 3/4/25 12:20, Anand Moon wrote:
Hi Lukasz,

On Sat, 1 Mar 2025 at 00:06, Anand Moon <linux.amoon@xxxxxxxxx> wrote:

Hi Lukasz,

On Fri, 28 Feb 2025 at 22:58, Lukasz Luba <lukasz.luba@xxxxxxx> wrote:



On 2/16/25 19:58, Anand Moon wrote:
Using guard notation makes the code more compact and error handling
more robust by ensuring that mutexes are released in all code paths
when control leaves critical section.

Signed-off-by: Anand Moon <linux.amoon@xxxxxxxxx>
---
v3: new patch
---
    drivers/thermal/samsung/exynos_tmu.c | 21 +++++++--------------
    1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
index fe090c1a93ab..a34ba3858d64 100644
--- a/drivers/thermal/samsung/exynos_tmu.c
+++ b/drivers/thermal/samsung/exynos_tmu.c
@@ -256,7 +256,7 @@ static int exynos_tmu_initialize(struct platform_device *pdev)
        unsigned int status;
        int ret = 0;

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);
        clk_enable(data->clk_sec);

@@ -270,7 +270,6 @@ static int exynos_tmu_initialize(struct platform_device *pdev)

        clk_disable(data->clk_sec);
        clk_disable(data->clk);
-     mutex_unlock(&data->lock);

        return ret;
    }
@@ -292,13 +291,12 @@ static int exynos_thermal_zone_configure(struct platform_device *pdev)
                return ret;
        }

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);

        data->tmu_set_crit_temp(data, temp / MCELSIUS);

        clk_disable(data->clk);
-     mutex_unlock(&data->lock);

        return 0;
    }
@@ -325,12 +323,11 @@ static void exynos_tmu_control(struct platform_device *pdev, bool on)
    {
        struct exynos_tmu_data *data = platform_get_drvdata(pdev);

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);
        data->tmu_control(pdev, on);
        data->enabled = on;
        clk_disable(data->clk);
-     mutex_unlock(&data->lock);
    }

    static void exynos_tmu_update_bit(struct exynos_tmu_data *data, int reg_off,
@@ -645,7 +642,7 @@ static int exynos_get_temp(struct thermal_zone_device *tz, int *temp)
                 */
                return -EAGAIN;

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);

        value = data->tmu_read(data);
@@ -655,7 +652,6 @@ static int exynos_get_temp(struct thermal_zone_device *tz, int *temp)
                *temp = code_to_temp(data, value) * MCELSIUS;

        clk_disable(data->clk);
-     mutex_unlock(&data->lock);

        return ret;
    }
@@ -720,11 +716,10 @@ static int exynos_tmu_set_emulation(struct thermal_zone_device *tz, int temp)
        if (temp && temp < MCELSIUS)
                goto out;

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);
        data->tmu_set_emulation(data, temp);
        clk_disable(data->clk);
-     mutex_unlock(&data->lock);
        return 0;
    out:
        return ret;
@@ -760,14 +755,13 @@ static irqreturn_t exynos_tmu_threaded_irq(int irq, void *id)

        thermal_zone_device_update(data->tzd, THERMAL_EVENT_UNSPECIFIED);

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);

        /* TODO: take action based on particular interrupt */
        data->tmu_clear_irqs(data);

        clk_disable(data->clk);
-     mutex_unlock(&data->lock);

        return IRQ_HANDLED;
    }
@@ -987,7 +981,7 @@ static int exynos_set_trips(struct thermal_zone_device *tz, int low, int high)
    {
        struct exynos_tmu_data *data = thermal_zone_device_priv(tz);

-     mutex_lock(&data->lock);
+     guard(mutex)(&data->lock);
        clk_enable(data->clk);

        if (low > INT_MIN)
@@ -1000,7 +994,6 @@ static int exynos_set_trips(struct thermal_zone_device *tz, int low, int high)
                data->tmu_disable_high(data);

        clk_disable(data->clk);
-     mutex_unlock(&data->lock);

        return 0;
    }

Thanks for your review comments.

IMO you should be able to even use something like we have
core framework:

guard(thermal_zone)(tz);

Your mutex name is simply 'lock' in the struct exynos_tmu_data
so you should be able to leverage this by:

guard(exynos_tmu_data)(data);


If I introduce the guard it creates a compilation error

amoon@anand-m920q:~/mainline/linux-exynos-6.y-devel$ vi
drivers/thermal/samsung/exynos_tmu.c +306
amoon@anand-m920q:~/mainline/linux-exynos-6.y-devel$ make -j$(nproc)
ARCH=arm CROSS_COMPILE=arm-none-eabi- LOCALVERSION=-u3ml dtbs zImage
modules
    CALL    scripts/checksyscalls.sh
    CHK     kernel/kheaders_data.tar.xz
    CC      drivers/thermal/samsung/exynos_tmu.o
    CC [M]  drivers/md/raid10.o
In file included from ./include/linux/irqflags.h:17,
                   from ./arch/arm/include/asm/bitops.h:28,
                   from ./include/linux/bitops.h:68,
                   from ./include/linux/kernel.h:23,
                   from ./include/linux/clk.h:13,
                   from drivers/thermal/samsung/exynos_tmu.c:14:
drivers/thermal/samsung/exynos_tmu.c: In function 'exynos_tmu_update_bit':
./include/linux/cleanup.h:258:9: error: unknown type name
'class_exynos_tmu_data_t'
    258 |         class_##_name##_t var
__cleanup(class_##_name##_destructor) =   \
        |         ^~~~~~
./include/linux/cleanup.h:309:9: note: in expansion of macro 'CLASS'
    309 |         CLASS(_name, __UNIQUE_ID(guard))
        |         ^~~~~
drivers/thermal/samsung/exynos_tmu.c:338:9: note: in expansion of macro 'guard'
    338 |         guard(exynos_tmu_data)(data);
        |         ^~~~~
drivers/thermal/samsung/exynos_tmu.c:338:9: error: cleanup argument
not a function

[snip]

Right, you're missing the definition at the begging, like:

DEFINE_GUARD(exynos_tmu_data, struct exynos_tmu_data *,
mutex_lock(&_T->lock),
               mutex_unlock(&_T->lock))

below the struct exynos_tmu_data definition.

Also, make sure you include the cleanup.h (it might not complain,
but it would be explicit and more clear)

Thanks for this tip.
However, incorporating guard(exynos_tmu_data)(data); results
in a recursive deadlock with the mutex during initialization, as this
data structure is common to all the code configurations of Exynos TMU


Fair enough, it would be just a cosmetic change, so do fight with it
too much.

Please continue in v4 with your former approach with the 'guard'.







