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SubjectRe: [PATCH 4/4] PM / devfreq: Handle monitor start/stop in the devfreq core
Hi Lukasz,

On Thu, Feb 14, 2019 at 07:01:36PM +0100, Lukasz Luba wrote:
> Hi Matthias,
>
> I have compiled and run your changes on Odroid xu3 and v5.0-rc6.
> There are kernel warnings because of mutex not held in function
> devfreq_monitor_[start|stop]() in use cases:
> 1) a few times during registration of new devices devfreq_add_device()
> 2) poking the device from sysfs

Thanks testing!

I messed up carrying over changes from my v4.19 device kernel
to the tree used for upstreaming :(

Do you still see warnings with the below patch?

Thanks

Matthias

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index a42c37543c190..866fe711b43ca 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -440,7 +440,6 @@ static void devfreq_monitor_stop(struct devfreq *devfreq)

mutex_lock(&devfreq->lock);
devfreq->monitor_state = DEVFREQ_MONITOR_STOPPED;
- mutex_unlock(&devfreq->lock);
}

/**
@@ -596,7 +595,9 @@ static int governor_start(struct devfreq *devfreq)
return err;
}

+ mutex_lock(&devfreq->lock);
devfreq_monitor_start(devfreq);
+ mutex_unlock(&devfreq->lock);

return 0;
}
@@ -614,7 +615,9 @@ static int governor_stop(struct devfreq *devfreq)
"mutex must *not* be held by the caller\n"))
return -EINVAL;

+ mutex_lock(&devfreq->lock);
devfreq_monitor_stop(devfreq);
+ mutex_unlock(&devfreq->lock);

err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP, NULL);
if (err) {
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