Re: [PATCH v2] PM / devfreq: Restart previous governor if new governor fails to start

[Saravana Kannan]

On 10/26/2016 12:22 AM, Chanwoo Choi wrote:
> Hi,
>
> On 2016ë 10ì 26ì 10:25, Saravana Kannan wrote:
> > If the new governor fails to start, switch back to old governor so that the
> > devfreq state is not left in some weird limbo.
> >
> > Signed-off-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
> > ---
> > * Fixed typo in commit text
> > * Fixed potential NULL deref
> >
> >   drivers/devfreq/devfreq.c | 9 +++++++--
> >   1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > index bf3ea76..243253e 100644
> > --- a/drivers/devfreq/devfreq.c
> > +++ b/drivers/devfreq/devfreq.c
> > @@ -919,7 +919,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
> >   	struct devfreq *df = to_devfreq(dev);
> >   	int ret;
> >   	char str_governor[DEVFREQ_NAME_LEN + 1];
> > -	struct devfreq_governor *governor;
> > +	const struct devfreq_governor *governor, *prev_gov;
> >
> >   	ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor);
> >   	if (ret != 1)
> > @@ -944,12 +944,17 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
> >   			goto out;
> >   		}
> >   	}
> > +	prev_gov = df->governor;
> >   	df->governor = governor;
> >   	strncpy(df->governor_name, governor->name, DEVFREQ_NAME_LEN);
> >   	ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
> > -	if (ret)
> > +	if (ret) {
> >   		dev_warn(dev, "%s: Governor %s not started(%d)\n",
> >   			 __func__, df->governor->name, ret);
> > +		df->governor = prev_gov;
> > +		strncpy(df->governor_name, prev_gov->name, DEVFREQ_NAME_LEN);
> > +		df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
> > +	}

Sigh... looks like I added the changes to the index but forgot to commit 
it before I sent the patch. Will send v3.

> >   out:
> >   	mutex_unlock(&devfreq_list_lock);
>
> Looks good to me.
> But, how about using the 'prev_governor' instead of 'prev_gov'?
> because the variable name of current governor is 'governor' instead of 'gov'.

I was trying to avoid wrapping lines too much. But this doesn't cause 
any additional wraps. Done.

> Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>

Can you please review v3?

Thanks,
Saravana

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