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

From: Saravana Kannan
Date: Wed Oct 26 2016 - 15:17:44 EST


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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