Re: [PATCH] cgroup: Fixes the un-paired cgroup lock problem

From: Bill Davidsen
Date: Wed Nov 04 2009 - 09:27:07 EST

Li Zefan wrote:
Liu Aleaxander wrote:
From: Liu Aleaxander <Aleaxander@xxxxxxxxx>
Date: Wed, 4 Nov 2009 09:27:06 +0800
Subject: [PATCH] Fixes the un-paired cgroup lock problem

In cgroup_lock_live_group, it locks the cgroup by mutex_lock, while in the
cgroup_tasks_write, it unlock it by cgroup_unlock. Even though they are
equal, but I do think we should make it pair.

BTW, should we replace others with cgroup_lock and cgroup_unlock?
Since we already have a wrapper one and it's meaningful.

Before I read the email body, I thought there is a bug where
there is a lock without unlock or vise versa.

I agree the case here can be called "unpaired", but I'm not
convinced this patch is needed. The code is not buggy or
confusing. So the patch neither fixes a bug nor make the code
more readable.

I would say it fixes a bug, the one that would be introduced when the two methods are no longer compatible and essentially two names for the same thing. And while you may know the code so well that you knew without looking that this was (currently) okay, there will be lots of eyes on this code over the years, I think most people would find use of cgroup_lock to lock the cgroup a LOT more readable.

While you can't go back in time to murder your grandfather, it creates no paradox to fix a bug before someone writes it.

Bill Davidsen <davidsen@xxxxxxx>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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