Re: [PATCH] mm: initialize variable for mem_cgroup_end_page_stat

[Michal Hocko <mhocko@suse.cz>]

On Thu 30-10-14 10:24:47, Sasha Levin wrote:
> On 10/30/2014 10:14 AM, Johannes Weiner wrote:
> >> The problem is that you are attempting to read 'locked' when you call
> >> > mem_cgroup_end_page_stat(), so it gets used even before you enter the
> >> > function - and using uninitialized variables is undefined.
> > We are not using that value anywhere if !memcg.  What path are you
> > referring to?
> 
> You're using that value as soon as you are passing it to a function, it
> doesn't matter what happens inside that function.

I have discussed that with our gcc guys and you are right. Strictly
speaking the compiler is free to do
if (!memcg) abort();
mem_cgroup_end_page_stat(...);

but it is highly unlikely that this will ever happen. Anyway better be
safe than sorry. I guess the following should be sufficient and even
more symmetric:
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