Re: [PATCH] cgroup/misc: Fix an overflow

[Haitao Huang]

Hi
On Mon, 17 Jul 2023 15:37:08 -0500, Tejun Heo <tj@xxxxxxxxxx> wrote:

> Hello,
>
> On Mon, Jul 17, 2023 at 03:19:38PM -0500, Haitao Huang wrote:
> > Actually, we are using atomic_long_t for 'current' which is the same  
> > width
> > as long defined by arch/compiler. So new_usage should be long to be
> > consistent?
>
> We can use atomic64_t, right? It's slower on 32bit machines but I think  
> it'd
> be better to guarantee resource counter range than micro-optimizing  
> charge
> operations. None of the current users are hot enough for this to matter  
> and
> if somebody becomes that hot, the difference between atomic_t and  
> atomic64_t
> isn't gonna matter that much. We'd need to batch allocations per-cpu and  
> so
> on.
>
> > ditto for event counter. Only max is plain unsigned long but I think it  
> > is
> > also OK as it only compared with 'current' without any arithmetic ops
> > involved.
> > Did I miss something here?
>
> I'm saying that it'd be better to make everything explicitly 64bit.

Thanks for the explanation. I think I got it and sent it as a separate  
patch now just to be sure.
BR
Haitao