Re: [RFC 02/18] cgroup_pids: track maximum pids

On 06/13/16 21:33, Tejun Heo wrote:

Hello,

On Mon, Jun 13, 2016 at 09:29:32PM +0000, Topi Miettinen wrote:

quoted

I used fork callback as I don't want to lower the watermark in all cases
where the charge can be lowered, so I'd update the watermark only when
the fork really happens.

I don't think that would make a noticeable difference.  That's where
we decide whether to grant fork or not after all and thus where the
actual usage is.

You mean, increment count on cgroup_can_fork()? But what if the fork()
fails after that (signal_pending case)?

quoted

Is there a better way to compare and set? I don't think atomic_cmpxchg()
does what's needed,

cmpxchg loop should do what's necessary although I'm not sure how much
being strictly correct matters here.

Thanks.

These are not used for any decisions taken by kernel, but by the user. I
have to say I don't know where's the line between strict correctness and
less strict.

-Topi