linux-kernel - Re: [PATCH net] net: memcontrol: charge allocated memory after mem_cgroup_sk

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Date:   Thu, 1 Feb 2018 23:42:33 +0000
From:   Roman Gushchin <guro@...com>
To:     Eric Dumazet <edumazet@...gle.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...com>,
        Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH net] net: memcontrol: charge allocated memory after
 mem_cgroup_sk_alloc()

On Thu, Feb 01, 2018 at 03:27:14PM -0800, Eric Dumazet wrote:
> Well, this memcg stuff is so confusing.
> 
> My recollection is that we had :
> 
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=d979a39d7242e0601bf9b60e89628fb8ac577179
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=75cb070960ade40fba5de32138390f3c85c90941
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=c0576e3975084d4699b7bfef578613fb8e1144f6
> 
> And commit a590b90d472f2c176c140576ee3ab44df7f67839 as well
> 
> Honestly bug was closed months ago for us, based on stack traces on the wild.
> 
> No C repro or whatever, but reproducing it would be a matter of
> having a TCP listener constantly doing a
> socket()/setsockopt(REUSEADDR)/bind()/listen()/close() in a loop,
> while connections are attempted to the listening port.

Oh, I see...

Then I think that we should return memcg_sk_alloc() back to the bh context,
where cgroup_sk_alloc() is, and repeat all the tricks to avoid copying
dead cgroups/memcg pointers. Do you agree?

I'll try to master a patch and reproduce the issue.

Thanks!