linux-kernel - Re: [PATCH 1/7] cgroup: Implement cgroup_show

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Message-ID: <ZszK1zQJSjuEO4r5@slm.duckdns.org>
Date: Mon, 26 Aug 2024 08:35:03 -1000
From: Tejun Heo <tj@...nel.org>
To: Michal Koutný <mkoutny@...e.com>
Cc: void@...ifault.com, peterz@...radead.org, mingo@...hat.com,
	cgroups@...r.kernel.org, lizefan.x@...edance.com,
	hannes@...xchg.org, kernel-team@...a.com,
	linux-kernel@...r.kernel.org, David Vernet <dvernet@...a.com>,
	Josh Don <joshdon@...gle.com>, Hao Luo <haoluo@...gle.com>,
	Barret Rhoden <brho@...gle.com>
Subject: Re: [PATCH 1/7] cgroup: Implement cgroup_show_cftypes()

Hello, Michal.

On Tue, Aug 20, 2024 at 04:38:40PM +0200, Michal Koutný wrote:
> On Wed, Aug 07, 2024 at 02:25:23PM GMT, Tejun Heo <tj@...nel.org> wrote:
> > +void cgroup_show_cftype(struct cftype *cft, bool show)
> > +{
> > +	struct cgroup_subsys *ss = cft->ss;
> > +	struct cgroup *root = ss ? &ss->root->cgrp : &cgrp_dfl_root.cgrp;
> 
> Strictly speaking, this (v1) cgroup_root dereference should be guarded
> with cgroup_mutex too (should be the root destroy concurrently).

Ah, right. I think I might just drop this patch. Hiding and showing the
interface files dynamically doesn't seem to work that well in practive (ie.
it causes more production problems than it solves). Something a bit more
boring like triggering a warning when a unimplemented feature is used is
probably better here.

Thanks.

-- 
tejun