linux-kernel - Re: [PATCH v8 3/4] cgroups: allow a cgroup subsystem to reject a fork

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Message-ID: <20150406150536.GA10582@htj.duckdns.org>
Date:	Mon, 6 Apr 2015 11:05:36 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Aleksa Sarai <cyphar@...har.com>
Cc:	lizefan@...wei.com, mingo@...hat.com, peterz@...radead.org,
	richard@....at,
	Frédéric Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH v8 3/4] cgroups: allow a cgroup subsystem to reject a fork

Hello, Aleksa.

On Fri, Apr 03, 2015 at 10:42:27AM +1100, Aleksa Sarai wrote:
> I tried doing this and the kernel would refuse to boot. I believe it has
> something to do with the ordering of early_init subsystems, but I'm not

Hmmm... yeah, failure in early_init can be tricky to debug.

> entirely sure (this optimisation can be dealt with later [it's non-critical],
> so IMO this should be done in a separate patchset [if at all]). Also, your
> later comments would fix the subsys bitmask problem (we can just pass the
> default %NULL), we don't even need to test the index.

But we'd be adding quite a few loops in relatively hot paths.  I don't
think it's a good idea to send the patches as-are because we can't
debug and fix them properly, right?  If there are hard ordering
dependencies, the range of subsystems which require fork/exit doesn't
have to be at the beginning.

Thanks.

-- 
tejun
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