linux-kernel - Re: [RFC v2 2/2] kernel/sysctl: support handling command line aliases

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Date:   Wed, 25 Mar 2020 15:44:55 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Ivan Teterevkov <ivan.teterevkov@...anix.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Guilherme G . Piccoli" <gpiccoli@...onical.com>
Subject: Re: [RFC v2 2/2] kernel/sysctl: support handling command line aliases

On Wed 25-03-20 15:36:23, Vlastimil Babka wrote:
> On 3/25/20 3:29 PM, Michal Hocko wrote:
> > Both patches look really great to me. I haven't really checked all the
> > details but from a quick glance they both seem ok.
> 
> Thanks.
> 
> > I would just add a small clarification here. Unless I am mistaken
> > early_param is called earlier than it would be now. But that shouldn't
> > cause any problems because the underlying implementation is just a noop
> > for backward compatibility.
> 
> Yeah, indeed worth noting somewhere explicitly. The conversion can't be done
> blindly, one has to consider whether the delay compared to early_param can be a
> disadvantage or not. For example the nmi_watchdog parameter is probably best
> left as it is?

I wouldn't mind moving nmi_watchdog timeout initialization to later. If
there is a usecase to rely on an early initialization then the patch can
be reverted but I struggle to think of anything reasonable. If the early
init code needs a lonter timeout to prevent from false positives then
there is clearly a bug to be better fixed. And a necessary shorter timeout
sounds quite exotic to me TBH.

-- 
Michal Hocko
SUSE Labs