linux-kernel - Re: [PATCH 2/2] ARC: show_regs: fix lockdep splat for good

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Date:   Fri, 21 Dec 2018 14:27:53 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Vineet Gupta <vineet.gupta1@...opsys.com>
Cc:     "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/2] ARC: show_regs: fix lockdep splat for good

On Fri 21-12-18 14:04:04, Michal Hocko wrote:
[...]
> Yes, but you are building on a broken concept I believe. What
> implications does re-enabling really have? Now you could reschedule and
> you can move to another CPU. Is this really safe? I believe that yes
> because the preemption disabling is simply bogus. Which doesn't sound
> like a proper justification, does it?

Well, thinking about it a bit more. What is the result of calling
preempt_enable outside of preempt_disabled section? E.g. __warn which
doesn't disable preemption AFAICS.
-- 
Michal Hocko
SUSE Labs