linux-kernel - Re: [PATCH -next v5] mm/hotplug: silence a lockdep splat with printk()

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Date:   Mon, 20 Jan 2020 08:22:55 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        sergey.senozhatsky.work@...il.com, pmladek@...e.com,
        rostedt@...dmis.org, peterz@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v5] mm/hotplug: silence a lockdep splat with
 printk()

On Fri 17-01-20 11:35:08, Qian Cai wrote:
> 
> 
> > On Jan 17, 2020, at 11:27 AM, David Hildenbrand <david@...hat.com> wrote:
> > 
> > the "int" should go onto the next line as well
> > [...]
> 
> Yes.
> 
> > apart from that looks good to me. I hope we won't have a whac-a-mole
> > with printk() (including WARN_ON() etc?) under the zone lock. This all
> > screams for a better fix.
> 
> WARN_ON() is normally not a concern. Once it happens here, we will
> figure out the reason why it happens in the first place and shut it
> off there instead.

It is very much the same concern as any other printk which might
deadlock. It is true this is WARN_ONCE so the likelyhood is much
smaller. But you know, probability is not going to help you if you are
unlucky ;)

-- 
Michal Hocko
SUSE Labs