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

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Message-ID: <20200116142954.l6gttssy65tuwygd@pathway.suse.cz>
Date:   Thu, 16 Jan 2020 15:29:54 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Qian Cai <cai@....pw>
Cc:     Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        sergey.senozhatsky.work@...il.com, rostedt@...dmis.org,
        peterz@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] mm/hotplug: silence a lockdep splat with printk()

On Wed 2020-01-15 12:16:17, Qian Cai wrote:
> 
> 
> > On Jan 15, 2020, at 12:02 PM, Petr Mladek <pmladek@...e.com> wrote:
> > 
> > On Wed 2020-01-15 06:49:03, Qian Cai wrote:
> >> 
> >> 
> >>> On Jan 15, 2020, at 4:52 AM, Petr Mladek <pmladek@...e.com> wrote:
> >>> 
> >>> I could understand that Michal is against hack in -mm code that
> >>> would just hide a false positive warning.
> >> 
> >> Well, I don’t have any confidence to say everything this patch is
> >> trying to fix is false positives.
> > 
> > You look at this from a wrong angle. AFAIK, all lockdep reports pasted
> > in the below mentioned thread were false positives. Now, this patch
> > complicates an already complicated -mm code to hide the warning
> > and fix theoretical problems.
> 
> What makes you say all of those are false positives?

I have to admit that the 3 provided lockdep reports really looked
suspicious. I must have somehow missed/forgot about them.

If the last proposed change removes them and is acceptable for -mm
people then it looks like a reasonable solution.

Best Regards,
Petr