linux-kernel - Re: [PATCH -next v4] mm/hotplug: silence a lockdep splat with printk()

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Message-ID: <20200117024957.GA7372@google.com>
Date:   Fri, 17 Jan 2020 11:49:57 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Qian Cai <cai@....pw>
Cc:     akpm@...ux-foundation.org, mhocko@...nel.org,
        sergey.senozhatsky.work@...il.com, pmladek@...e.com,
        rostedt@...dmis.org, peterz@...radead.org, david@...hat.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH -next v4] mm/hotplug: silence a lockdep splat with
 printk()

On (20/01/16 21:21), Qian Cai wrote:
> It is not that hard to trigger lockdep splats by calling printk from
> under zone->lock. Most of them are false positives caused by lock chains
> introduced early in the boot process and they do not cause any real
> problems (although some of the early boot lock dependencies could
> happenn after boot as well). There are some console drivers which do
> allocate from the printk context as well and those should be fixed. In
> any case false positives are not that trivial to workaround and it is
> far from optimal to lose lockdep functionality for something that is a
> non-issue.
[..]
>
> Acked-by: Michal Hocko <mhocko@...e.com>
> Signed-off-by: Qian Cai <cai@....pw>

FWIW,
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

	-ss