From: Michal Hocko <mhocko@kernel.org>
To: Qian Cai <cai@lca.pw>
Cc: David Hildenbrand <david@redhat.com>,
akpm@linux-foundation.org, sergey.senozhatsky.work@gmail.com,
pmladek@suse.com, rostedt@goodmis.org, peterz@infradead.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next] mm/hotplug: silence a lockdep splat with printk()
Date: Wed, 15 Jan 2020 09:37:18 +0100 [thread overview]
Message-ID: <20200115083718.GV19428@dhcp22.suse.cz> (raw)
In-Reply-To: <D5CC7C52-1F08-401E-BDCA-DF617909BB9D@lca.pw>
On Tue 14-01-20 16:40:49, Qian Cai wrote:
>
>
> > On Jan 14, 2020, at 4:02 PM, Michal Hocko <mhocko@kernel.org> wrote:
> >
> > Yeah, that was a long discussion with a lot of lockdep false positives.
> > I believe I have made it clear that the console code shouldn't depend on
> > memory allocation because that is just too fragile. If that is not
> > possible for some reason then it has to be mentioned in the changelog.
> > I really do not want us to add kludges to the MM code just because of
> > printk deficiencies unless that is absolutely inevitable.
>
> I don’t know how to convince you, but both random number generator
> and printk() maintainers agreed to get ride of printk() with
> zone->lock held as you can see in the approved commit mentioned in
> this patch description because it is a whac-a-mole to fix other
> places.
I really do not understand this argument. It is quite a specific path in
the console code which cannot allocate any memory or use locks which
depend on the allocation via a lock chain, right? So how come this is a
whack a mole?
Also any console that really needs GFP_ATOMIC to write something out is
just inherently broken so it should better be fixed rather than
worked around.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-01-15 8:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-14 20:11 [PATCH -next] mm/hotplug: silence a lockdep splat with printk() Qian Cai
2020-01-14 20:20 ` David Hildenbrand
2020-01-14 21:02 ` Michal Hocko
2020-01-14 21:40 ` Qian Cai
2020-01-14 23:53 ` Andrew Morton
2020-01-15 1:02 ` Qian Cai
2020-01-15 1:19 ` Andrew Morton
2020-01-15 1:38 ` Qian Cai
2020-01-15 8:37 ` Michal Hocko [this message]
2020-01-15 9:52 ` Petr Mladek
2020-01-15 11:49 ` Qian Cai
2020-01-15 17:02 ` Petr Mladek
2020-01-15 17:16 ` Qian Cai
2020-01-16 14:29 ` Petr Mladek
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