Re: possible deadlock in lru_add_drain_all

From: Michal Hocko <mhocko@kernel.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Byungchul Park <byungchul.park@lge.com>,
	Peter Zijlstra <peterz@infradead.org>,
	syzbot
	<bot+e7353c7141ff7cbb718e4c888a14fa92de41ebaa@syzkaller.appspotmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>,
	Jerome Glisse <jglisse@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	shli@fb.com, syzkaller-bugs@googlegroups.com,
	Thomas Gleixner <tglx@linutronix.de>,
	Vlastimil Babka <vbabka@suse.cz>,
	ying.huang@intel.com, kernel-team@lge.com
Subject: Re: possible deadlock in lru_add_drain_all
Date: Wed, 14 Feb 2018 16:44:33 +0100	[thread overview]
Message-ID: <20180214154433.GD3443@dhcp22.suse.cz> (raw)
In-Reply-To: <CACT4Y+bvUmjkGDqoOGtMSBfqvbwF4=e8ZyiYYfq0kiVov8Ebiw@mail.gmail.com>

On Wed 14-02-18 15:01:38, Dmitry Vyukov wrote:
> On Thu, Nov 2, 2017 at 12:54 AM, Byungchul Park <byungchul.park@lge.com> wrote:
> > On Wed, Nov 01, 2017 at 01:01:01PM +0100, Peter Zijlstra wrote:
> >> On Wed, Nov 01, 2017 at 05:59:27PM +0900, Byungchul Park wrote:
> >> > On Tue, Oct 31, 2017 at 04:10:24PM +0100, Peter Zijlstra wrote:
> >> > > On Tue, Oct 31, 2017 at 03:58:04PM +0100, Michal Hocko wrote:
> >> > > > On Tue 31-10-17 15:52:47, Peter Zijlstra wrote:
> >> > > > [...]
> >> > > > > If we want to save those stacks; we have to save a stacktrace on _every_
> >> > > > > lock acquire, simply because we never know ahead of time if there will
> >> > > > > be a new link. Doing this is _expensive_.
> >> > > > >
> >> > > > > Furthermore, the space into which we store stacktraces is limited;
> >> > > > > since memory allocators use locks we can't very well use dynamic memory
> >> > > > > for lockdep -- that would give recursive and robustness issues.
> >> >
> >> > I agree with all you said.
> >> >
> >> > But, I have a better idea, that is, to save only the caller's ip of each
> >> > acquisition as an additional information? Of course, it's not enough in
> >> > some cases, but it's cheep and better than doing nothing.
> >> >
> >> > For example, when building A->B, let's save not only full stack of B,
> >> > but also caller's ip of A together, then use them on warning like:
> >>
> >> Like said; I've never really had trouble finding where we take A. And
> >
> > Me, either, since I know the way. But I've seen many guys who got
> > confused with it, which is why I suggested it.
> >
> > But, leave it if you don't think so.
> >
> >> for the most difficult cases, just the IP isn't too useful either.
> >>
> >> So that would solve a non problem while leaving the real problem.
> 
> 
> Hi,
> 
> What's the status of this? Was any patch submitted for this?

This http://lkml.kernel.org/r/20171116120535.23765-1-mhocko@kernel.org?

-- 
Michal Hocko
SUSE Labs