From: Thomas Gleixner <tglx@linutronix.de>
To: Michal Hocko <mhocko@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Andrey Ryabinin <aryabinin@virtuozzo.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked()
Date: Tue, 4 Jul 2017 14:48:56 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1707041445350.9000@nanos> (raw)
In-Reply-To: <20170704105803.GK14722@dhcp22.suse.cz>
On Tue, 4 Jul 2017, Michal Hocko wrote:
> On Tue 04-07-17 11:32:33, Thomas Gleixner wrote:
> > The rework of the cpu hotplug locking unearthed potential deadlocks with
> > the memory hotplug locking code.
> >
> > The solution for these is to rework the memory hotplug locking code as well
> > and take the cpu hotplug lock before the memory hotplug lock in
> > mem_hotplug_begin(), but this will cause a recursive locking of the cpu
> > hotplug lock when the memory hotplug code calls lru_add_drain_all().
> >
> > Split out the inner workings of lru_add_drain_all() into
> > lru_add_drain_all_cpuslocked() so this function can be invoked from the
> > memory hotplug code with the cpu hotplug lock held.
>
> You have added callers in the later patch in the series AFAICS which
> is OK but I think it would be better to have them in this patch
> already. Nothing earth shattering (maybe a rebase artifact).
The requirement for changing that comes with the extra hotplug locking in
mem_hotplug_begin(). That is required to establish the proper lock order
and then causes the recursive locking in the next patch. Adding the caller
here would be wrong, because then lru_add_drain_all_cpuslocked() would be
called unprotected. Hens and eggs as usual :)
Thanks,
tglx
next prev parent reply other threads:[~2017-07-04 12:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-04 9:32 [patch V2 0/2] mm/memory_hotplug: Cure potential deadlocks vs. cpu hotplug lock Thomas Gleixner
2017-07-04 9:32 ` [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked() Thomas Gleixner
2017-07-04 10:58 ` Michal Hocko
2017-07-04 12:48 ` Thomas Gleixner [this message]
2017-07-04 12:52 ` Michal Hocko
2017-07-04 12:07 ` Vlastimil Babka
2017-07-04 12:35 ` Thomas Gleixner
2017-07-04 9:32 ` [patch V2 2/2] mm/memory-hotplug: Switch locking to a percpu rwsem Thomas Gleixner
2017-07-04 10:59 ` Michal Hocko
2017-07-04 12:10 ` Vlastimil Babka
2017-07-04 12:49 ` Thomas Gleixner
2017-07-04 15:01 ` Davidlohr Bueso
2017-07-04 15:22 ` Davidlohr Bueso
2017-07-04 15:32 ` Thomas Gleixner
2017-07-04 15:42 ` Davidlohr Bueso
2017-07-05 21:53 ` [patch V2 0/2] mm/memory_hotplug: Cure potential deadlocks vs. cpu hotplug lock Andrew Morton
2017-07-06 6:34 ` Thomas Gleixner
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