lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 4 Jul 2017 14:52:26 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked()

On Tue 04-07-17 14:48:56, Thomas Gleixner wrote:
> 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 :)

Yeah, you are right. My bad I should have noticed that.
-- 
Michal Hocko
SUSE Labs

Powered by blists - more mailing lists