linux-kernel - Re: [PATCH v2 6/8] mm/lru: remove rcu_read

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: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20191113114045.GZ3016@techsingularity.net>
Date:   Wed, 13 Nov 2019 11:40:46 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     Matthew Wilcox <willy@...radead.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, tj@...nel.org, hughd@...gle.com,
        khlebnikov@...dex-team.ru, daniel.m.jordan@...cle.com,
        yang.shi@...ux.alibaba.com, Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Chris Down <chris@...isdown.name>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 6/8] mm/lru: remove rcu_read_lock to fix performance
 regression

On Wed, Nov 13, 2019 at 10:40:58AM +0800, Alex Shi wrote:
> 
> 
> ?? 2019/11/12 ????10:38, Matthew Wilcox ????:
> > On Tue, Nov 12, 2019 at 10:06:26PM +0800, Alex Shi wrote:
> >> Intel 0day report there are performance regression on this patchset.
> >> The detailed info points to rcu_read_lock + PROVE_LOCKING which causes
> >> queued_spin_lock_slowpath waiting too long time to get lock.
> >> Remove rcu_read_lock is safe here since we had a spinlock hold.
> > Argh.  You have not sent these patches in a properly reviewable form!
> > I wasted all that time reviewing the earlier patch in this series only to
> > find out that you changed it here.  FIX THE PATCH, don't send a fix-patch
> > on top of it!
> > 
> 
> Hi Matthew,
> 
> Very sorry for your time! The main reasons I use a separate patch since a, Intel 0day asking me to credit their are founding, and I don't know how to give a clearly/elegant explanation for a non-exist regression in a fixed patch. b, this regression is kindly pretty tricky.  Maybe it's better saying thanks in version change log of cover-letter?
> 

Add something like this to the patch

[lkp@...el.com: Fix RCU-related regression reported by LKP robot]
Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
...

-- 
Mel Gorman
SUSE Labs