linux-kernel - Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

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Message-ID: <20171120093309.GA19627@infradead.org>
Date:   Mon, 20 Nov 2017 01:33:09 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Minchan Kim <minchan@...nel.org>,
        Huang Ying <ying.huang@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Greg Thelen <gthelen@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.

On Mon, Nov 20, 2017 at 10:25:26AM +0100, Michal Hocko wrote:
> On Fri 17-11-17 09:35:21, Christoph Hellwig wrote:
> > On Tue, Nov 14, 2017 at 06:37:42AM +0900, Tetsuo Handa wrote:
> > > Since do_shrink_slab() can reschedule, we cannot protect shrinker_list
> > > using one RCU section. But using atomic_inc()/atomic_dec() for each
> > > do_shrink_slab() call will not impact so much.
> > 
> > But you could use SRCU..
> 
> Davidlohr has tried that already http://lkml.kernel.org/r/1434398602.1903.15.camel@stgolabs.net
> and failed. Doing SRCU inside core kernel is not seen with a great
> support...

I can't actually find any objection in that thread.  What's the problem
Davidlohr ran into?