linux-kernel - Re: Q. drm/i915 shrinker, synchronize_rcu

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Date:   Fri, 05 May 2017 12:39:40 +0300
From:   Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
To:     "J. R. Okajima" <hooanon05g@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>
Cc:     chris@...is-wilson.co.uk, daniel.vetter@...ll.ch,
        jani.nikula@...el.com, linux-kernel@...r.kernel.org
Subject: Re: Q. drm/i915 shrinker, synchronize_rcu_expedited() from handlers

On ma, 2017-05-01 at 11:05 +0900, J. R. Okajima wrote:
> Thanx for the reply.
> 
> Andrea Arcangeli:
> > 
> > Yes I already reported this, my original fix was way more efficient
> > (and also safer considering the above) than what landed upstream. My
> > feedback was ignored though.
> > 
> > https://lists.freedesktop.org/archives/intel-gfx/2017-April/125414.html
> 
> I see.
> Actually on my test system for v4.11-rc8, kthreadd, kworker, kswapd and
> others all stopped working due to the synchronize_rcu_expedited call
> from i915_gem_shrinker_count. It is definitly a show stopper for me as
> an i915 user.

Filing a bug in freedesktop.org with all the details is the fastest way
of getting help. Without the bug (and with such little information as
the previous e-mail) it's hard to estimate the extent and nature of the
bug.

I've anyway gone and prepared a patch to drop the RCU sync completely
from shrinker phase, as discussed originally with Chris.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation