linux-kernel - Re: [PATCH 2/5] i915: flush gem obj freeing workqueues to add accuracy to the i915 shrinker

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Message-ID: <20170407100211.GG10496@nuc-i3427.alporthouse.com>
Date:   Fri, 7 Apr 2017 11:02:11 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     Martin Kepplinger <martink@...teo.de>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        daniel.vetter@...el.com, Dave Airlie <airlied@...il.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 2/5] i915: flush gem obj freeing workqueues to add
 accuracy to the i915 shrinker

On Fri, Apr 07, 2017 at 01:23:44AM +0200, Andrea Arcangeli wrote:
> Waiting a RCU grace period only guarantees the work gets queued, but
> until after the queued workqueue returns, there's no guarantee the
> memory was actually freed. So flush the work to provide better
> guarantees to the reclaim code in addition of waiting a RCU grace
> period to pass.

We are not allowed to call flush_work() from the shrinker, the workqueue
doesn't have and can't have the right reclaim flags.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre