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Date:   Wed, 3 Feb 2021 14:04:15 +0100
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     dri-devel@lists.freedesktop.org, Dave Airlie <airlied@redhat.com>,
        David Airlie <airlied@linux.ie>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@lists.linux-foundation.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 5/5] drm/qxl: properly free qxl releases
Message-ID: <20210203130415.rqokinkpy6ivixmu@sirius.home.kraxel.org>
References: <20210126165812.1661512-1-kraxel@redhat.com>
 <20210126165812.1661512-6-kraxel@redhat.com>
 <YBp3zQqomQziZbPT@phenom.ffwll.local>
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> > +	/*
> > +	 * Ask host to release resources (+fill release ring),
> > +	 * then wait for the release actually happening.
> > +	 */
> > +	qxl_io_notify_oom(qdev);
> > +	for (try = 0; try < 20 && atomic_read(&qdev->release_count) > 0; try++)
> > +		msleep(20);
> 
> A bit icky, why not use a wait queue or something like that instead of
> hand-rolling this? Not for perf reasons, just so it's a bit clear who
> waits for whom and why.

There isn't one ready for use, and adding a new one (to wait for the
garbage collection having released something) just for a clean shutdown
looked a bit like overkill.

But after digging a bit more and looking at the qxl_fence_wait() mess I
think adding a wait queue looks like a good idea ...

v5 coming soon ...

take care,
  Gerd