linux-kernel - Re: [Spice-devel] [PATCH 09/11] Move main reference counter to GEM object instead of TTM ones

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Message-ID: <CAPM=9txWjm_nY=7t3OvfF2yB1YmikyTA8u9cB7x+6FU2hL6rsw@mail.gmail.com>
Date:	Thu, 28 May 2015 13:31:16 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Frediano Ziglio <fziglio@...hat.com>
Cc:	spice-devel <spice-devel@...ts.freedesktop.org>,
	Dave Airlie <airlied@...ux.ie>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Dave Airlie <airlied@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Spice-devel] [PATCH 09/11] Move main reference counter to GEM
 object instead of TTM ones

On 27 May 2015 at 20:04, Frediano Ziglio <fziglio@...hat.com> wrote:
> qxl_bo structure has two reference counters, one in the GEM object and
> another in the TTM object. The GEM object keep a counter to the TTM object
> so when GEM counter reached zero the TTM counter (using qxl_bo_unref) was
> decremented. The qxl object is fully freed (both GEM and TTM part are cleaned)
> when the TTM counter reach zero.
> One issue was that surface idr structure has no owning on qxl_bo objects however
> it contains a pointer to qxl_bo object. This caused some nasty race condition
> for instance qxl_bo object was reaped even after counter was already zero.
> This patch fix these races moving main counter (the one used by qxl_bo_(un)ref)
> to GEM object which cleanup routine (qxl_gem_object_free) remove the idr pointer
> (using qxl_surface_evict) when the counters are still valid.

Uggh, but yes, not sure I like this fix for the problem, but if it works,

Reviewed-by: Dave Airlie <airlied@...hat.com>
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