From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Archit Taneja <archit@ti.com>,
linux-omap@vger.kernel.org, linux-fbdev@vger.kernel.org
Subject: Re: [PATCH 2/5] OMAPFB: simplify locking
Date: Fri, 07 Dec 2012 14:45:02 +0000 [thread overview]
Message-ID: <20121207144502.GG32230@intel.com> (raw)
In-Reply-To: <50C1F232.80508@ti.com>
On Fri, Dec 07, 2012 at 03:42:10PM +0200, Tomi Valkeinen wrote:
> On 2012-12-07 14:53, Ville Syrjälä wrote:
> > On Fri, Dec 07, 2012 at 01:55:06PM +0200, Tomi Valkeinen wrote:
> >> Kernel lock verification code has lately detected possible circular
> >> locking in omapfb. The exact problem is unclear, but omapfb's current
> >> locking seems to be overly complex.
> >>
> >> This patch simplifies the locking in the following ways:
> >>
> >> - Remove explicit omapfb mem region locking. I couldn't figure out the
> >> need for this, as long as we take care to take omapfb lock.
> >
> > I suppose the idea with that was that you wouldn't need the global
> > omapfb lock, and also it was an rwsem so it allowed parallel access to
> > the mem regions, unless the region size was being changed, in which
> > case it took the write lock. I can't really remember what the reason
> > for using an rwsem was, but I suppose there was one at the time.
>
> Right. Yes, I have no recollection either of the possible reason for it
> =). Did we have multiple concurrerent users for the fbs? It still sounds
> like a useless optimization, as all the region locks were only held for
> a short time, as far as I saw.
>
> It could also be that we're missing something from the mainline kernel,
> which we had in the Nokia kernel, and which would explain the need for
> region locks.
Yeah, perhaps there was some use for it at the time. Possibly the
zero copy video playback benefited from it in the beginning. But
IIRC almost everything was handled via the X server in the end,
so I don't think there's any compelling reason for keeping the
rwsem.
--
Ville Syrjälä
Intel OTC
next prev parent reply other threads:[~2012-12-07 14:45 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-07 11:55 [PATCH 1/5] OMAPFB: remove exported udpate window Tomi Valkeinen
2012-12-07 11:55 ` [PATCH 2/5] OMAPFB: simplify locking Tomi Valkeinen
2012-12-07 12:53 ` Ville Syrjälä
2012-12-07 13:42 ` Tomi Valkeinen
2012-12-07 14:16 ` Tomi Valkeinen
2012-12-07 14:45 ` Ville Syrjälä [this message]
2012-12-13 11:17 ` Tomi Valkeinen
2012-12-07 11:55 ` [PATCH 3/5] OMAPFB: remove warning when trying to alloc at certain paddress Tomi Valkeinen
2012-12-07 11:55 ` [PATCH 4/5] OMAPDSS: manage output-dssdev connection in output drivers Tomi Valkeinen
2012-12-07 11:55 ` [PATCH 5/5] OMAPFB: connect ovl managers to all dssdevs Tomi Valkeinen
2012-12-10 7:46 ` Archit Taneja
2012-12-10 8:03 ` Tomi Valkeinen
2012-12-10 9:55 ` Archit Taneja
2012-12-10 10:07 ` Tomi Valkeinen
2012-12-10 10:54 ` Archit Taneja
2012-12-10 11:03 ` Tomi Valkeinen
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