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From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 7/9] drm/omap: fix omap_crtc_flush() to handle the workqueue
Date: Mon, 8 Sep 2014 16:03:18 +0300	[thread overview]
Message-ID: <540DA916.8030601@ti.com> (raw)
In-Reply-To: <20140903142750.GT15520@phenom.ffwll.local>


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On 03/09/14 17:27, Daniel Vetter wrote:
> On Wed, Sep 03, 2014 at 02:55:08PM +0300, Tomi Valkeinen wrote:
>> omap_crtc_flush() is used to wait for scheduled work to be done for the
>> give crtc. However, it's not quite right at the moment.
>>
>> omap_crtc_flush() does wait for work that is ran via vsync irq to be
>> done. However, work is also queued to the driver's priv->wq workqueue,
>> which is not handled by omap_crtc_flush().
>>
>> Improve omap_crtc_flush() to flush the workqueue so that work there will
>> be ran.
>>
>> This fixes a race issue on module unload, where an unpin work may be on
>> the work queue, but does not get ran before drm core starts tearing the
>> driver down, leading to a WARN.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> 
> I didn't really dig into details, but isn't that the same workqueue as
> used by the async modeset code? So the same deadlocks might happen ...

Yes, we have just one workqueue in the driver.

Hmm, deadlocks with what lock? The modeconfig or crtc->mutex? I don't
think they are locked at any place where omap_crtc_flush is called.

> lockdep won't complain though since you essentially open-code a
> workqueue_flush, and lockdep also doesn't complain about all possible
> deadlocks (due to some design issues with lockdep).

What do you mean "open-code a workqueue_flush"?. I use flush_workqueue
there. We have two things to wait for: work on the workqueue and work
which is triggered by the vsync irq. So we loop and test for both of
those, until there's no more work.

 Tomi



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  reply	other threads:[~2014-09-08 13:03 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-03 11:55 [PATCH 1/9] drm/omap: fix encoder-crtc mapping Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 2/9] drm/omap: page_flip: return -EBUSY if flip pending Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 3/9] drm/omap: fix race issue with vsync irq and apply Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 4/9] drm/omap: make modesetting synchronous Tomi Valkeinen
2014-09-03 14:25   ` Daniel Vetter
2014-09-03 15:05     ` Rob Clark
2014-09-03 15:21       ` Daniel Vetter
2014-09-03 16:00         ` Rob Clark
2014-09-03 19:20           ` Daniel Vetter
2014-09-08 12:53     ` Tomi Valkeinen
2014-09-08 13:24       ` Daniel Vetter
2014-09-08 13:39         ` Rob Clark
2014-09-08 13:50           ` Daniel Vetter
2014-09-08 13:57             ` Rob Clark
2014-09-03 11:55 ` [PATCH 5/9] drm/omap: clear omap_obj->paddr in omap_gem_put_paddr() Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 6/9] drm/omap: add pin refcounting to omap_framebuffer Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 7/9] drm/omap: fix omap_crtc_flush() to handle the workqueue Tomi Valkeinen
2014-09-03 14:27   ` Daniel Vetter
2014-09-08 13:03     ` Tomi Valkeinen [this message]
2014-09-08 13:31       ` Daniel Vetter
2014-09-09  7:07         ` Tomi Valkeinen
2014-09-09 10:43           ` Rob Clark
2014-09-09 10:54             ` Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 8/9] drm/omap: fix preclose to wait for scheduled work Tomi Valkeinen
2014-09-03 14:32   ` Daniel Vetter
2014-09-08 13:09     ` Tomi Valkeinen
2014-09-03 11:55 ` [PATCH 9/9] drm/omap: add a comment why locking is missing Tomi Valkeinen

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