linux-kernel - Re: [PATCH] drm/rockchip: Return -EBUSY if there's already a pending flip event v5

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Date:	Tue, 24 May 2016 09:34:50 +0200
From:	Daniel Stone <daniel@...ishbar.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] drm/rockchip: Return -EBUSY if there's already a pending
 flip event v5

On 24 May 2016 at 09:27, Tomeu Vizoso <tomeu.vizoso@...labora.com> wrote:
> As per the docs, atomic_commit should return -EBUSY "if an asycnhronous
> updated is requested and there is an earlier updated pending".
>
> v2: Use the status of the workqueue instead of vop->event, and don't add
> a superfluous wait on the workqueue.
>
> v3: Drop work_busy, as there's a sizeable delay when the worker
> finishes, which introduces a race in which the client has already
> received the last flip event but the next page flip ioctl will still
> return -EBUSY because work_busy returns outdated information.
>
> v4: Hold dev->event_lock while checking the VOP's event field as
> suggested by Daniel Stone.
>
> v5: Only block if there's outstanding work if it's a blocking call.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>

Reviewed-by: Daniel Stone <daniels@...labora.com>

Cheers,
Daniel