linux-kernel - Re: [PATCH v4] video: hyperv: hyperv_fb: refresh the VM screen by force on VM panic

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Date:	Mon, 4 Aug 2014 09:36:53 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Dexuan Cui <decui@...rosoft.com>
CC:	<gregkh@...uxfoundation.org>, <plagnioj@...osoft.com>,
	<dan.carpenter@...cle.com>, <linux-kernel@...r.kernel.org>,
	<driverdev-devel@...uxdriverproject.org>,
	<linux-fbdev@...r.kernel.org>, <olaf@...fle.de>,
	<apw@...onical.com>, <jasowang@...hat.com>, <kys@...rosoft.com>,
	<haiyangz@...rosoft.com>
Subject: Re: [PATCH v4] video: hyperv: hyperv_fb: refresh the VM screen by
 force on VM panic

On 01/08/14 14:27, Dexuan Cui wrote:
> Currently the VSC has no chance to notify the VSP of the dirty rectangle on VM
> panic because the notification work is done in a workqueue, and in panic() the
> kernel typically ends up in an infinite loop, and a typical kernel config has
> CONFIG_PREEMPT_VOLUNTARY=y and CONFIG_PREEMPT is not set, so a context switch
> can't happen in panic() and the workqueue won't have a chance to run. As a
> result, the VM Connection window can't refresh until it's closed and we
> re-connect to the VM.
> 
> We can register a handler on panic_notifier_list: the handler can notify
> the VSC and switch the framebuffer driver to a "synchronous mode", meaning
> the VSC flushes any future framebuffer change to the VSP immediately.
> 
> v2: removed the MS-TFS line in the commit message
> v3: remove some 'unlikely' markings
> v4: avoid global variables as Tomi Valkeinen suggested
> 
> Cc: Haiyang Zhang <haiyangz@...rosoft.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>  drivers/video/fbdev/hyperv_fb.c | 62 +++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 59 insertions(+), 3 deletions(-)

Thanks, looks fine to me. Queuing for 3.17.

 Tomi




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