From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Date: Tue, 24 Jun 2014 13:51:01 +0000 Subject: Re: [PATCH] video: hyperv: hyperv_fb: refresh the VM screen by force on VM panic Message-Id: <20140624135101.GB10115@kroah.com> List-Id: References: <1403569757-2622-1-git-send-email-decui@microsoft.com> In-Reply-To: <1403569757-2622-1-git-send-email-decui@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dexuan Cui Cc: linux-fbdev@vger.kernel.org, jasowang@redhat.com, driverdev-devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, tomi.valkeinen@ti.com, olaf@aepfle.de, apw@canonical.com, plagnioj@jcrosoft.com, haiyangz@microsoft.com On Tue, Jun 24, 2014 at 08:29:17AM +0800, 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. > > MS-TFS: 157532 What is this line for? thanks, greg k-h