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@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.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