Bug 90155

Created attachment 115292 [details]
myoops kernel module

I am using an asus laptop with intel i7 4700HQ haswell chips and intel hd 4600 gpu, those days I have experienced screen freeze when using linux kernel 3.19 and 4.0,and the magic is working, so the kernel doesn't crash.

then I found that if I use x window and there are some oops in kernel, if I do something, like move the cursor, or exit the terminal, then the screen will freeze.
(I found this problem by writing this oops module named myoops.c and insmod it, you can see attachment, you can test this by download attachment and follow those command:

tar xzvf myoops.tar.gz
cd myoops
make 
sudo insmod myoops.ko

then the screen may freeze.)

I also test above oops module on my virtualbox virtual machine and the screen won't freeze, so I think it must be the intel gpu driver's problem.

so I began to find which commit cause this problem,  I build a number of linux kernel ,finally I found the problem is cause by this patch: https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/gpu/drm/drm_fb_helper.c?id=9aa609e1a3846d3c17087b62579867bab0f488de ,

if I revert this patch and build kernel 3.19 or 4.0, and insmod the oops module, the screen won't freeze again.

So what's problem about this patch, who can help me to fix screen freeze?
I am using archlinux x86_64.