[Bug 90155] New: [i915] linux 3.19 and 4.0 make screen freeze when there are some oops occur.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90155

            Bug ID: 90155
           Summary: [i915] linux 3.19 and 4.0  make screen freeze when
                    there are some oops occur.
           Product: DRI
           Version: XOrg git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: hzy068808 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 115292
  --> https://bugs.freedesktop.org/attachment.cgi?id=115292&action=edit
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.

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