Re: [REGRESSION 4.12] i915 Oops at intel_fbdev_invalidate()

[Takashi Iwai]

On Fri, 30 Jun 2017 17:40:43 +0200,
Chris Wilson wrote:
> 
> Quoting Takashi Iwai (2017-06-30 16:38:46)
> > Hi,
> > 
> > I hit an Oops with the latest Linus tree (4.12-rc7+) on a HSW machine
> > like the following at boot:
> > 
> >  BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
> >  IP: intel_fbdev_invalidate.isra.3+0xc/0x40 [i915]
> >  Oops: 0000 [#1] PREEMPT SMP
> >  CPU: 2 PID: 833 Comm: X Not tainted 4.10.0-rc5-btest9+ #15
> >  Hardware name: Hewlett-Packard HP ProBook 430 G1/1946, BIOS L73 Ver. 08.05 2013/03/15
> >  task: ffff917313db8000 task.stack: ffffb6e70379c000
> >  RIP: 0010:intel_fbdev_invalidate.isra.3+0xc/0x40 [i915]
> >  RSP: 0018:ffffb6e70379fde0 EFLAGS: 00010246
> >  RAX: 0000000000000000 RBX: ffff9172f70e1c00 RCX: 0000000000000000
> >  RDX: ffff917313db8000 RSI: 0000000000000000 RDI: ffff91731934d040
> >  RBP: ffffb6e70379fdf0 R08: 0000000000000002 R09: ffff91731934ead0
> >  R10: ffff9173192f0368 R11: 0000000000000001 R12: ffff9173192f0000
> >  R13: ffff9172f71016e8 R14: ffff9173227c8480 R15: ffff9172f71016c8
> >  FS:  00007f8cc8c3fa00(0000) GS:ffff9173c0a80000(0000) knlGS:0000000000000000
> >  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >  CR2: 00000000000000b0 CR3: 000000006273b000 CR4: 00000000001406e0
> >  Call Trace:
> >   ? intel_fbdev_restore_mode+0x4e/0x70 [i915]
> >   i915_driver_lastclose+0xe/0x20 [i915]
> >   drm_lastclose+0x3b/0xf0 [drm]
> >   drm_release+0x2b8/0x360 [drm]
> >   __fput+0xd9/0x1e0
> >   ____fput+0xe/0x10
> >   task_work_run+0x83/0xa0
> >   exit_to_usermode_loop+0x59/0x85
> >   do_syscall_64+0xb3/0xd0
> >   entry_SYSCALL64_slow_path+0x25/0x25
> > 
> > And git bisection leaded to the commit 
> > fabef825626d7bd05a321e4427fdf31a169b5173
> >     drm/i915: Drop struct_mutex around frontbuffer flushes
> > 
> > The band-aid patch below seems fixing it.
> 
> See https://patchwork.freedesktop.org/patch/163261/

Thanks, it worked.
  Tested-by: Takashi Iwai <tiwai@xxxxxxx>

Could you guys pick it up to for-linus?  For 4.12 it's likely too
late, but there might be a miracle.


Takashi