Re: 6.8 powerbook g4 radeon driver kernel panic

On 2020-11-08 14:06:00 +0000 Jonathan Gray <[email protected]> wrote:

> On Sun, Nov 08, 2020 at 01:09:40PM +0000, Anthony Richardby wrote:
>> On 2020-11-08 11:14:50 +0000 Jonathan Gray <[email protected]> wrote:
>
>>> On Sun, Nov 08, 2020 at 10:51:11AM +0000, Anthony Richardby wrote:
>>> > On 2020-11-08 02:40:26 +0000 Jonathan Gray <[email protected]> wrote:
>>> > > > On Sat, Nov 07, 2020 at 04:01:34PM +0000, Anthony Richardby
>>> wrote:
>>> > > > Hey,
>>> > > > I'm experiencing a kernel panic whenever I run glxgears, or it
>>> > > would
>>> > > > seem when I try to run other gpu-related tasks. I first
>>> noticed
>>> > > this
>>> > > > when playing video via the application 'mpv', after a couple
>>> of
>>> > > > seconds of video the system freezes!! I've got the trace
>>> output
>>> > > for
>>> > > > that as the time delay allows me to switch out of X11 to a
>>> console
>>> > > > before the system crashes. Anyway after this I tried
>>> 'glxgears'
>>> > > and
>>> > > > that crashes immediately (so I'm unable to get the trace, but
>>> it
>>> > > > sounds like it's related?).
>>> > > > > Just wondering if anyone else is able to reproduce this on
>>> their
>>> > > > powerbooks / other g4 macs, does glxgears work for you?
>>> > > > > Pic of the trace output: https://postimg.cc/wRLGLKdF
>>> > > > What is the actual panic message?
>>> > > > For the archives the trace was:
>>> > > > panic(b6ae0c) at panic+0x154
>>> > > mtx_enter(0) at mtx_enter+0x8c
>>> > > drm_update_vblank_count(2a0fcdf8,e000a000,b6ae78) at
>>> > > drm_update_vblank_count+0x4b8
>>> > > drm_handle_vblank(2000611,82720e) at drm_handle_vblank+0xd8
>>> > > r100_irq_process(a19ca0) at r100_irq_process+0x110
>>> > > radeon_driver_irq_handler_kms(0) at
>>> > > radeon_driver_irq_handler_kms+0x28
>>> > > openpic_ext_intr() at openpic_ext_intr+0x274
>>> > > extint_call() at extint_call
>>> > > --- interrupt ---
>>> > > at 0xe7055e1c
>>> > > drm_wait_vblank_ioctl(e0732f00,e06b9b84,e7055c60) at
>>> > > drm_wait_vblank_ioctl+0xb2
>>> > > drm_do_ioctl(251571d0) at drm_do_ioctl+0x298
>>> > > drmioctl(25157100,e7055ca8,990000,c010643a,3a033428) at
>>> > > drmioctl+0xbc
>>> > > > >
>>> > The panic message is:
>>> > panic: mtx 0xe024cc50: locking against myself
>>> > > I forgot to mention that this is new in 6.8, I can run
>>> glxgears/play
>>> > video with mpv fine using 6.7.
>>> > The seqlock is used from an interrupt context
>>> drm_update_vblank_count() -> store_vblank()
>>> > Can you try a kernel with the following diff?
>>> Patch against 6.8 branch.
>>> > Index: sys/dev/pci/drm/drm_vblank.c
>>> ===================================================================
>>> RCS file: /cvs/src/sys/dev/pci/drm/drm_vblank.c,v
>>> retrieving revision 1.6
>>> diff -u -p -r1.6 drm_vblank.c
>>> --- sys/dev/pci/drm/drm_vblank.c	29 Jul 2020 09:52:21 -0000	1.6
>>> +++ sys/dev/pci/drm/drm_vblank.c	8 Nov 2020 11:04:58 -0000
>>> @@ -481,7 +481,7 @@ int drm_vblank_init(struct drm_device *d
>>> 		init_waitqueue_head(&vblank->queue);
>>> 		setup_timer(&vblank->disable_timer, vblank_disable_fn,
>>> 		    (unsigned long)vblank);
>>> -		seqlock_init(&vblank->seqlock, IPL_NONE);
>>> +		seqlock_init(&vblank->seqlock, IPL_TTY);
>>> 	}
>>> > 	DRM_INFO("Supports vblank timestamp caching Rev 2
>>> (21.10.2013).\n");
>>> >
>> Thanks for the time taken to look into this and offer this diff!
>> Unfortunately its still crashing, the trace and panic message look to
>> be the same:
>
>> https://postimg.cc/G4KNQ9c6
>
> I've managed to use ports clang and lldb to build and inspect a
> powerpc
> drm_vblank.o and it points to
> src/sys/dev/pci/drm/include/linux/atomic.h:165:2
> which is the ilp32 version of atomic64_read().
>
> The following patch makes sure the lock involved is initialised.
>
> Index: sys/dev/pci/drm/drm_vblank.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pci/drm/drm_vblank.c,v
> retrieving revision 1.6
> diff -u -p -r1.6 drm_vblank.c
> --- sys/dev/pci/drm/drm_vblank.c	29 Jul 2020 09:52:21 -0000	1.6
> +++ sys/dev/pci/drm/drm_vblank.c	8 Nov 2020 13:51:27 -0000
> @@ -481,7 +481,8 @@ int drm_vblank_init(struct drm_device *d
> 		init_waitqueue_head(&vblank->queue);
> 		setup_timer(&vblank->disable_timer, vblank_disable_fn,
> 		    (unsigned long)vblank);
> -		seqlock_init(&vblank->seqlock, IPL_NONE);
> +		seqlock_init(&vblank->seqlock, IPL_TTY);
> +		atomic64_set(&vblank->count, 0);
> 	}
>
> 	DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
>
>
>

Absolute rockstar! That looks to have done the trick, I've been
watching a video in mpv while running glxgears for a good 10 minutes
and everything it's still up and running.

Many thanks for your help, I'm looking forward to updating my other
machine to 6.8 now that this is working.