NULL dereference in clockevents_program_event

NULL dereference in clockevents_program_event

[Johannes Berg]

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Hi,

During a hibernate cycle on my G5, while machine was powering down after
saving the image, I just had a NULL dereference  in
clockevents_program_event when accessing dev->mode, dev was NULL.

Unfortunately the machine rebooted before I was able to write down more
than the fact that it was called from tick_program_event(); the problem
doesn't seem to be easily reproducible.

From what I can see when doing the same thing, the shutdown attempts to
offline all CPUs. Because the snapshot was actually saved to disk and
the machine was shutting down I guess that the it happened at that time,
but I have no idea what else to do to debug this.

I have

| CONFIG_HIGH_RES_TIMERS=y
| CONFIG_NO_HZ=y

in this config.

johannes

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Re: NULL dereference in clockevents_program_event

[Johannes Berg]

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> During a hibernate cycle on my G5, while machine was powering down after
> saving the image, I just had a NULL dereference  in
> clockevents_program_event when accessing dev->mode, dev was NULL.
> 
> Unfortunately the machine rebooted before I was able to write down more
> than the fact that it was called from tick_program_event(); the problem
> doesn't seem to be easily reproducible.
> 
> From what I can see when doing the same thing, the shutdown attempts to
> offline all CPUs. Because the snapshot was actually saved to disk and
> the machine was shutting down I guess that the it happened at that time,
> but I have no idea what else to do to debug this.
> 
> I have
> 
> | CONFIG_HIGH_RES_TIMERS=y
> | CONFIG_NO_HZ=y
> 
> in this config.

I just got the same or a similar thing again and was able to write down
more of the stack dump:

NIP clock_events_program_event+0x20
LR  tick_program_event+0x64
Stack:
hr_timer_interrupt+0x211
timer_interrupt+0xc4
decrementer_common+0x110

johannes

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