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SubjectRe: [BUG 3.12.rc4] Oops: unable to handle kernel paging request during shutdown
Hmm. No obvious ideas come to mind, but I'm adding more people to the cc.

Clearly the wait_event_interruptible_timeout() in the RCU grace-period
thread causes this, but I'm not seeing why shutdown would trigger it.

The code disassembles to

0: 85 db test %ebx,%ebx
2: 79 0c jns 0x10
4: 81 e6 ff 00 00 00 and $0xff,%esi
a: 8d 44 f0 30 lea 0x30(%eax,%esi,8),%eax
e: eb 0a jmp 0x1a
10: c1 e9 1a shr $0x1a,%ecx
13: 8d 84 c8 30 0e 00 00 lea 0xe30(%eax,%ecx,8),%eax
1a: 8b 48 04 mov 0x4(%eax),%ecx
1d: 89 50 04 mov %edx,0x4(%eax)
20: 89 02 mov %eax,(%edx)
22: 89 4a 04 mov %ecx,0x4(%edx)
25:* 89 11 mov %edx,(%ecx) <-- trapping instruction
27: 5b pop %ebx
28: 5e pop %esi
29: 5d pop %ebp
2a: c3 ret

so the oops is in the final

list_add_tail(&timer->entry, vec);

where "%ecx" is "vec->prev" (f8c551f4). That looks like it might be a
perfectly valid pointer, but clearly it isn't (it's about 115M off the
top of virtual memory, I think that might be in the vmalloc area).

So I'm *guessing* that something did a vfree() on some data structure
that contained active timers - and then later on the RCU thread ended
up being the next thing that tried to add a timer after the
now-non-existing one.

And your other oopses do seem to have a similar pattern, even if their
actual oops is elsewhere. They oops in run_timer_softirq, also taking
a page fault in the 0xf9...... range, so it might well be a vmalloc
address there too.

But I sure as hell can't start to guess what that would be.

I'm wondering it CONFIG_DEBUG_OBJECTS (and then
help catch this...


On Mon, Oct 14, 2013 at 4:07 AM, Knut Petersen
<> wrote:
> It愀 the third time in four months that I have to report a kernel Oops during
> shutdown.
> All of these Oopses seem somehow related to the timer subsystem, but they
> are
> not easily reproducible. As all this happens on two different machines, it愀
> unlikely
> that this mess is related to bad hardware.
> I clearly would appreciate any idea how to track this down.
> For the last two reports see:
> This time the kernel oopsed after systemd reported that target shutdown
> had been reached - see attached pdf for the full trace. To make it easier
> to find this problem a shortened call trace:
> Call Trace:
> internal_add_timer
> schedule_timeout
> ? call_timer_fn
> rcu_gp_kthread
> __init_waitqueue_head
> ? rcu_gp_fqs
> kthread
> ret_from_kernel_thread
> ? __init_kthread_worker
> EIP: __internal_add_timer
> Hardware: AOpen i915GMm-hfs mobo with a Pentium-M Dothan and 2GB of RAM.
> Distribution: openSuSE 12.3
> Kernel: local 3.12.0-rc4-00127-g45877c4 is kernel 9d05746 with my
> "Enforce 1 as lower limit for perf_event_max_sample_rate"
> patch applied.
> cu,
> knut
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