Re: Panic and page fault in loop during handling NMI backtracehandler

[Frederic Weisbecker]

On Tue, Oct 15, 2013 at 02:01:04AM +0000, Liu, Chuansheng wrote:
> We meet one issue that during trigger all CPU backtrace, but during in the NMI handler arch_trigger_all_cpu_backtrace_handler,
> It hit the PAGE fault, then PAGE fault is in loop, at last the thread stack overflow, and system panic.
> 
> Anyone can give some help? Thanks.

Looks like we re-enter the fault several times. On x86-32, NMIs can
fault if they dereference vmalloc'ed area. I wonder if the module thing
we lookup in the NMI is stored on some vmalloc'ed area.

Also, may be we enter the fault, trigger the WARN_ON_ONCE(in_nmi()) warning,
which in turn dumps the stack, lookup that module address, refaults, etc...
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