On Tue, Oct 15, 2013 at 06:06:59AM -0700, Paul E. McKenney wrote: > On Tue, Oct 15, 2013 at 02:59:15PM +0200, Frederic Weisbecker wrote: > > On Tue, Oct 15, 2013 at 05:48:37AM -0700, Paul E. McKenney wrote: > > > On Tue, Oct 15, 2013 at 02:37:17PM +0200, Peter Zijlstra wrote: > > > > On Tue, Oct 15, 2013 at 02:18:53PM +0200, Frederic Weisbecker wrote: > > > > > 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. > > > > > > > > IIRC modules are indeed allocated using vmalloc. See module_alloc() > > > > using vmalloc_exec() > > > > > > This might then be a module that uses call_rcu(), but which does not have > > > the needed rcu_barrier() in the module-exit function. > > > > I rather believe it's due to the lazy paging of vmalloc area in x86-32. We > > had issues > > like that in the past. For example that's the reason why we do an ad-hoc > > per-cpu > > allocation on callchain buffers in perf rather than using alloc_percpu() > > which might > > use vmalloc. > > I must defer to your greater experience with this type of bug.
With some chances I'll be proved wrong. I hope, because that issue is not easily fixed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
