Re: [PATCH] mm: fix up a spurious page fault whenever it happens

[Peter Zijlstra]

On Wed, Jun 19, 2013 at 09:36:39AM +0200, Stanislav Meduna wrote:
> On 19.06.2013 07:20, Linus Torvalds wrote:
> 
> >> No crash in 2 days running with preempt none...
> > 
> > Is this UP?
> 
> Yes it is.
> 
> > There's the fast_tlb race that Peter fixed in commit 29eb77825cc7
> > ("arch, mm: Remove tlb_fast_mode()"). I'm not seeing how it would
> > cause infinite TLB faults, but it definitely causes potentially
> > incoherent TLB contents. And afaik it only happens with
> > CONFIG_PREEMPT, and on UP systems. Which sounds like it might match
> > your setup...
> 
> Oh, thank you for the pointer, this indeed looks interesting.
> 
> Unfortunately the patch massively does not apply to 3.4 which
> I am using and I know too little what all is involved here
> to backport it. I will test it when (if) it gets to the 3.4(-rt)
> (or when I find some spare time to play with the newer kernel
> on that system).

The easiest way to test for your system is to ensure tlb_fast_mode()
return an unconditional 0.
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