Jan Kiszka wrote:
> Jan Kiszka wrote:
>> It's still unclear what goes on precisely, we are still digging, but the
>> test system that can produce this is highly contended.
> 
> Short update: Further instrumentation revealed that cr3 differs from
> active_mm->pgd while we are looping over that fault, ie. the kernel
> tries to fixup the wrong mm. And that means we have some open race
> window between updating cr3 and active_mm somewhere (isn't switch_mm run
> in a preemptible manner now?).
> 
> As a first shot I disabled CONFIG_IPIPE_DELAYED_ATOMICSW, and we are now
> checking if it makes a difference. Digging deeper into the code in the
> meanwhile...

CONFIG_IPIPE_DELAYED_ATOMICSW is nonsense. And we don't do switch_mm
without irq protection on x86, at least not from the nucleus, right?
Maybe a race due some Linux user running it unprotectedly?

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

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