Re: [lhcs-devel] Re: in_atomic doesn't count local_irq_disable?

[Manfred Spraul]

Srivatsa Vaddagiri wrote:

> More debugging reveals that the page fault happens
> always while doing a prefetch. The prefetch is
> present inside list_for_each_entry macros.
>
> For now I have disabled the x86 prefetch function
> to do nothing.
>
> The test seems to run fine so far w/o any of the 
> page faults I was experiencing. Will update
> at the end of the overnight run if I hit the problem again.
>
> Wonder if prefetch has some issues on Intel x86 (P3) SMP systems?
>  
Hmm. Perhaps prefetch updates CR2?
We know already that the CR2 is not directly linked to the page fault 
interrupt - if a page fault happens at the same time as a higher 
priority event (iirc hw interrupt), then CR2 is updated and the higher 
priority event is handled. That prevents Linux from using CR2 to store 
the cpu number - only netware can do that, because netware never causes 
paging faults.

Could you write a test module that reads cr2, executes a few prefetch 
instructions and then checks if cr2 changed? I won't have access to my 
P3 SMP system in the next few days.

--
   Manfred


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