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Re: double fault -> PAGE_KERNEL flagged memory
Mathieu Desnoyers writes:
> * Tom Zanussi (zanussi@us.ibm.com) wrote:
> > It already is PAGE_KERNEL.
>
> You are right.
>
> > The page faults you see with relayfs are
> > vmalloc page faults i.e. minor faults that just update the kernel part
> > of the current process's page table with the buffer pages.
> >
>
> Generally speaking, what would happen if :
>
> - A page fault handler has a trace point that logs an event in the RelayFS
> buffer.
> - This exact write causes a (minor) page fault.
>
> It may not happen often, but I think it would lead to a double fault. Is this
> case possible ?
>
Yes, I'm sure it is possible, in fact I'm sure it happens all the time
in LTT and it's never been a problem. Have you verified that it is a
problem (e.g. tracing only page faults and seeing a double fault).
Tom