On 04/26/2019 06:32 AM, Joe Lawrence wrote:
> On 4/26/19 3:51 AM, Mario Smarduch wrote:
>> Hello,
>> I noticed that with livepatch the old and new functions can
>> run in parallel, but with kpatch the kpatch module load fails on
>> "activeness safety check".
>
> Hi Mario,
>
> I think you are referring to kpatch's use of stop_machine() to quiesce
> the system before patching vs. livepatch's consistency model[1] and its
> convergence on a patched state?
>
>> Am I missing something with livepatch? Is there another way to
>> build and run it?
>
> AFAIK there is no way around the consistency model with livepatch. What
> you might be able to do is hack the kpatch-build to utilize the kpatch
> support module instead of the livepatch API. (Look for the
> $KPATCH_MODULE code in the kpatch-build script.) I don't think this use
> case is very well tested and in fact, the kpatch.ko will be deprecated
> eventually.
>
> Do you have a particular case in mind which the livepatch consistency
> model does not support?
I'm also wondering if this still holds today
https://groups.google.com/forum/#!topic/fa.linux.kernel/FhGaKm0Vhm0
>
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/livepatch/livepatch.txt?h=v5.1-rc6#n63
>
>
> Regards,
>
> -- Joe
>
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