Re: [Xen-devel] [PATCH] xen/sched: fix csched2_deinit_pdata()

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Wed, 2019-05-08 at 13:31 +0200, Juergen Gross wrote:
> Commit 753ba43d6d16e688 ("xen/sched: fix credit2 smt idle handling")
> introduced a regression when switching cpus between cpupools.
> 
> When assigning a cpu to a cpupool with credit2 being the default
> scheduler csched2_deinit_pdata() is called for the credit2 private
> data
> after the new scheduler's private data has been hooked to the per-cpu
> scheduler data. Unfortunately csched2_deinit_pdata() will cycle
> through
> all per-cpu scheduler areas it knows of for removing the cpu from the
> respective sibling masks including the area of the just moved cpu.
> This
> will (depending on the new scheduler) either clobber the data of the
> new scheduler or in case of sched_rt lead to a crash.
> 
These issues will drive us all crazy, at some point! :-(

I really wish I managed to put a cpupool test in OSSTest. I guess I can
pickup my old draft, but I need some time to put together an OSSTest
dev environment again. :-/

Anyway...

> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>
Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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