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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.05.19 at 15:24, <jgross@xxxxxxxx> wrote:
> On 17/05/2019 15:17, Jan Beulich wrote:
>>>>> On 08.05.19 at 13:31, <jgross@xxxxxxxx> 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.
>>>
>>> Avoid that by removing the cpu from the list of active cpus in credit2
>>> data first.
>>>
>>> The opposite problem is occurring when removing a cpu from a cpupool:
>>> init_pdata() of credit2 will access the per-cpu data of the old
>>> scheduler.
>>>
>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>> 
>> May I ask what the disposition of this is? I've noticed too late
>> that I've backported the commit being fixed here without
>> waiting for this fix to go in. I'd prefer the stable trees, in
>> particular 4.11 for the impending 4.11.2 release, to be able
>> to pick this up soon.
> 
> Dario already gave his Reviewed-by:

Oh, my fault then - apologies.

Jan



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