[v2,0/4] xen: sched: support vcpu hotplug/hotunplug in the 'null scheduler'

Message

Dario Faggioli July 26, 2019, 6:25 a.m. UTC

Hello,

Here it is v2 of my series, about fixing vcpu off- and on-lining in the
null scheduler, recently reviewed by George.

v1 posting is here:
https://lists.xenproject.org/archives/html/xen-devel/2018-08/msg02182.html
Message-Id: <[e-mail]>

Basically, it turned out, while discussing this patch:
https://lists.xenproject.org/archives/html/xen-devel/2018-01/msg00249.html

that the 'null scheduler' does not really support vcpu
hotplug/hotunplug. In fact, under some circumnstances, it is possible
that the vcpus which are actually offline, get assigned to a pcpu, while
one or more online vcpus, may be left in the wait list, and stay there
forever.

One of these circumnstances was, for instance, when the 'null scheduler'
was used within the PV-SHIM, but the problem is more general, and this
series fixes it.

I think I've addressed Goerge's comments. The most notable change is the
merge of what in v1 were patch 2 and patch 3. The resulting patch (i.e.,
patch 2 of this series) is the only one missing an Ack to go in.

The series is also available in git:
git://xenbits.xen.org/people/dariof/xen.git  rel/sched/null-fix-vcpu-hotplug-v2

Thanks and Regards,
Dario
---
Dario Faggioli (4):
      xen: sched: refector code around vcpu_deassign() in null scheduler
      xen: sched: deal with vCPUs being or becoming online or offline
      xen: sched: reassign vCPUs to pCPUs, when they come back online
      xen: sched: refactor the ASSERTs around vcpu_deassing()

 xen/common/sched_null.c |  210 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 152 insertions(+), 58 deletions(-)
--
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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