Re: [Xen-devel] [PATCH v2 0/6] xen: simplify suspend/resume handling

[Julien Grall <julien.grall@xxxxxxx>]

On 3/28/19 1:21 PM, Juergen Gross wrote:
> On 28/03/2019 14:01, Volodymyr Babchuk wrote:
> > Hello Juergen,
> >
> > On Thu, 28 Mar 2019 at 14:09, Juergen Gross <jgross@xxxxxxxx> wrote:
> > > Especially in the scheduler area (schedule.c, cpupool.c) there is a
> > > rather complex handling involved when doing suspend and resume.
> > >
> > > This can be simplified a lot by not performing a complete cpu down and
> > > up cycle for the non-boot cpus, but keeping the pure software related
> > > state and freeing it only in case a cpu didn't come up again during
> > > resume.
> > >
> > > In summary not only the complexity can be reduced, but the failure
> > > tolerance will be even better with this series: With a dedicated hook
> > > for failing cpus when resuming it is now possible to survive e.g. a
> > > cpupool being left without any cpu after resume by moving its domains
> > > to cpupool0.
> > >
> > > Juergen Gross (6):
> > >    xen/sched: call cpu_disable_scheduler() via cpu notifier
> > >    xen: add helper for calling notifier_call_chain() to common/cpu.c
> > >    xen: add new cpu notifier action CPU_RESUME_FAILED
> > >    xen: don't free percpu areas during suspend
> > >    xen/cpupool: simplify suspend/resume handling
> > >    xen/sched: don't disable scheduler on cpus during suspend
> > >
> > >   xen/arch/arm/smpboot.c     |   4 -
> > >   xen/arch/x86/percpu.c      |   3 +-
> > >   xen/arch/x86/smpboot.c     |   3 -
> > >   xen/common/cpu.c           |  61 +++++++-------
> > >   xen/common/cpupool.c       | 131 ++++++++++++-----------------
> > >   xen/common/schedule.c      | 203 +++++++++++++++++++--------------------------
> > >   xen/include/xen/cpu.h      |  29 ++++---
> > >   xen/include/xen/sched-if.h |   1 -
> > >   8 files changed, 190 insertions(+), 245 deletions(-)
> > I tested your patch series on ARM64 platform. We had issue with hard
> > affinity - there was assertion failure in sched_credit2 code during
> > suspension if one of the vCPUs is pinned to non-0 pCPU.
> >
> > Seems, your patch series fixes the issue during suspend. But now I'm
> > seeing crash during resume:
> Oh, I wasn't aware the suspend/resume is possible on ARM, too.
We don't have suspend/resume on Arm... There are series on the ML but I 
would not consider then bug free (there was the first posting).
Cheers,

--
Julien Grall

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