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[Xen-devel] [PATCH v2 0/6] xen: RCU: x86/ARM: Add support of rcu_idle_{enter, exit}


This is take 2 of this series, v1 of which can be found here:


This new version is mostly about taking care of the various review comments
received. Something of the differences are worth a mention here, though:

- patch 3 is significantly different, as a consequence of the fact that Tim
  highlighted, during v1 review, that there was another latent race that we
  should deal with. Luckily, it basically "was enough" to move the invocations
  of rcu_idle_{enter,exit}() a bit, and add some barriers (details in the
  patch changelog);

- patch 6 has been added, in the attempt of addressing concerns (coming mainly
  from Stefano) about the fact that the timer we need to introduce to deal
  with idle CPUs with queued callbacks, may be firing too often (leading to
  power being wasted).

There is a git branch, with this series in it, available here:


This patch series addresses the XEN-27 issue, which I think Julien wants to
consider a blocker for 4.10:


Thanks and Regards,

Dario Faggioli (6):
      xen: in do_softirq() sample smp_processor_id() once and for all.
      xen: ARM: suspend the tick (if in use) when going idle.
      xen: RCU/x86/ARM: discount CPUs that were idle when grace period started.
      xen: RCU: don't let a CPU with a callback go idle.
      xen: RCU: avoid busy waiting until the end of grace period.
      xen: try to prevent idle timer from firing too often.

 xen/arch/arm/domain.c         |   29 ++++++---
 xen/arch/x86/cpu/mwait-idle.c |    3 -
 xen/common/rcupdate.c         |  130 ++++++++++++++++++++++++++++++++++++++++-
 xen/common/schedule.c         |    4 +
 xen/common/softirq.c          |    8 +--
 xen/include/xen/perfc_defn.h  |    2 +
 xen/include/xen/rcupdate.h    |    6 ++
 xen/include/xen/sched.h       |    6 +-
 8 files changed, 166 insertions(+), 22 deletions(-)
<<This happens because I choose it to happen!>> (Raistlin Majere)
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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