[PATCH 0/7] xen: sched: fix locking of {insert, remove}_vcpu()

[Dario Faggioli <dario.faggioli@citrix.com>]

Hi everyone,

This series originates from this other one:

 http://lists.xen.org/archives/html/xen-devel/2015-09/msg03811.html

And, more specifically, from the review subthread of patch 3 (Jan's comments,
mainly):

 http://lists.xen.org/archives/html/xen-devel/2015-09/msg03812.html
 http://lists.xen.org/archives/html/xen-devel/2015-10/msg00023.html

In fact, when reworking it, according to the review comments I got, I thought
that the locking issues in insert_vcpu() and remove_vcpu() could well deserve a
series on their own.

Both the paths (vCPU insertion and removel) suffer from locking related bugs,
which are being fixed by patches 1 and 2 of this series.  Without these two
patches, sched_move_domain() ends up doing some runqueue manipulation _without_
holding the approaprite lock, for some schedulers (which include Credit).

I haven't seen the bug trigger. Actually, I haven't tried much to mess things
up by means of it, TBH, but, in principle, it's possible.  Patches 1 and 2 are,
therefore, both candidates for being backported, I guess.

The rest of the series is basically cleanups. Patch 3 tries to make that whole
'insert vCPU' situation more clear, consistent, and easy to understand.

Patch 4 and 5 simplify both Credit2 and RTDS schedulers a (really really) small
bit, by removing the (non necessary) list of vCPUs from the scheduling specific
domain data structure, and, of course, the burden of having to manage it.

Patch 6 and 7 are, literally, (dump) output cleanups.

There is a branch available with this series applied at:

 git://xenbits.xen.org/people/dariof/xen.git  rel/sched/fix-vcpu-ins-rem
 http://xenbits.xen.org/gitweb/?p=people/dariof/xen.git;a=shortlog;h=refs/heads/rel/sched/fix-vcpu-ins-rem

Regards,
Dario
---
Dario Faggioli (7):
      xen: sched: fix locking of remove_vcpu() in credit1
      xen: sched: fix locking for insert_vcpu() in credit1 and RTDS
      xen: sched: better handle (not) inserting idle vCPUs in runqueues
      xen: sched: get rid of the per domain vCPU list in RTDS
      xen: sched: get rid of the per domain vCPU list in Credit2
      xen: sched: fix an 'off by one \t' in credit2 debug dump
      xen: sched / cpupool: dump the actual value of NOW()

 xen/common/cpupool.c       |    2 +-
 xen/common/sched_credit.c  |   17 +++++++++++--
 xen/common/sched_credit2.c |   57 +++++++++++++++-----------------------------
 xen/common/sched_rt.c      |   43 +++++++++++++--------------------
 xen/common/schedule.c      |   27 ++++++++-------------
 5 files changed, 63 insertions(+), 83 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)