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Re: [Xen-devel] Re: [Xen-users] Xen 4.1.1 crash when manipulating cpupoo

To: andrewpitman@xxxxxxxxxxx, George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-users] Xen 4.1.1 crash when manipulating cpupools.
From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Date: Mon, 14 Nov 2011 10:58:18 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
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On 11/14/2011 10:20 AM, Juergen Gross wrote:
On 11/11/2011 10:18 PM, andrewpitman@xxxxxxxxxxx wrote:
Juergen,

It doesn't look like this has been fixed.  I managed to get my 4.1.2 server to crash when setting the weight of Domain-0 (running in Pool-0 using credit2) and again when moving some cpus into a new cpupool which was set up to use the credit2 scheduler.

Yeah, I could reproduce your problems on my machine.

George, I see two problems in credit2:

- when setting the weight of dom0, vcpu_schedule_lock_irq(current) will be
  taken in sched_adjust() of schedule.c and again in csched_dom_cntl() of
  sched_credit2.c resulting in a deadlock.

- removing a cpu from a cpupool seems not to work for credit2. I removed all
  but cpu 0 from Pool-0 and the dom0 vcpus were all active on cpus 1-3. It
  took some time until they moved to cpu 0 (verified via 'r' hotkey on the
  xen console).

IMO the problem is choose_cpu() not using CSCHED_CPUONLINE(). The comment

        /* Leave it where it is for now.  When we actually pay attention
         * to affinity we'll have to figure something out... */

suggests the solution isn't too easy...


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
PDG ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html
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