From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: Xen crashing when killing a domain with no VCPUs allocated Date: Mon, 21 Jul 2014 12:46:37 +0100 Message-ID: <53CCFD9D.2050502@linaro.org> References: <53C920DD.6060300@linaro.org> <1405701560.14973.1.camel@kazak.uk.xensource.com> <53C982FF.7070608@linaro.org> <53CCEC64.7040304@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53CCEC64.7040304@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap , Ian Campbell Cc: jgross@suse.com, Stefano Stabellini , Dario Faggioli , Tim Deegan , george.dunlap@citrix.com, xen-devel List-Id: xen-devel@lists.xenproject.org Hi George, On 07/21/2014 11:33 AM, George Dunlap wrote: > On 07/18/2014 09:26 PM, Julien Grall wrote: >> >> On 18/07/14 17:39, Ian Campbell wrote: >>> On Fri, 2014-07-18 at 14:27 +0100, Julien Grall wrote: >>>> Hi all, >>>> >>>> I've been played with the function alloc_vcpu on ARM. And I hit one >>>> case >>>> where this function can failed. >>>> >>>> During domain creation, the toolstack will call DOMCTL_max_vcpus >>>> which may >>>> fail, for instance because alloc_vcpu didn't succeed. In this case, the >>>> toolstack will call DOMCTL_domaindestroy. And I got the below stack >>>> trace. >>>> >>>> It can be reproduced on Xen 4.5 (and I also suspect Xen 4.4) by >>>> returning >>>> in an error in vcpu_initialize. >>>> >>>> I'm not sure how to correctly fix it. >>> I think a simple check at the head of the function would be ok. >>> >>> Alternatively perhaps in sched_mode_domain, which could either detect >>> this or could detect a domain in pool0 being moved to pool0 and short >>> circuit. >> I was thinking about the small fix below. If it's fine for everyone, I >> can >> send a patch next week. >> >> diff --git a/xen/common/schedule.c b/xen/common/schedule.c >> index e9eb0bc..c44d047 100644 >> --- a/xen/common/schedule.c >> +++ b/xen/common/schedule.c >> @@ -311,7 +311,7 @@ int sched_move_domain(struct domain *d, struct >> cpupool *c) >> } >> /* Do we have vcpus already? If not, no need to update >> node-affinity */ >> - if ( d->vcpu ) >> + if ( d->vcpu && d->vcpu[0] != NULL ) >> domain_update_node_affinity(d); > > So is the problem that we're allocating the vcpu array area, but not > putting any vcpus in it? Yes. > Overall it seems like those checks for the existence of cpus should be > moved into domain_update_node_affinity(). The ASSERT() there I think is > just a sanity check to make sure we're not getting a ridiculous result > out of our calculation; but of course if there actually are no vcpus, > it's not ridiculous at all. > > One solution might be to change the ASSERT to > ASSERT(!cpumask_empty(dom_cpumask) || !d->vcpu || !d->vcpu[0]). Then we > could probably even remove the d->vcpu conditional when calling it. This solution also works for me. Which change do you prefer? Regards, -- Julien Grall