Re: [Xen-devel] [PATCH v2] Fix scheduler crash after s3 resume

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>]

Am 25.01.2013 11:15, schrieb Jan Beulich:
> > > > On 25.01.13 at 10:45, Tomasz Wroblewski<tomasz.wroblewski@xxxxxxxxxx>  wrote:
> > > I think I had already raised the question of the placement of
> > > this rcu_barrier() here, and the lack of a counterpart in the
> > > suspend portion of the path. Keir? Or should
> > > rcu_barrier_action() avoid calling process_pending_softirqs()
> > > while still resuming, and instead call __do_softirq() with all but
> > > RCU_SOFTIRQ masked (perhaps through a suitable wrapper,
> > > or alternatively by open-coding its effect)?
> > Though I recall these vcpu_wake crashes happen also from other entry
> > points in enter_state but rcu_barrier, so I dont think removing that
> > helps much. Just was unable to get a proper log of them today due to
> > most of them being cut in half. Will try bit more.
> In which case making __do_softirq() itself honor being in the
> suspend/resume path might still be an option.
>
> > My belief is that as long as vcpu_migrate is not called in
> > cpu_disable_scheduler, the vcpu->processor shall continue to point to
> > offline cpu. Which will crash if the vcpu_wake is called for that vcpu.
> > If vcpu_migrate is called, then vcpu_wake will still be called with some
> > frequency but since vcpu->processor shall point to online cpu, and it
> > won't crash. So likely avoiding the wakes here completely is not the
> > goal, just the offline ones.
> But you neglect the fact that waking vCPU-s at this point is
> unnecessary anyway (they have nowhere to run on).
What about adding a global scheduler_disable() in freeze_domains() and a 
scheduler_enable() in thaw_domains() which will switch scheduler locking to
a global lock (or disable it at all?). This should solve all problems without
any complex changes of current behavior.


Juergen

--
Juergen Gross                 Principal Developer Operating Systems
PBG 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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel