Re: [Xen-devel] [PATCH v3 07/23] xsplice: Implement support for applying/reverting/replacing patches. (v5)

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 02/16/2016 07:11 PM, Andrew Cooper wrote:
snip
> > +        }
> > +
> > +        barrier(); /* MUST do it after get_cpu_maps. */
> > +        total_cpus = num_online_cpus() - 1;
> > +
> > +        if ( total_cpus )
> > +        {
> > +            printk(XENLOG_DEBUG "%s: CPU%u - IPIing the %u CPUs.\n", p->name,
> > +                   cpu, total_cpus);
> > +            smp_call_function(reschedule_fn, NULL, 0);
> > +        }
> > +        (void)xsplice_do_single(total_cpus);
> > +
> > +        ASSERT(local_irq_is_enabled());
> > +
> > +        put_cpu_maps();
> > +
> > +        printk(XENLOG_DEBUG "%s finished with rc=%d\n", p->name, p->rc);
> > +    }
> > +    else
> > +    {
> > +        /* Wait for all CPUs to rendezvous. */
> > +        while ( xsplice_work.do_work && !xsplice_work.ready )
> > +        {
> > +            cpu_relax();
> > +            smp_rmb();
> > +        }
> > +
> What happens here if the rendezvous initiator times out?  Looks like we
> will spin forever waiting for do_work which will never drop back to 0.
xsplice_do_wait() sets do_work to 0 on a timeout.

--
Ross Lagerwall

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