Re: [Xen-devel] Clock Interrupt not occurring. hypervisor_callback not being called. (more info)

[Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>]

Ivan,

How about a memory barrier right before the call to evtchn_notify
in evtchn_set_pending and one before l1 = 
x86_atomic_xchg(&s->evtchn_pending_sel, 0)
in do_hypervisor_callback?

Regards,
Dave


Ivan Kelly wrote:

> Some more info on this problem.
> The problem seems to be that evtchn_pending[0] is not being updated
> fast enough after the callback is made. Therefore the callback is
> running and seeing nothing as pending and discarding anything that
> happens.
> If i put in something that delays before the start of the inner loop
> somewhere, it will work fine. It doesn't have to be a printf, can be a
> for(i=0;i<100000;i++) or something similar.
> evtchn_pending is set as volatile. Im not sure if this is actually
> helping at all though, since I have to use the ACK compiler which is
> the only thing that minix will compile with.
>
> Does anyone have any idea on how i can get evtchn_pending to update on time?
> Regards
> Ivan
>
>  
>
> > <SNIP>
> > PUBLIC void
> > do_hypervisor_callback(struct stackframe_s *regs)
> > {
> >        unsigned long  l1, l2;
> >        unsigned int   l1i, l2i, port;
> >        int            irq;
> >        shared_info_t *s = hypervisor_shared_info;
> >
> >        s->vcpu_data[0].evtchn_upcall_pending = 0;
> >
> >        l1 = x86_atomic_xchg(&s->evtchn_pending_sel, 0);
> >
> >        while ( l1 != 0 )
> >        {
> > /*              kprintf("l1: %x\n");*/
> >                l1i = x86_scan_forward(l1);
> >                l1 &= ~(1 << l1i);
> >
> >                l2 = s->evtchn_pending[l1i] & ~s->evtchn_mask[l1i];
> >                while ( l2 != 0 )
> >                {
> >                        kprintf("l2: %x\n", l2);
> >                        l2i = x86_scan_forward(l2);
> >                        l2 &= ~(1 << l2i);
> >
> >                        port = (l1i << 5) + l2i;
> >
> >                        if ( (irq = event_to_action[port]) != -1 ) {
> >                                do_event(irq, regs);
> >                        }
> >                }
> >        }
> > }
> > <ENDSNIP>
> >
> >    
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>  

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