Re: Clock Interrupt not occurring. hypervisor_callback not being called. (more info)

[Dave Winchell <dwinchell@virtualiron.com>]

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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