Re: [Xen-devel] Help with test_and_clear_bit on events

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2011-10-04 at 11:57 +0100, Daniel Castro wrote:
> Hello List,
> 
> I have been trying for several days to be able to wait for events and
> then continue execution based on the event received. My problem is in
> the wait_ring function of xenbus.c
> After debugging my test_and_clear_bit I corrected the error that
> allows me to receive ONE event, but after that the bit is never set
> again. My offset is always 2 (nr eq 2).
> Please, can someone explain me how struct shared_info and these two
> fields control the events that I can receive?
> unsigned long evtchn_pending[sizeof(unsigned long) * 8];
> unsigned long evtchn_mask[sizeof(unsigned long) * 8];
> 
> I print the whole array Bit by Bit and I do not see a difference after
> the arrival of the event and before the arrival.
> 
> I also checked struct vcpu_info fields: u8 evtchn_upcall_pending and
> u8 evtchn_upcall_mask to see if they are disabling the event delivery.
> No changes before or after.

If git://github.com/evildani/seabios_patch.git master is up to date
then:
    shared_info = malloc_high(sizeof(shared_info));
    xatp.gpfn  = ((unsigned long)shared_info << PAGE_SHIFT);
is wrong and you aren't registering the correct shared_info so you
aren't actually looking at the right bits, the change in behaviour is
just because you are now looking at different wrong bits.

You need ">>" not "<<" (consider the relation between addresses and page
numbers...).

Ian.



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