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

[Daniel Castro <evil.dani@xxxxxxxxx>]

On Tue, Oct 4, 2011 at 8:02 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 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...).

Thanks, sorry for the typo, I just corrected it, the same behavior persists.

The output for shinfo->evtchn_pending[2] is
11001100110011001100110011001100, which bit am I supposed to change?
Here I am confused.
Also I have: VCPU.0 evtchn_upcall_mask 11000010 AND evntchn_pending 11000010

Sorry but I am somewhat confused by all this. Is this documented somewhere?

Million Thanks again!

>
> Ian.
>
>
>



-- 
+-=====---------------------------+
| +---------------------------------+ | This space intentionally blank
for notetaking.
| |   | Daniel Castro,                |
| |   | Consultant/Programmer.|
| |   | U Andes                         |
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