Re: [Xen-devel] Debug event_channel.c

[Daniel Castro <evil.dani@xxxxxxxxx>]

On Thu, Sep 29, 2011 at 8:30 PM, Ian Campbell
<Ian.Campbell@xxxxxxxxxxxxx> wrote:
> On Thu, 2011-09-29 at 12:09 +0100, Daniel Castro wrote:
>> On Tue, Sep 27, 2011 at 9:09 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
>> wrote:
>> > On Tue, 2011-09-27 at 12:36 +0100, Daniel Castro wrote:
>> >> On Tue, Sep 27, 2011 at 8:33 PM, Andrew Cooper
>> >> <andrew.cooper3@xxxxxxxxxx> wrote:
>> >> > On 27/09/11 12:09, Daniel Castro wrote:
>> >> >> Hello All,
>> >> >>
>> >> >> I am trying to debug event_channel.c for this I have filled the
>> >> >> functions with gdprintk(XENLOG_WARNING, "..."); yet the messages are
>> >> >> not displayed on dmesg or /var/log/xen. Where could they be printed?
>> >> >> or should I use a different function?
>> >> >>
>> >> >> In grub I have loglvl=all to print all messages...
>> >> >>
>> >> >> Thanks for the answer,
>> >> >>
>> >> >> Daniel
>> >> >>
>> >> >
>> >> > gdprintk only gets set with guest debugging enabled. ( guest_loglvl on
>> >> > the command line )
>> >> >
>> >> > My suggestion would be to just use regular printks and look at the
>> >> > serial log.
>> >>
>> >> How can can I look at the serial log from dom0?
>> >
>> > 'xl dmesg' (or using a serial cable of course ;-))
>> >
>> > You can also add XENCONSOLED_TRACE=hv in /etc/sysconfig/xencommons (or
>> > the equivalent on your distro, the effect should be to add --log=hv to
>> > the xenconsoled command line). Then the xen console will be logged
>> > under /var/log/xen somewhere.
>>
>> Ian, thanks for the info.
>>
>> This is the info I gathered:
>> (XEN) schedule.c:658:d1 DEBUG 1: START DO POLL port -32060 on
>> sched_poll.nr_ports 1
>
> port == -32060 doesn't sound right...
>
>> (XEN) schedule.c:719:d1 DEBUG 1: DO POLL test bit on port 2 exit here
>> -> if ( test_bit(port, &shared_info(d, evtchn_pending)) )
>> (XEN) schedule.c:746:d1 DEBUG 1: DO POLL GOTO out: check previus msg,
>> return rc=0
>> (XEN) event_channel.c:606:d1 DEBUG 1: set_pending
>> (XEN) event_channel.c:628:d1 DEBUG 1 : evtchn_set_pending test_bit AND
>> test_and_set_bit returned 0.
>> (XEN) event_channel.c:637:d1 DEBUG 1: evtchn_set_pending bitmap_empty return 
>> 0.
>>
>> In my code test_bit_and_clear in Xenstore ring_wait is in fact
>> returning 0, it was expecting a one, the do_poll is finding the bit in
>> 1 also according to test_bit, right?
>> So the error is on the my test_bit_and_clear. Am I reading it correctly?
>
> I'm not sure I follow what your debug messages are actually saying, but
> if do_poll is exiting because of the
>        if ( test_bit(port, &shared_info(d, evtchn_pending)) )
>            goto out;
> inside the "for ( i = 0; i < sched_poll->nr_ports; i++ )" loop then this
> indicates that the event channel is pending. If you aren't seeing this
> on the guest end then there is likely a problem somewhere on that end.
>
> In your current ring_wait function you have:
>        int wait = test_and_clear_bit(event, shinfo->evtchn_pending);
>        int ret = 1;
>        while (wait!=0 || ret!=0){
>                ret = hypercall_sched_op(SCHEDOP_poll, &poll);
>                wait = test_and_clear_bit(event, shinfo->evtchn_pending);
>                struct vcpu_info *vcpu = shinfo->vcpu_info;
>                dprintf(1,"DEBUG bit clear is %d and ret %d\n",wait,ret);
>                time = shinfo->vcpu_info[0].time;
>                dprintf(1,"TIME system %d timestamp 
> %d\n",time.system_time,time.tsc_timestamp);
>        }
> }
>
> Isn't "wait!=0" backwards? Don't you want to succeed (i.e. fall out of
> the loop) when wait!=0 rather than keep looping?

Yes, at some point I must have screwed that up, and later corrected
it... Sorry... Yet the problem remains, in the ring wait I get
stuck...

What else could I check?

>
> Ian.
>
>>
>> Thanks all,
>>
>> Daniel
>> >
>> > Ian.
>> >
>> >>
>> >> >
>> >> > --
>> >> > Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
>> >> > T: +44 (0)1223 225 900, http://www.citrix.com
>> >> >
>> >> >
>> >> > _______________________________________________
>> >> > Xen-devel mailing list
>> >> > Xen-devel@xxxxxxxxxxxxxxxxxxx
>> >> > http://lists.xensource.com/xen-devel
>> >> >
>> >>
>> >>
>> >>
>> >
>> >
>> >
>>
>>
>>
>
>
>



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

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