Re: [Xen-devel] Debug event_channel.c

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

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?

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
> >> >
> >>
> >>
> >>
> >
> >
> >
> 
> 
> 



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