Re: [Qemu-devel] [PATCH] net: split colo_compare_pkt_info into two trace events

[Eric Blake]

On 10/31/2016 06:42 AM, Alex Bennée wrote:
> 
> Zhang Chen <address@hidden> writes:
>> It looks good for me, but it not the root cause of this bug.
>> We better fix this in UST trace event codes....
> 
> I didn't get a chance to dig into the details but yes we need to confirm
> if this is a limitation with UST or just the macro headers we generate
> for it. That said this is the first time I think we have exceeded 10
> parameters for a trace event.

Not the first time; see commit defbaec back in June.

The limit appears to be inherent in UST:

    For more information see comment regarding TP_ARGS
    in lttng/tracepoint.h:

    /*
    * TP_ARGS takes tuples of type, argument separated by a comma.
    * It can take up to 10 tuples (which means that less than 10 tuples is
    * fine too).
    * Each tuple is also separated by a comma.
    */

But I agree that fixing the trace generation code to hard-fail on 11
arguments even when UST is not the active trace engine would be a nice
service to developers.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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