Re: [Qemu-devel] [PATCH] trace: disallow more than 10 arguments per trace event

[Eric Blake <eblake@redhat.com>]

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On 04/26/2017 10:39 AM, Daniel P. Berrange wrote:
> The UST trace backend can only cope with upto 10 arguments. To ensure we

s/upto/up to/

> don't exceed the limit when UST is not compiled in, disallow more than
> 10 arguments upfront.
> 
> This prevents the case where:
> 
>   commit 0fc8aec7de64f2bf83a274a2a38b938ce03425d2

> 
> regressed the fix done in
> 
>   commit 2dfe5113b11ce0ddb08176ebb54ab7ac4104b413

> 
> Now we get an immediate fail even when UST is disabled:
> 
>   GEN     net/trace.h
> Traceback (most recent call last):
>   File "/home/berrange/src/virt/qemu/scripts/tracetool.py", line 154, in <module>
>     main(sys.argv)
>   File "/home/berrange/src/virt/qemu/scripts/tracetool.py", line 145, in main
>     events.extend(tracetool.read_events(fh))
>   File "/home/berrange/src/virt/qemu/scripts/tracetool/__init__.py", line 307, in read_events
>     event = Event.build(line)
>   File "/home/berrange/src/virt/qemu/scripts/tracetool/__init__.py", line 244, in build
>     event = Event(name, props, fmt, args)
>   File "/home/berrange/src/virt/qemu/scripts/tracetool/__init__.py", line 196, in __init__
>     "argument count" % name)
> ValueError: Event 'colo_compare_tcp_info' has more than maximum permitted argument count
> Makefile:96: recipe for target 'net/trace.h-timestamp' failed

Not necessarily the nicest-looking error, but sufficient to prevent the
regression.

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> 
> Obviously dont apply this until 0fc8aec7de64f2bf83a274a2a38b938ce03425d2 has
> been reverted :-)

It now has: commit 51b9d495.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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