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Re: [Qemu-devel] [PATCH] trace: disallow more than 10 arguments per trac
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] trace: disallow more than 10 arguments per trace event |
Date: |
Wed, 3 May 2017 14:53:39 +0100 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Wed, Apr 26, 2017 at 04:39:00PM +0100, Daniel P. Berrange wrote:
> The UST trace backend can only cope with upto 10 arguments. To ensure we
> don't exceed the limit when UST is not compiled in, disallow more than
> 10 arguments upfront.
>
> This prevents the case where:
>
> commit 0fc8aec7de64f2bf83a274a2a38b938ce03425d2
> Author: Zhang Chen <address@hidden>
> Date: Tue Apr 18 10:20:20 2017 +0800
>
> COLO-compare: Optimize tcp compare trace event
>
> Optimize two trace events as one, adjust print format make
> it easy to read. rename trace_colo_compare_pkt_info_src/dst
> to trace_colo_compare_tcp_info.
>
> regressed the fix done in
>
> commit 2dfe5113b11ce0ddb08176ebb54ab7ac4104b413
> Author: Alex Bennée <address@hidden>
> Date: Fri Oct 28 14:25:59 2016 +0100
>
> net: split colo_compare_pkt_info into two trace events
>
> It seems there is a limit to the number of arguments a UST trace event
> can take and at 11 the previous trace command broke the build. Split the
> trace into a src pkt and dst pkt trace to fix this.
>
> Signed-off-by: Alex Bennée <address@hidden>
> Message-id: address@hidden
> Reviewed-by: Peter Maydell <address@hidden>
> Signed-off-by: Peter Maydell <address@hidden>
>
> 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
>
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
>
> Obviously dont apply this until 0fc8aec7de64f2bf83a274a2a38b938ce03425d2 has
> been reverted :-)
>
> scripts/tracetool/__init__.py | 4 ++++
> 1 file changed, 4 insertions(+)
Thanks, applied to my tracing tree:
https://github.com/stefanha/qemu/commits/tracing
Stefan
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Stefan Hajnoczi <=