Re: [PATCH] trace/simple: Allow enabling simple traces from command line

[Markus Armbruster]

Josh DuBois <josh@joshdubois.com> writes:

> Well, this is a bit embarrassing.  The patch below simply
> re-introduced the bug which the Fixes: line was trying to fix in the
> first place.
>
> I.e, :
>
> - with my patch (just committed as
> 1b7157be3a8c4300fc8044d40f4b2e64a152a1b4) applied, a QEMU built with
> simple tracing will always produce a trace-<pid> file, regardless of
> whether traces were asked for.
>
> - after db25d56c014aa1a96319c663e0a60346a223b31e, which my patch was
> supposed to "fix," QEMU will not produce a trace file unless asked, I
> believe, via the monitor.  Enabling traces is, near as I can tell,
> simply impossible via the command-line in that case.
>
> - prior to db25d56c014aa1a96319c663e0a60346a223b31e, just like today,
> QEMU built with simple tracing will always produce a trace-<pid> file,
> regardless of whether the user asks for traces at runtime.

When you send a patch with a Fixes: tag, consider cc'ing people involved
in the commit being fixed.  I might have spotted the regression.

> I'm sorry for the mess.  Having stepped in it already, I'm  open to
> trying to track it down and fix it properly.  I imagine perhaps few
> people truly care, since traces require a special build and are
> probably only being done by developers anyway.  (And the original
> message for db25d56c014aa1a96319c663e0a60346a223b31e said it had been
> "broken" for an unknown period of time).
>
> I'm brand new around here so I'll leave it to others whether it's
> better to revert and have traces impossible to enable from the cli (as
> I say, I think they're only possible from the monitor prior to my
> "fix" ) or to leave it be.
>
> If I resubmit, I'll try to test a little more next time.  I just
> wanted my traces to work. ;)

I missed the CLI issue.  I just wanted my directories not littered with
trace files ;)

Stefan, what shall we do for 5.1?

If we keep littering, the annoyance will make me drop the trace backend
"simple" from my build tests.  I might even remember to put it back when
the fix arrives.