linux-kernel - Re: [PATCH 0/3] tracing/function-graph-tracer: signal interrupt triggering on output

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Date:	Sat, 13 Dec 2008 08:49:32 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frédéric Weisbecker <fweisbec@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] tracing/function-graph-tracer: signal interrupt
	triggering on output


* Frédéric Weisbecker <fweisbec@...il.com> wrote:

> > applied to tip/tracing/function-graph-tracer, thanks Frederic!
> >
> > The output looks really nice.
> >
> >        Ingo
> >
> 
> Thanks :-)
> 
> If anyone  has other needs or suggestions about this tracer, don't
> hesitate to request it.
> I remember Peter suggested that the preempt count could be output.

that reminds me ... did you know about hardirq_count()? We could use it 
to detect IRQ entries in a more generic way, instead of the section 
trick?

Another thing, i just noticed that ftrace_print() is broken in certain 
situations, for example a plain newline:

        ftrace_printk("\n");

printed via trace_pipe will print some weirdly concatenated line:

           <...>-2994  [007]   406.498986: debug_show:          <...>-2994  [007]   406.498986:            <...>-2994  [007]   406.498986: debug_show: 

not via a separate, standalone, empty line.

Another thing: it would be nice to have a trace_option to leave out this 
preamble:

           <...>-2994  [007]   406.498986: debug_show:  test printk

and just give this output:

 test printk

i.e. some 'printk compatibility' mode. That way i could use 
ftrace_printk() as a pure replacement for printk, during development.

	Ingo
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