linux-kernel - Re: [PATCH resend] tracing/events: convert NAPI's tracepoint via TRACE

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Date:	Mon, 31 Aug 2009 21:41:06 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, David Miller <davem@...emloft.net>,
	Neil Horman <nhorman@...driver.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Wei Yongjun <yjwei@...fujitsu.com>,
	Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH resend] tracing/events: convert NAPI's tracepoint via
 TRACE_EVENT

On Tue, 2009-09-01 at 09:06 +0800, Xiao Guangrong wrote:
> 
> Steven Rostedt wrote:
> > On Mon, 31 Aug 2009, Xiao Guangrong wrote:
> > 
> >> - Convert NAPI's tracepoint via TRACE_EVENT macro, the output information
> >>   like below:
> >>
> >>    sshd-2503  [000]    71.920846: napi_poll: ifname=eth0 state=0 weigth=16 poll=pcnet32_poll
> >>    sshd-2503  [000]    72.020291: napi_poll: ifname=eth0 state=0 weigth=16 poll=pcnet32_poll
> >>    sshd-2503  [000]    72.020418: napi_poll: ifname=eth0 state=NAPI_STATE_SCHED weigth=16 poll=pcnet32_poll
> >>
> >> - Remove the "DECLARE_TRACE" definiens in include/trace/define_trace.h,
> >>   because TRACE_EVENT not use it
> > 
> > The above really needs to be in a separate patch, since it is a tracing 
> > infrastructure change.
> > 
> 
> Hi Steven,
> 
> We can't break this patch into two patches, because it's has redefined 'DECLARE_TRACE'
> in include/trace/define_trace.h, like below:
> 
> 1: if we remove 'DECLARE_TRACE' first, then NAPI's tracepoint can't define tracepoint
>    (it's a NAPI tracepoint's bug,
>     see my previous patch: http://marc.info/?l=linux-kernel&m=125118032931716&w=2)
> 
> 2: if we convert NAPI's tracepoint first, it can't include more TRACE_EVENT .h files in
>    one .c file, the compiler will complain with variables redefined:
> 
> include/trace/events/napi.h:15: error: redefinition of ‘__tpstrtab_napi_poll’
> include/trace/events/napi.h:15: error: previous definition of ‘__tpstrtab_napi_poll’ was here
> include/trace/events/napi.h:15: error: redefinition of ‘__tracepoint_napi_poll’
> include/trace/events/napi.h:15: error: previous definition of ‘__tracepoint_napi_poll’ was here
> In file included from include/trace/ftrace.h:644,
> 
> So, I think we do better fix this bug early, then other people can go on his work on ftrace.

Ah, I missed the dependency there. That needs to be commented in the
change log. That is, to comment that a dependency exists.

Luckily, none of the DECLARE_TRACE users used the CREATE_TRACEPOINT way
of creating the trace points. Of course using DECLARE_TRACE directly is
now deprecated, but this change would have broken it if it was used,
because the define_trace.h was also written for that in mind. But since
we never converted any of the old users to do so, this wont break
anything.

OK, you have have Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve


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