linux-kernel - Re: [PATCH v9 1/1] Tracepoint: register/unregister struct tracepoint

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Date:	Fri, 4 Apr 2014 13:19:10 +0000 (UTC)
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH v9 1/1] Tracepoint: register/unregister struct
 tracepoint

----- Original Message -----
> From: "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>
> To: "Steven Rostedt" <rostedt@...dmis.org>
> Cc: linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...nel.org>, "Frederic Weisbecker" <fweisbec@...il.com>,
> "Andrew Morton" <akpm@...ux-foundation.org>, "Frank Ch. Eigler" <fche@...hat.com>, "Johannes Berg"
> <johannes.berg@...el.com>
> Sent: Thursday, April 3, 2014 11:40:17 PM
> Subject: Re: [PATCH v9 1/1] Tracepoint: register/unregister struct tracepoint
> 
> ----- Original Message -----
> > From: "Steven Rostedt" <rostedt@...dmis.org>
> > To: "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>
> > Cc: linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...nel.org>,
> > "Frederic Weisbecker" <fweisbec@...il.com>,
> > "Andrew Morton" <akpm@...ux-foundation.org>, "Frank Ch. Eigler"
> > <fche@...hat.com>, "Johannes Berg"
> > <johannes.berg@...el.com>
> > Sent: Thursday, April 3, 2014 2:54:41 PM
> > Subject: Re: [PATCH v9 1/1] Tracepoint: register/unregister struct
> > tracepoint
> > 
> > On Thu, 3 Apr 2014 17:49:54 +0000 (UTC)
> > Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> > 
> > 
> > > So my current thinking is that the pre-existing code was erroneously
> > > enabling tracepoints with the name of every event enabled (including
> > > e.g. function tracer, kprobes, etc). It was not failing because
> > > tracepoint.c silently accepted to enable tracepoints were not loaded
> > > yet.
> > > 
> > 
> > If that was true, than wouldn't the error code I added have returned an
> > error?
> 
> Good point.
> 
> I found the culprit:
> 
> [    0.560002] event_trace_enable: �GT����� call ffffffff81613930 (core)
> [    0.564001] event_trace_enable: �GTȁ���� call ffffffff816139c0 (core)
> 
> compudj@ok:~/git/rostedt/linux-trace$ objdump -t vmlinux |grep
> ffffffff81613930
> ffffffff81613930 l     O .data	0000000000000090 event_sys_exit
> compudj@ok:~/git/rostedt/linux-trace$ objdump -t vmlinux |grep
> ffffffff816139c0
> ffffffff816139c0 l     O .data	0000000000000090 event_sys_enter
> 
> I'll look into those two sites tomorrow morning.

And here is the fix:

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 7538389..75e64e8 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -371,7 +371,7 @@ struct ftrace_event_file {
 #define __TRACE_EVENT_FLAGS(name, value)                               \
        static int __init trace_init_flags_##name(void)                 \
        {                                                               \
-               event_##name.flags = value;                             \
+               event_##name.flags |= value;                            \
                return 0;                                               \
        }                                                               \
        early_initcall(trace_init_flags_##name);

I will respin a new version after some extra testing.

Thanks!

Mathieu


> 
> Thanks,
> 
> Mathieu
> 
> > 
> > -- Steve
> > 
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
--
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