linux-kernel - Re: [PATCH -next] tracepoint: ipi: don't trace IPI on offline CPUs

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Message-ID: <56E051F0.9030800@arm.com>
Date:	Wed, 9 Mar 2016 16:40:16 +0000
From:	Sudeep Holla <sudeep.holla@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Sudeep Holla <sudeep.holla@....com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH -next] tracepoint: ipi: don't trace IPI on offline CPUs



On 09/03/16 16:05, Steven Rostedt wrote:
> On Wed,  9 Mar 2016 12:22:22 +0000
> Sudeep Holla <sudeep.holla@....com> wrote:
>
>
>> Hi Steven,
>>
>> I observed that in "include/linux/tracepoint.h", we have
>> #define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)
>> ...
>>                   if (!cpu_online(raw_smp_processor_id()))
>>                           return;
>>
>>                   if (!(cond))
>>                           return;
>> ...
>>
>> where !cond check seems reduntant if it's cpu_online check.
>> So, does this patch handle the warning correctly or is there any better
>> way ? I did see few traces with same condition, just thought of checking
>> with you.
>>
>
> Bah, I forgot that we have lockdep checks for when the event isn't
> enabled.

Yes I was about to ask you the same. I did further digging to check if I
was missing something after seeing your series[1] especially patch 2/12
(tracing: Remove duplicate checks for online CPUs)

> Can you try this patch:

It works. Thanks for the quick fix.

Tested-by: Sudeep Holla <sudeep.holla@....com>

--
Regards,
Sudeep

[1] http://www.spinics.net/lists/kernel/msg2208604.html