linux-kernel - Re: [PATCH 2/2] tracing/rcu: don't trace rcu

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Date:	Sun, 14 Feb 2016 20:35:43 +0300
From:	Denis Kirjanov <kda@...ux-powerpc.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs

On 2/14/16, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Sat, 13 Feb 2016 21:22:53 +0300
> Denis Kirjanov <kda@...ux-powerpc.org> wrote:
>
>>
>> diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
>> index ef72c4a..5470f2f 100644
>> --- a/include/trace/events/rcu.h
>> +++ b/include/trace/events/rcu.h
>> @@ -435,6 +435,8 @@ TRACE_EVENT(rcu_callback,
>>
>>  	TP_ARGS(rcuname, rhp, qlen_lazy, qlen),
>>
>> +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
>> +
>
> Besides the fact that this isn't a TRACE_EVENT_CONDITION, Isn't calling
> rcu_callback() dangerous from an offline CPU?

That was the wrong patch, I've sent the v2.

>
> Or is calling a callback from an offline CPU OK?
>
> Perhaps it is OK, as it doesn't need to worry about its current CPU,
> just the other CPUs.
>
> Paul?
>
> -- Steve
>
>
>>  	TP_STRUCT__entry(
>>  		__field(const char *, rcuname)
>>  		__field(void *, rhp)
>
>