linux-kernel - Re: [PATCH v3 2/3] tracing: Add trace

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Date:   Tue, 30 Aug 2016 16:20:52 +0200
From:   Daniel Wagner <daniel.wagner@...-carit.de>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Binoy Jayan <binoy.jayan@...aro.org>
CC:     Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        <linaro-kernel@...ts.linaro.org>, Carsten Emde <C.Emde@...dl.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        Masami <masami.hiramatsu@...aro.org>
Subject: Re: [PATCH v3 2/3] tracing: Add trace_irqsoff tracepoints

On 08/30/2016 04:01 PM, Daniel Wagner wrote:
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 03c0a48..ab8958f 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -152,7 +152,8 @@ EXPORT_SYMBOL_GPL(trace_define_field);
>  
>  #define __generic_field(type, item, filter_type)			\
>  	ret = __trace_define_field(&ftrace_generic_fields, #type,	\
> -				   #item, 0, 0, is_signed_type(type),	\
> +				   #item, 0, sizeof(type),		\
> +				   is_signed_type(type),		\
>  				   filter_type);			\
>  	if (ret)							\
>  		return ret;
> 
> 
> After that I get this funky report (with only 4 cpus):

Just setting the size of the type is not enough. The hist_field_* 
getter function want to know the offset too:


#define DEFINE_HIST_FIELD_FN(type)					\
static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
{									\
	type *addr = (type *)(event + hist_field->field->offset);	\
									\
	return (u64)(unsigned long)*addr;				\
}

The problem we have here is that there is no cpu field in the event
record.