Re: [PATCH 02/13] tracing: Extract calls to trace_define_common_fields()

[Lai Jiangshan]

Li Zefan wrote:
> Call trace_define_common_fields() in event_create_dir() only.
> 
>    text    data     bss     dec     hex filename
> 5346802 1961864 7103260 14411926         dbe896 vmlinux.o.old
> 5345151 1961864 7103260 14410275         dbe223 vmlinux.o
> 
> Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
> Acked-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>

I think this is a urgent patch for mainline.

I have found a regression at trace_kprobe, and I'm lucky to find that this
patch can also fix this regression.


> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1113,10 +1113,6 @@ static int kprobe_event_define_fields(struct ftrace_event_call *event_call)
>  	struct kprobe_trace_entry field;
>  	struct trace_probe *tp = (struct trace_probe *)event_call->data;
>  
> -	ret = trace_define_common_fields(event_call);
> -	if (!ret)
> -		return ret;
> -
>  	DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
>  	DEFINE_FIELD(int, nargs, FIELD_STRING_NARGS, 1);
>  	/* Set argument names as fields */
> @@ -1131,10 +1127,6 @@ static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
>  	struct kretprobe_trace_entry field;
>  	struct trace_probe *tp = (struct trace_probe *)event_call->data;
>  
> -	ret = trace_define_common_fields(event_call);
> -	if (!ret)
> -		return ret;
> -
>  	DEFINE_FIELD(unsigned long, func, FIELD_STRING_FUNC, 0);
>  	DEFINE_FIELD(unsigned long, ret_ip, FIELD_STRING_RETIP, 0);
>  	DEFINE_FIELD(int, nargs, FIELD_STRING_NARGS, 1);

"if (!ret)" is wrong. trace_define_common_fields() returns zero when success.
So "unsigned long, func", "unsigned long, ret_ip" ...etc are NOT "defined"
and filters can not be applied for trace_kprobe.

Reviewed-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>

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