Re: [PATCH 2/4] ARM: add IPI tracepoints

From: Nicolas Pitre
Date: Fri Jul 18 2014 - 22:55:22 EST


On Fri, 18 Jul 2014, Steven Rostedt wrote:

> On Fri, 18 Jul 2014 16:55:42 -0400 (EDT)
> Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> wrote:
>
> >
> > Here's the patch I have at the head of the series now, with the above
> > ugliness changed to an unconditional __tracepoint_string attribute.
> >
>
> I was thinking of something like this. Feel free to add this to your
> series.

OK. Same end result, but much clearer. Thanks.

Any comments / ACKs on the other patches? I'd like to see 1/4 to 3/4
(and your patch) merged upstream during the next window. 4/4 is up for
debate.

> -- Steve
>
> From: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Subject: [PATCH] tracing: Do not do anything special with tracepoint_string when tracing is disabled
>
> When CONFIG_TRACING is not enabled, there's no reason to save the trace
> strings either by the linker or as a static variable that can be
> referenced later. Simply pass back the string that is given to
> tracepoint_string().
>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> ---
> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
> index cff3106..b296363 100644
> --- a/include/linux/ftrace_event.h
> +++ b/include/linux/ftrace_event.h
> @@ -574,6 +574,7 @@ do { \
> __trace_printk(ip, fmt, ##args); \
> } while (0)
>
> +#ifdef CONFIG_TRACING
> /**
> * tracepoint_string - register constant persistent string to trace system
> * @str - a constant persistent string that will be referenced in tracepoints
> @@ -607,6 +608,15 @@ do { \
> ___tp_str; \
> })
> #define __tracepoint_string __attribute__((section("__tracepoint_str")))
> +#else
> +/*
> + * tracepoint_string() is used to save the string address for userspace
> + * tracing tools. When tracing isn't configured, there's no need to save
> + * anything.
> + */
> +# define tracepoint_string(str) str
> +# define __tracepoint_string
> +#endif
>
> #ifdef CONFIG_PERF_EVENTS
> struct perf_event;
>
>
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