linux-kernel - Re: [PATCH] kernel: trace: remove __init from race_selftest_startup_function() and trace_selftest_startup_function

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Date:	Thu, 11 Jul 2013 22:38:55 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel: trace: remove __init from
 race_selftest_startup_function() and trace_selftest_startup_function_graph()

On Fri, 2013-07-12 at 09:58 +0800, Chen Gang wrote:
> On 07/12/2013 09:41 AM, Steven Rostedt wrote:
> > On Fri, 2013-07-12 at 07:51 +0800, Chen Gang wrote:
> > 
> >> > Hmm, can all trace_selftest_startup_* (*selftest* in trace_selftest.c)
> >> > use '__init', so not waste memory keeping them around ?
> > Yeah, they should all be set to __init, but that's pretty low on the
> > totem poll, as distros don't enable selftests in their main kernels.
> 
> Excuse me, my English is not quite well, I guess your meaning is:
> 
>   they should all be set to '__init', although it is minor in real world.
> 
> Is it correct ?

Correct.

> 
> 
> For me, I recommend to let all *selftest* as the same: "all add '
> __init' or none add '__init'" (if choose add, all report warnings).
> 
> Is it suitable to still send new related patch for it ? If so, could
> you provide your suggesting choice (all add, or none add) ?

Does this patch fix your warning?

-- Steve

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index a4ed382..5e794d1 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -680,6 +680,15 @@ extern int trace_selftest_startup_sched_switch(struct tracer *trace,
 					       struct trace_array *tr);
 extern int trace_selftest_startup_branch(struct tracer *trace,
 					 struct trace_array *tr);
+/*
+ * Tracer data references selftest functions that only occur
+ * on boot up. These can be __init functions. Thus, when selftests
+ * are enabled, then the tracers need to reference __init functions.
+ */
+#define __tracer_data		__refdata
+#else
+/* Tracers are seldom changed. Optimize when selftests are disabled. */
+#define __tracer_data		__read_mostly
 #endif /* CONFIG_FTRACE_STARTUP_TEST */
 
 extern void *head_page(struct trace_array_cpu *data);
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index b863f93..38fe148 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -199,7 +199,7 @@ static int func_set_flag(u32 old_flags, u32 bit, int set)
 	return 0;
 }
 
-static struct tracer function_trace __read_mostly =
+static struct tracer function_trace __tracer_data =
 {
 	.name		= "function",
 	.init		= function_trace_init,


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