[PATCH][RESEND] tracing/ftrace: Remove unused code in sched_switch tracer

[PATCH][RESEND] tracing/ftrace: Remove unused code in sched_switch tracer

[Frederic Weisbecker]

When init_sched_switch_trace() is called, it has no reason to start
the sched tracer if the sched_ref is not zero.

_ If this is non-zero, the tracer is already used, but we can register it
to the tracing engine. There is already a security which avoid the tracer
probes not to be resgistered twice. 

_ If this is zero, this block will not be used.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
CC: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_sched_switch.c |    8 --------
 1 files changed, 0 insertions(+), 8 deletions(-)
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 59de514..96620c7 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -203,14 +203,6 @@ static struct tracer sched_switch_trace __read_mostly =
 
 __init static int init_sched_switch_trace(void)
 {
-	int ret = 0;
-
-	if (atomic_read(&sched_ref))
-		ret = tracing_sched_register();
-	if (ret) {
-		pr_info("error registering scheduler trace\n");
-		return ret;
-	}
 	return register_tracer(&sched_switch_trace);
 }
 device_initcall(init_sched_switch_trace);

Re: [PATCH][RESEND] tracing/ftrace: Remove unused code in sched_switch tracer

[Frédéric Weisbecker]

2008/10/31 Frederic Weisbecker <fweisbec@gmail.com>:
> When init_sched_switch_trace() is called, it has no reason to start
> the sched tracer if the sched_ref is not zero.
>
> _ If this is non-zero, the tracer is already used, but we can register it
> to the tracing engine. There is already a security which avoid the tracer
> probes not to be resgistered twice.
>
> _ If this is zero, this block will not be used.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Steven Rostedt <rostedt@goodmis.org>
> ---
>  kernel/trace/trace_sched_switch.c |    8 --------
>  1 files changed, 0 insertions(+), 8 deletions(-)
> diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
> index 59de514..96620c7 100644
> --- a/kernel/trace/trace_sched_switch.c
> +++ b/kernel/trace/trace_sched_switch.c
> @@ -203,14 +203,6 @@ static struct tracer sched_switch_trace __read_mostly =
>
>  __init static int init_sched_switch_trace(void)
>  {
> -       int ret = 0;
> -
> -       if (atomic_read(&sched_ref))
> -               ret = tracing_sched_register();
> -       if (ret) {
> -               pr_info("error registering scheduler trace\n");
> -               return ret;
> -       }
>        return register_tracer(&sched_switch_trace);
>  }
>  device_initcall(init_sched_switch_trace);
>

(depends on tracing/ftrace: Fix a race condition in sched_switch tracer)