[PATCH] ftrace: Consistently restore trace function on sysctl enabling

[PATCH] ftrace: Consistently restore trace function on sysctl enabling

[Jan Kiszka]

If we reenable ftrace via syctl, we currently set ftrace_trace_function
based on the previous simplistic algorithm. This is inconsistent with
what update_ftrace_function does. So better call that helper instead.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 kernel/trace/ftrace.c |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 62b71f6..b9b90f0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4538,12 +4538,8 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 		ftrace_startup_sysctl();
 
 		/* we are starting ftrace again */
-		if (ftrace_ops_list != &ftrace_list_end) {
-			if (ftrace_ops_list->next == &ftrace_list_end)
-				ftrace_trace_function = ftrace_ops_list->func;
-			else
-				ftrace_trace_function = ftrace_ops_list_func;
-		}
+		if (ftrace_ops_list != &ftrace_list_end)
+			update_ftrace_function();
 
 	} else {
 		/* stopping ftrace calls (just send to ftrace_stub) */
-- 
1.7.3.4

Re: [PATCH] ftrace: Consistently restore trace function on sysctl enabling

[Steven Rostedt]

On Tue, 2013-03-26 at 17:53 +0100, Jan Kiszka wrote:
> If we reenable ftrace via syctl, we currently set ftrace_trace_function
> based on the previous simplistic algorithm. This is inconsistent with
> what update_ftrace_function does. So better call that helper instead.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  kernel/trace/ftrace.c |    8 ++------
>  1 files changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 62b71f6..b9b90f0 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4538,12 +4538,8 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
>  		ftrace_startup_sysctl();
>  
>  		/* we are starting ftrace again */
> -		if (ftrace_ops_list != &ftrace_list_end) {
> -			if (ftrace_ops_list->next == &ftrace_list_end)
> -				ftrace_trace_function = ftrace_ops_list->func;
> -			else
> -				ftrace_trace_function = ftrace_ops_list_func;
> -		}

I remember there was a reason why I didn't update this, but I can't
remember why. Looking at it now, it doesn't look like there is a reason.

I'll have to think about this one more. Another score for not
commenting :-p

Thanks,

-- Steve

> +		if (ftrace_ops_list != &ftrace_list_end)
> +			update_ftrace_function();
>  
>  	} else {
>  		/* stopping ftrace calls (just send to ftrace_stub) */

Re: [PATCH] ftrace: Consistently restore trace function on sysctl enabling

[Steven Rostedt]

On Tue, 2013-03-26 at 15:10 -0400, Steven Rostedt wrote:

> I remember there was a reason why I didn't update this, but I can't
> remember why. Looking at it now, it doesn't look like there is a reason.

I remember now. I didn't add it because the update_ftrace_function was
too much at the time. It was still doing the basic updates, but it was
also doing a bit more too. But this was before I added the extra checks.
I didn't call it because it seemed to be an overkill. But that doesn't
apply today.


> 
> I'll have to think about this one more. Another score for not
> commenting :-p

OK, I'll add it and it looks like it needs to go immediately, as well as
way back to 3.0 stable.

Thanks!

-- Steve