2017-08-11 11:31:56

by Pratyush Anand

Subject: [PATCH] tracer: hwlat: allow to be default bootup tracer

hwlat is not a production kernel tracer, however it can be used to
identify any HW latency issue during kernel boot as well.Therefore call
init_hwlat_tracer() though core_initcall() so that we can pass
ftrace=hwlat in kernel commandline parameter and we can have hwlat as
default bootup tracer.

Signed-off-by: Pratyush Anand <[email protected]>
---
kernel/trace/trace_hwlat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index d7c8e4ec3d9d..09f8f0950b6c 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -630,4 +630,4 @@ __init static int init_hwlat_tracer(void)

return 0;
}
-late_initcall(init_hwlat_tracer);
+core_initcall(init_hwlat_tracer);
--
2.9.4

2017-08-16 14:28:06

by Steven Rostedt

Subject: Re: [PATCH] tracer: hwlat: allow to be default bootup tracer

On Fri, 11 Aug 2017 17:01:21 +0530
Pratyush Anand <[email protected]> wrote:

> hwlat is not a production kernel tracer, however it can be used to
> identify any HW latency issue during kernel boot as well.Therefore call
> init_hwlat_tracer() though core_initcall() so that we can pass
> ftrace=hwlat in kernel commandline parameter and we can have hwlat as
> default bootup tracer.
>
> Signed-off-by: Pratyush Anand <[email protected]>
> ---
> kernel/trace/trace_hwlat.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> index d7c8e4ec3d9d..09f8f0950b6c 100644
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -630,4 +630,4 @@ __init static int init_hwlat_tracer(void)
>
> return 0;
> }
> -late_initcall(init_hwlat_tracer);
> +core_initcall(init_hwlat_tracer);

No that is not the right fix. hwlat tracer should not be called by core
init.

I already have a fix in linux-next. I'm doing some more code that needs
testing before I send it to Linus.

-- Steve