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SubjectRe: [PATCH] markers: let marker_debug as module parameter

* Lai Jiangshan <laijs@cn.fujitsu.com> wrote:

> if we want to enable marker debug output, we have to modify
> the code and remake/reinstall the kernel in current code.
>
> this patch enable marker_debug to be set when kernel start.
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/kernel/marker.c b/kernel/marker.c
> index 9f76c4a..5d8404f 100644
> --- a/kernel/marker.c
> +++ b/kernel/marker.c
> @@ -28,8 +28,9 @@
> extern struct marker __start___markers[];
> extern struct marker __stop___markers[];
>
> -/* Set to 1 to enable marker debug output */
> -static const int marker_debug;
> +static int marker_debug;
> +module_param(marker_debug, bool, 0);
> +MODULE_PARM_DESC(marker_debug, "Set to 1 to enable marker debug output");

hm, in tip/master we already have ftrace_printk(), which allows such
debug output to any of the active tracers. That is a far more useful way
of debugging such things. See:

http://people.redhat.com/mingo/tip.git/README

and:

http://redhat.com/~mingo/sched-devel.git/readme-tracer.txt

note how much cleaner and more usable it will also become: no silly
module flags or recompilation to activate this debug output, and no
debug clutter in the syslog.

if you enable tracing in the 'nop' tracer then only the
ftrace_printk()'s will be printed, no other trace entries.

Ingo


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