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SubjectRe: [PATCH] tracing: fix incorrect enabling of trace events by boot cmdline
On Thu, 16 Apr 2015 13:44:44 +0900
Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:

> There is a problem that trace events are not properly enabled with
> boot cmdline. Problem is that if we pass "trace_event=kmem:mm_page_alloc"
> to boot cmdline, it enables all kmem trace events.
>
> It is caused by parsing mechanism. When we parse cmdline, buffer
> contents is modified due to tokenization. And, if we use this buffer
> again, we will get wrong result.
>
> Unfortunately, this buffer should be accessed three times
> to set trace events properly in boot time. So, we need to handle
> this situation.
>
> There is already handling code for ",", but, we need another for
> ":". This patch add it.

Thanks, but your patch has a bug in it. I'll fix it up.

>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> ---
> kernel/trace/trace_events.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index db54dda..ce5b194 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -565,6 +565,7 @@ static int __ftrace_set_clr_event(struct trace_array *tr, const char *match,
> static int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
> {
> char *event = NULL, *sub = NULL, *match;
> + int ret;
>
> /*
> * The buf format can be <subsystem>:<event-name>
> @@ -590,7 +591,11 @@ static int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
> event = NULL;
> }
>
> - return __ftrace_set_clr_event(tr, match, sub, event, set);
> + ret = __ftrace_set_clr_event(tr, match, sub, event, set);
> +
> + /* Put back the colon to allow this to be called again */
> + if (buf)
> + *(buf - 1) = ':';

You forgot to add:

return ret;

-- Steve

> }
>
> /**



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