Re: How to recheck 'maxactive' ?

On Mon, 23 Mar 2020 15:47:41 +0900
Masami Hiramatsu <[email protected]> wrote:

> Hi Taeung,
> 
> On Sun, 22 Mar 2020 23:06:20 +0900
> Taeung Song <[email protected]> wrote:
> 
> > Hi,
> > 
> > After setting 'maxactive' for kretprobe,
> > how can I recheck the value of 'maxactive' ?
> > For example, in order to distinguish the difference
> > between two kretprobe events
> > (kmem_cache_alloc_node and kmem_cache_alloc_node10)
> > 
> >    $ cd /sys/kernel/debug/tracing
> >    $ echo 'r:kmem_cache_alloc_node kmem_cache_alloc_node' >> kprobe_events
> >    $ echo 'r10:kmem_cache_alloc_node10 kmem_cache_alloc_node' >> 
> > kprobe_events
> > 
> >    $ cat kprobe_events
> >    r:kprobes/kmem_cache_alloc_node kmem_cache_alloc_node
> >    r:kprobes/kmem_cache_alloc_node10 kmem_cache_alloc_node  
> 
> Oops! good catch. That must be a bug, since the kprobe_events design policy
> is to support following operation.
> 
> $ cat kprobe_events > /etc/event_setting
> (reboot)
> $ cat /etc/event_setting > kprobe_events
> 
> What about below patch?
> 
> >From 935ed56819f2bfb7ac977f5c63273c9a6e3dfb42 Mon Sep 17 00:00:00 2001  
> From: Masami Hiramatsu <[email protected]>
> Date: Mon, 23 Mar 2020 10:57:48 +0900
> Subject: [PATCH] ftrace/kprobe: Show the maxactive number on kprobe_events
> 
> Show maxactive parameter on kprobe_events.
> This allows user to save the current configuration and
> restore it without losing maxactive parameter.
> 

Hi Masami,

Can you resend this patch as a stand alone (so that it shows up as a patch
on the mailing lists).

Thanks!

-- Steve


> Signed-off-by: Masami Hiramatsu <[email protected]>
> ---
>  kernel/trace/trace_kprobe.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 362cca52f5de..d0568af4a0ef 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1078,6 +1078,8 @@ static int trace_kprobe_show(struct seq_file *m, struct dyn_event *ev)
>  	int i;
>  
>  	seq_putc(m, trace_kprobe_is_return(tk) ? 'r' : 'p');
> +	if (trace_kprobe_is_return(tk) && tk->rp.maxactive)
> +		seq_printf(m, "%d", tk->rp.maxactive);
>  	seq_printf(m, ":%s/%s", trace_probe_group_name(&tk->tp),
>  				trace_probe_name(&tk->tp));
>