linux-kernel - Re: [PATCH 6/6] uprobes/perf: Always increment trace

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Message-ID: <20130204111711.GB12900@linux.vnet.ibm.com>
Date:	Mon, 4 Feb 2013 16:47:11 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Anton Arapov <anton@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Josh Stone <jistone@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"Suzuki K. Poulose" <suzuki@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] uprobes/perf: Always increment trace_uprobe->nhit

* Oleg Nesterov <oleg@...hat.com> [2013-01-31 20:18:32]:

> Move tu->nhit++ from uprobe_trace_func() to uprobe_dispatcher().
> 
> ->nhit counts how many time we hit the breakpoint inserted by this
> uprobe, we do not want to loose this info if uprobe was enabled by
> sys_perf_event_open().
> 

Though I dont see a problem with this change, It seems unnecessary for
me.

Info from nhits is mostly for /sys/kernel/debug/tracing/uprobe_profile

I am not sure how sys_perf_event_open() is making use of this?

> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/trace/trace_uprobe.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 55cdc14..0a9a8de 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -473,8 +473,6 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
>  	unsigned long irq_flags;
>  	struct ftrace_event_call *call = &tu->call;
> 
> -	tu->nhit++;
> -
>  	local_save_flags(irq_flags);
>  	pc = preempt_count();
> 
> @@ -698,6 +696,7 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
>  	struct trace_uprobe *tu;
> 
>  	tu = container_of(con, struct trace_uprobe, consumer);
> +	tu->nhit++;
> 
>  	if (tu->flags & TP_FLAG_TRACE)
>  		uprobe_trace_func(tu, regs);
> -- 
> 1.5.5.1
> 

-- 
Thanks and Regards
Srikar Dronamraju

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