linux-kernel - Re: [PATCH 3/4] tracing/uprobes: Kill the bogus UPROBE_HANDLER_REMOVE code in uprobe

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Date:	Mon, 30 Jun 2014 15:03:29 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	"zhangwei\(Jovi\)" <jovi.zhangwei@...wei.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] tracing/uprobes: Kill the bogus UPROBE_HANDLER_REMOVE code in uprobe_dispatcher()

On Fri, 27 Jun 2014 19:01:43 +0200, Oleg Nesterov wrote:
> I do not know why dd9fa555d7bb "tracing/uprobes: Move argument fetching
> to uprobe_dispatcher()" added the UPROBE_HANDLER_REMOVE, but it looks
> wrong.
>
> OK, perhaps it makes sense to avoid store_trace_args() if the tracee is
> nacked by uprobe_perf_filter(). But then we should kill the same code
> in uprobe_perf_func() and unify the TRACE/PROFILE filtering (we need to
> do this anyway to mix perf/ftrace). Until then this code actually adds
> the pessimization because uprobe_perf_filter() will be called twice and
> return T in likely case.

Right, I wanted to avoid to call the store_trace_args() which might be
costly if possible.  But it seems not necessary since it doesn't get
called once handler returns UPROBE_HANDLER_REMOVE.  And we need to fix
the filtering first..

So I'm okay with removing this "pessimization". :)

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/trace/trace_uprobe.c |    6 ------
>  1 files changed, 0 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 08e7970..c4cf0ab 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -1208,12 +1208,6 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
>  
>  	current->utask->vaddr = (unsigned long) &udd;
>  
> -#ifdef CONFIG_PERF_EVENTS
> -	if ((tu->tp.flags & TP_FLAG_TRACE) == 0 &&
> -	    !uprobe_perf_filter(&tu->consumer, 0, current->mm))
> -		return UPROBE_HANDLER_REMOVE;
> -#endif
> -
>  	if (WARN_ON_ONCE(!uprobe_cpu_buffer))
>  		return 0;
--
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