linux-kernel - Re: [PATCH 06/13] tracing: remove dump_ran check in __ftrace

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Date:	Mon, 11 Mar 2013 10:08:14 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 06/13] tracing: remove dump_ran check in __ftrace_dump

On Mon, 2013-03-11 at 15:13 +0800, zhangwei(Jovi) wrote:
> It's reasonable to call __ftrace_dump function not only once,
> so remove the dump_ran variable checking.

This needs a little more work. On an oops, I only want it dumped once,
because a crash can cause another crash while its dumping, and without
that check in will corrupt the buffer.

Now, we have things like ctrl^z that also does a dump where we don't
want to disable it. Cleaning this up has been on my todo list for a
while. I may go ahead and clean that up myself.

-- Steve

> 
> Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@...wei.com>
> ---
>  kernel/trace/trace.c |    6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 090eddb..4cec7b8 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5106,17 +5106,12 @@ __ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode)
>  	/* use static because iter can be a bit big for the stack */
>  	static struct trace_iterator iter;
>  	unsigned int old_userobj;
> -	static int dump_ran;
>  	unsigned long flags;
>  	int cnt = 0, cpu;
> 
>  	/* only one dump */
>  	local_irq_save(flags);
>  	arch_spin_lock(&ftrace_dump_lock);
> -	if (dump_ran)
> -		goto out;
> -
> -	dump_ran = 1;
> 
>  	tracing_off();
> 
> @@ -5206,7 +5201,6 @@ __ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode)
>  		tracing_on();
>  	}
> 
> - out:
>  	arch_spin_unlock(&ftrace_dump_lock);
>  	local_irq_restore(flags);
>  }


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