linux-kernel - Re: [PATCH 1/5] tracing: Fix initialization failure path in tracing_set

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Date:	Wed, 30 May 2012 15:44:28 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Anton Vorontsov <anton.vorontsov@...aro.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kees Cook <keescook@...omium.org>,
	Colin Cross <ccross@...roid.com>,
	Tony Luck <tony.luck@...el.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	John Stultz <john.stultz@...aro.org>,
	Shuah Khan <shuahkhan@...il.com>, arve@...roid.com,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	Jesper Juhl <jj@...osbits.net>,
	Randy Dunlap <rdunlap@...otime.net>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Thomas Meyer <thomas@...3r.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marco Stornelli <marco.stornelli@...il.com>,
	WANG Cong <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	linaro-kernel@...ts.linaro.org, patches@...aro.org,
	kernel-team@...roid.com
Subject: Re: [PATCH 1/5] tracing: Fix initialization failure path in
 tracing_set_tracer()

On Sat, 2012-05-26 at 06:39 -0700, Anton Vorontsov wrote:
> If tracer->init() fails, current code will leave current_tracer pointing
> to an unusable tracer, which at best makes 'current_tracer' report
> inaccurate value.
> 
> Fix the issue by pointing current_tracer to nop tracer, and only update
> current_tracer with the new one after all the initialization succeeds.
> 

Hmm, I'll look at this in more detail. This may be something I pull now.
(for 3.6).

-- Steve

> Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
> ---
>  kernel/trace/trace.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 68032c6..5cf7e67 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3172,10 +3172,10 @@ static int tracing_set_tracer(const char *buf)
>  	}
>  	destroy_trace_option_files(topts);
>  
> -	current_trace = t;
> +	current_trace = &nop_trace;
>  
> -	topts = create_trace_option_files(current_trace);
> -	if (current_trace->use_max_tr) {
> +	topts = create_trace_option_files(t);
> +	if (t->use_max_tr) {
>  		int cpu;
>  		/* we need to make per cpu buffer sizes equivalent */
>  		for_each_tracing_cpu(cpu) {
> @@ -3195,6 +3195,7 @@ static int tracing_set_tracer(const char *buf)
>  			goto out;
>  	}
>  
> +	current_trace = t;
>  	trace_branch_enable(tr);
>   out:
>  	mutex_unlock(&trace_types_lock);


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