linux-kernel - Re: [PATCH 3/3] tracing: Check cpu file on tracing

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Date:	Tue, 09 Apr 2013 20:31:03 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH 3/3] tracing: Check cpu file on tracing_release()

On Wed, 2013-04-10 at 09:18 +0900, Namhyung Kim wrote:
> From: Namhyung Kim <namhyung.kim@....com>
> 
> It looks like tracing_release() lacks checking iter->cpu_file so that
> closing a per_cpu trace file would attempt to close all cpu buffers.
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  kernel/trace/trace.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 7270460cfe3c..0beddcb80509 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2883,7 +2883,13 @@ static int tracing_release(struct inode *inode, struct file *file)
>  	WARN_ON(!tr->ref);
>  	tr->ref--;
>  
> -	for_each_tracing_cpu(cpu) {
> +	if (iter->cpu_file == RING_BUFFER_ALL_CPUS) {
> +		for_each_tracing_cpu(cpu) {
> +			if (iter->buffer_iter[cpu])

Only the cpu that is assigned gets buffer_iter[cpu] set. The other
buffer_iter[cpus] will simply be ignored.

-- Steve

> +				ring_buffer_read_finish(iter->buffer_iter[cpu]);
> +		}
> +	} else {
> +		cpu = iter->cpu_file;
>  		if (iter->buffer_iter[cpu])
>  			ring_buffer_read_finish(iter->buffer_iter[cpu]);
>  	}


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