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

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Message-ID: <5164B3F0.2030506@lge.com>
Date:	Wed, 10 Apr 2013 09:36:00 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Namhyung Kim <namhyung@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] tracing: Check cpu file on tracing_release()

Hi Steve,

2013-04-10 오전 9:31, Steven Rostedt 쓴 글:
> 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.

You meant iter->cpu_file != RING_BUFFER_ALL_CPUS case, right?

So why bother trying to check other cpus then?

Thanks,
Namhyung

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