linux-kernel - Re: [PATCH] tracing: erase irqsoff trace with empty write

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Date:   Tue, 19 Sep 2017 10:41:34 -0700
From:   Bo Yan <byan@...dia.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     <mingo@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: erase irqsoff trace with empty write

Steven,

Thanks for review. I have posted the following update

https://lkml.org/lkml/2017/9/18/715

Bo

On 09/18/2017 07:38 AM, Steven Rostedt wrote:
> On Mon, 11 Sep 2017 11:16:35 -0700
> Bo Yan <byan@...dia.com> wrote:
> 
>> One convenient way to erase trace is "echo > trace". However, this
>> is currently broken if the current tracer is irqsoff tracer. This
>> is because irqsoff tracer use max_buffer as the default trace
>> buffer.
>>
>> Set the max_buffer as the one to be cleared when it's the trace
>> buffer currently in use.
> 
> Hi Bo,
> 
> I have no problems with the logic of the patch. But just one nit. The
> tr->trace_buffer has been called "trace_buf" elsewhere in the file. Can
> you resend with using the variable name "trace_buf" instead of "tr_buf"
> just to keep it consistent in the file. It's also been called 'buf' but
> trace_buf would probably be more appropriate.
> 
> Thanks!
> 
> -- Steve
> 
>>
>> Signed-off-by: Bo Yan <byan@...dia.com>
>> ---
>>   kernel/trace/trace.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index 5360b7aec57a..1f91bdd9365b 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -4020,11 +4020,17 @@ static int tracing_open(struct inode *inode, struct file *file)
>>   	/* If this file was open for write, then erase contents */
>>   	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
>>   		int cpu = tracing_get_cpu(inode);
>> +		struct trace_buffer *tr_buf = &tr->trace_buffer;
>> +
>> +#ifdef CONFIG_TRACER_MAX_TRACE
>> +		if (tr->current_trace->print_max)
>> +			tr_buf = &tr->max_buffer;
>> +#endif
>>   
>>   		if (cpu == RING_BUFFER_ALL_CPUS)
>> -			tracing_reset_online_cpus(&tr->trace_buffer);
>> +			tracing_reset_online_cpus(tr_buf);
>>   		else
>> -			tracing_reset(&tr->trace_buffer, cpu);
>> +			tracing_reset(tr_buf, cpu);
>>   	}
>>   
>>   	if (file->f_mode & FMODE_READ) {
>