[PATCH] tracing: erase irqsoff trace with empty write

[PATCH] tracing: erase irqsoff trace with empty write

[Bo Yan]

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.

Signed-off-by: Bo Yan <byan@nvidia.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) {
-- 
2.7.4

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

[Steven Rostedt]

On Mon, 11 Sep 2017 11:16:35 -0700
Bo Yan <byan@nvidia.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@nvidia.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) {

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

[Bo Yan]

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@nvidia.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@nvidia.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) {
> 

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

[Steven Rostedt]

On Tue, 19 Sep 2017 10:41:34 -0700
Bo Yan <byan@nvidia.com> wrote:

> Steven,
> 
> Thanks for review. I have posted the following update
> 
> https://lkml.org/lkml/2017/9/18/715
> 

Yes, I actually applied it. It's pushed to my ftrace/urgent branch, and
I'm currently testing it. If/when it passes I'll be pushing it off to
Linus.

Thanks!

-- Steve