linux-kernel - Re: [PATCH] tracing/osnoise: Fix notify new tracing_max

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Date:   Wed, 29 Mar 2023 08:31:33 +0200
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] tracing/osnoise: Fix notify new tracing_max_latency

On 3/29/23 01:16, Steven Rostedt wrote:
> On Fri, 24 Mar 2023 18:51:35 +0100
> Daniel Bristot de Oliveira <bristot@...nel.org> wrote:
> 
>> timerlat is not reporting a new tracing_max_latency for the thread
>> latency. Also, the tracer is reporting new max latency on instances
>> where the tracing is off, creating inconsistencies between the max
>> reported values in the trace and in the tracing_max_latency. Thus
>> only report new tracing_max_latency on active tracing instances.
> 
> Sounds to me this patch fixes two different bugs. If so, can you please
> break it up into two different patches?

Yeah, I was dubious about sending one or two patches when I sent this one... But
it makes sense making two of them... so I will do.

Thanks!

-- Daniel

> Thanks!
> 
> -- Steve
> 
>>
>> Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
>> Cc: Daniel Bristot de Oliveira <bristot@...nel.org>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: Masami Hiramatsu <mhiramat@...nel.org>
>> Signed-off-by: Daniel Bristot de Oliveira <bristot@...nel.org>
>> ---
>>  kernel/trace/trace_osnoise.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
>> index 210e1f168392..2a1b337ac643 100644
>> --- a/kernel/trace/trace_osnoise.c
>> +++ b/kernel/trace/trace_osnoise.c
>> @@ -1296,7 +1296,7 @@ static void notify_new_max_latency(u64 latency)
>>  	rcu_read_lock();
>>  	list_for_each_entry_rcu(inst, &osnoise_instances, list) {
>>  		tr = inst->tr;
>> -		if (tr->max_latency < latency) {
>> +		if (tracer_tracing_is_on(tr) && tr->max_latency < latency) {
>>  			tr->max_latency = latency;
>>  			latency_fsnotify(tr);
>>  		}
>> @@ -1738,6 +1738,8 @@ static int timerlat_main(void *data)
>>  
>>  		trace_timerlat_sample(&s);
>>  
>> +		notify_new_max_latency(diff);
>> +
>>  		timerlat_dump_stack(time_to_us(diff));
>>  
>>  		tlat->tracing_thread = false;
>