[PATCH V2 1/2] tracing/timerlat: Notify new max thread latency

[PATCH V2 1/2] tracing/timerlat: Notify new max thread latency

[Daniel Bristot de Oliveira]

timerlat is not reporting a new tracing_max_latency for the thread
latency. The reason is that it is not calling notify_new_max_latency()
function after the new thread latency is sampled.

Call notify_new_max_latency after computing the thread latency.

Changes from V1:
 Split the patch into two patches (Steve)

Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
---
 kernel/trace/trace_osnoise.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 9176bb7a9bb4..e8116094bed8 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -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;
-- 
2.38.1

[PATCH V2 2/2] tracing/osnoise: Fix notify new tracing_max_latency

[Daniel Bristot de Oliveira]

osnoise/timerlat tracers are 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.

Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
---
 kernel/trace/trace_osnoise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index e8116094bed8..4496975f2029 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);
 		}
-- 
2.38.1

Re: [PATCH V2 1/2] tracing/timerlat: Notify new max thread latency

[Steven Rostedt]

On Wed, 29 Mar 2023 17:50:15 +0200
Daniel Bristot de Oliveira <bristot@kernel.org> wrote:

> timerlat is not reporting a new tracing_max_latency for the thread
> latency. The reason is that it is not calling notify_new_max_latency()
> function after the new thread latency is sampled.
> 
> Call notify_new_max_latency after computing the thread latency.
> 
> Changes from V1:
>  Split the patch into two patches (Steve)

FYI, when doing this, please place the updates below the "---"

That way it doesn't automatically end up in the git log, and I have to go
back in and remove it.

> 
> Fixes: dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr")
> Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
> ---

Here, you can add:

Changes from V1: https://lore.kernel.org/linux-trace-kernel/c22302a7db3cee6bcabf87462ed22a35dd38690f.1679675521.git.bristot@kernel.org/
  Split the patch into two patches (Steve)

Notice, that I also added the link to the previous version, so it's easy to
find if someone wanted to investigate this series.

-- Steve



>  kernel/trace/trace_osnoise.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
> index 9176bb7a9bb4..e8116094bed8 100644
> --- a/kernel/trace/trace_osnoise.c
> +++ b/kernel/trace/trace_osnoise.c
> @@ -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;