linux-kernel - Re: [PATCH 5/5] rtla/timerlat_top: Abort event processing on second signal

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Message-ID: <fa78c382c1aee2acba2aac11b01ee511414af2dc.camel@redhat.com>
Date: Fri, 17 Jan 2025 07:58:50 +0100
From: Gabriele Monaco <gmonaco@...hat.com>
To: Tomas Glozar <tglozar@...hat.com>, Steven Rostedt <rostedt@...dmis.org>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org, John
 Kacur <jkacur@...hat.com>, Luis Goncalves <lgoncalv@...hat.com>
Subject: Re: [PATCH 5/5] rtla/timerlat_top: Abort event processing on second
 signal

On Thu, 2025-01-16 at 15:49 +0100, Tomas Glozar wrote:
> Apply the changes from the previous patch also to timerlat-top.
> 
> Signed-off-by: Tomas Glozar <tglozar@...hat.com>
> ---
>  tools/tracing/rtla/src/timerlat_top.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/tools/tracing/rtla/src/timerlat_top.c
> b/tools/tracing/rtla/src/timerlat_top.c
> index d21a21053917..d358cd39f360 100644
> --- a/tools/tracing/rtla/src/timerlat_top.c
> +++ b/tools/tracing/rtla/src/timerlat_top.c
> @@ -903,6 +903,14 @@ static int stop_tracing;
>  static struct trace_instance *top_inst = NULL;
>  static void stop_top(int sig)
>  {
> +	if (stop_tracing) {
> +		/*
> +		 * Stop requested twice in a row; abort event
> processing and
> +		 * exit immediately
> +		 */
> +		tracefs_iterate_stop(top_inst->inst);
> +		return;
> +	}
>  	stop_tracing = 1;
>  	if (top_inst)
>  		trace_instance_stop(top_inst);

I confirm the patchset works as expected on a 128 cores machine.
That is like the machine where the problem was first observed: run
timerlat with -p 100 and it would hang.

Now running it with -d terminates (a bit) after the expiration of the
timer with a sane report, sending a SIGINT terminates it too and
sending 2 SIGINT terminates it almost instantaneously.	

This works on both timerlat top and hist, with both -u and -k .
The report only gets printed in the end (as if -q was passed), but
these patches are not meant to fix that.

Tested-by: Gabriele Monaco <gmonaco@...hat.com>