Re: [PATCH] Documentation/rtla: Document SIGINT behavior

[Steven Rostedt]

On Tue, 24 Mar 2026 13:32:29 +0100
Tomas Glozar <tglozar@xxxxxxxxxx> wrote:

> The behavior of RTLA on receiving SIGINT is currently undocumented.
> 
> Describe it in RTLA's common appendix that appears in man pages for all
> RTLA tools to avoid confusion.
> 
> Suggested-by: Attila Fazekas <afazekas@xxxxxxxxxx>
> Signed-off-by: Tomas Glozar <tglozar@xxxxxxxxxx>
> ---
> 
> Note: There was a bug in SIGINT behavior, fixed in upcoming commit [1].
> 
> [1] https://lore.kernel.org/linux-trace-kernel/20260310160725.144443-1-tglozar@xxxxxxxxxx/

Hmm, this may be interesting enough to add to the change log itself.

> 
>  Documentation/tools/rtla/common_appendix.txt | 21 ++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/Documentation/tools/rtla/common_appendix.txt b/Documentation/tools/rtla/common_appendix.txt
> index 53cae7537537..8c90a02588e7 100644
> --- a/Documentation/tools/rtla/common_appendix.txt
> +++ b/Documentation/tools/rtla/common_appendix.txt
> @@ -1,5 +1,26 @@
>  .. SPDX-License-Identifier: GPL-2.0
>  
> +SIGINT BEHAVIOR
> +===============
> +
> +On the first SIGINT, RTLA exits after collecting all outstanding samples up to
> +the point of receiving the signal.
> +
> +When receiving more than one SIGINT, RTLA discards any outstanding samples, and
> +exits while displaying only samples that have already been processed.
> +
> +If SIGINT is received during RTLA cleanup, RTLA exits immediately via
> +the default signal handler.
> +
> +Note: For the purpose of SIGINT behavior, the expiry of duration specified via
> +the -d/--duration option is treated as equivalent to receiving a SIGINT. For
> +example, a SIGINT received after duration expired but samples have not been
> +processed yet will drop any outstanding samples.
> +
> +Also note that when using the timerlat tool in BPF mode, samples are processed
> +in-kernel; RTLA only copies them out to display them to the user. A second
> +SIGINT does not affect in-kernel sample aggregation.

But does it affect the user space side of reading that information?

> +
>  EXIT STATUS
>  ===========
>  

Other than that ... LGTM,

Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

-- Steve