[PATCH] Documentation/rtla: Document SIGINT behavior

[Tomas Glozar <tglozar@redhat.com>]

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@redhat.com>
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---

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@redhat.com/

 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.
+
 EXIT STATUS
 ===========
 
-- 
2.53.0