linux-kernel - [for-next][PATCH 04/16] rtla/timerlat

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Message-ID: <20251120232707.946976394@kernel.org>
Date: Thu, 20 Nov 2025 18:23:27 -0500
From: Steven Rostedt <rostedt@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Tomas Glozar <tglozar@...hat.com>,
 John Kacur <jkacur@...hat.com>,
 stable@...r.kernel.org,
 Wander Lairson Costa <wander@...hat.com>
Subject: [for-next][PATCH 04/16] rtla/timerlat_bpf: Stop tracing on user latency

From: Tomas Glozar <tglozar@...hat.com>

rtla-timerlat allows a *thread* latency threshold to be set via the
-T/--thread option. However, the timerlat tracer calls this *total*
latency (stop_tracing_total_us), and stops tracing also when the
return-to-user latency is over the threshold.

Change the behavior of the timerlat BPF program to reflect what the
timerlat tracer is doing, to avoid discrepancy between stopping
collecting data in the BPF program and stopping tracing in the timerlat
tracer.

Cc: stable@...r.kernel.org
Fixes: e34293ddcebd ("rtla/timerlat: Add BPF skeleton to collect samples")
Reviewed-by: Wander Lairson Costa <wander@...hat.com>
Link: https://lore.kernel.org/r/20251006143100.137255-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@...hat.com>
---
 tools/tracing/rtla/src/timerlat.bpf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/tracing/rtla/src/timerlat.bpf.c b/tools/tracing/rtla/src/timerlat.bpf.c
index 084cd10c21fc..e2265b5d6491 100644
--- a/tools/tracing/rtla/src/timerlat.bpf.c
+++ b/tools/tracing/rtla/src/timerlat.bpf.c
@@ -148,6 +148,9 @@ int handle_timerlat_sample(struct trace_event_raw_timerlat_sample *tp_args)
 	} else {
 		update_main_hist(&hist_user, bucket);
 		update_summary(&summary_user, latency, bucket);
+
+		if (thread_threshold != 0 && latency_us >= thread_threshold)
+			set_stop_tracing();
 	}
 
 	return 0;
-- 
2.51.0