linux-kernel - [PATCH v1] cpuidle: Add sanity check for exit latency and target residency

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Message-ID: <5939579.DvuYhMxLoT@rafael.j.wysocki>
Date: Fri, 07 Nov 2025 19:19:21 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Subject:
 [PATCH v1] cpuidle: Add sanity check for exit latency and target residency

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Make __cpuidle_driver_init() sanitize CPU idle states so that the exit
latency of a given state is not greater than its target residency which
would break cpuidle assumptions.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpuidle/driver.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -193,6 +193,16 @@ static void __cpuidle_driver_init(struct
 			s->exit_latency_ns =  0;
 		else
 			s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC);
+
+		/*
+		 * Ensure that the exit latency of a CPU idle state does not
+		 * exceed its target residency which is assumed in cpuidle in
+		 * multiple places.
+		 */
+		if (s->exit_latency_ns > s->target_residency_ns) {
+			s->target_residency_ns = s->exit_latency_ns;
+			s->target_residency = s->exit_latency;
+		}
 	}
 }