linux-kernel - [PATCH v1 1/5] cpuidle: governors: teo: Avoid selecting states with zero-size bins

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <3033265.e9J7NaK4W3@rafael.j.wysocki>
Date: Wed, 14 Jan 2026 20:44:04 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Christian Loehle <christian.loehle@....com>,
 Doug Smythies <dsmythies@...us.net>
Subject:
 [PATCH v1 1/5] cpuidle: governors: teo: Avoid selecting states with zero-size
 bins

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

If the last two enabled idle states have the same target residency which
is at least equal to TICK_NSET, teo may select the next-to-last one even
though the size of that state's bin is 0, which is confusing.

Prevent that from happening by adding a target residency check to the
relevant code path.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpuidle/governors/teo.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/drivers/cpuidle/governors/teo.c
+++ b/drivers/cpuidle/governors/teo.c
@@ -388,6 +388,15 @@ static int teo_select(struct cpuidle_dri
 			while (min_idx < idx &&
 			       drv->states[min_idx].target_residency_ns < TICK_NSEC)
 				min_idx++;
+
+			/*
+			 * Avoid selecting a state with a lower index, but with
+			 * the same target residency as the current candidate
+			 * one.
+			 */
+			if (drv->states[min_idx].target_residency_ns ==
+					drv->states[idx].target_residency_ns)
+				goto constraint;
 		}

 		/*
@@ -410,6 +419,7 @@ static int teo_select(struct cpuidle_dri
 		}
 	}

+constraint:
 	/*
 	 * If there is a latency constraint, it may be necessary to select an
 	 * idle state shallower than the current candidate one.