linux-kernel - [PATCH v1] cpuidle: Do not return from cpuidle_play

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Message-ID: <4992010.31r3eYUQgx@rjwysocki.net>
Date: Thu, 14 Nov 2024 18:46:20 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, x86 Maintainers <x86@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
 Mario Limonciello <mario.limonciello@....com>
Subject:
 [PATCH v1] cpuidle: Do not return from cpuidle_play_dead() on callback
 failures

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

If the :enter_dead() idle state callback fails for a certain state,
there may be still a shallower state for which it will work.

Because the only caller of cpuidle_play_dead(), native_play_dead(),
falls back to hlt_play_dead() if it returns an error, it should
better try all of the idle states for which :enter_dead() is present
before failing, so change it accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/cpuidle/cpuidle.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: linux-pm/drivers/cpuidle/cpuidle.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/cpuidle.c
+++ linux-pm/drivers/cpuidle/cpuidle.c
@@ -70,9 +70,10 @@ int cpuidle_play_dead(void)
 		return -ENODEV;

 	/* Find lowest-power state that supports long-term idle */
-	for (i = drv->state_count - 1; i >= 0; i--)
-		if (drv->states[i].enter_dead)
-			return drv->states[i].enter_dead(dev, i);
+	for (i = drv->state_count - 1; i >= 0; i--) {
+		if (drv->states[i].enter_dead && !drv->states[i].enter_dead(dev, i))
+			return 0;
+	}

 	return -ENODEV;
 }