linux-kernel - [PATCH] tick: Remove unreasonable detached state set in tick

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Message-Id: <20250807035954.2412399-1-maobibo@loongson.cn>
Date: Thu,  7 Aug 2025 11:59:54 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] tick: Remove unreasonable detached state set in tick_shutdown()

Function clockevents_switch_state() will check whether it has already
switched to specified state, do nothing if it has.

In function tick_shutdown(), it will set detached state at first and
call clockevents_switch_state() in clockevents_exchange_device(). The
function clockevents_switch_state() will do nothing since it is already
detached state. So the tick timer device will not be shutdown when CPU
is offline. In guest VM system, timer interrupt will prevent vCPU to sleep
if vCPU is hot removed.

Here remove state set before calling clockevents_exchange_device(),
its state will be set in function clockevents_switch_state() if it
succeeds to do so.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 kernel/time/tick-common.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 9a3859443c04..eb9b777f5492 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -424,11 +424,6 @@ void tick_shutdown(unsigned int cpu)

 	td->mode = TICKDEV_MODE_PERIODIC;
 	if (dev) {
-		/*
-		 * Prevent that the clock events layer tries to call
-		 * the set mode function!
-		 */
-		clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
 		clockevents_exchange_device(dev, NULL);
 		dev->event_handler = clockevents_handle_noop;
 		td->evtdev = NULL;

base-commit: 7e161a991ea71e6ec526abc8f40c6852ebe3d946
-- 
2.39.3