linux-kernel - [PATCH 4.16 51/52] clocksource: Consistent de-rate when marking unstable

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Message-Id: <20180508073935.333431008@linuxfoundation.org>
Date:   Tue,  8 May 2018 10:10:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        len.brown@...el.com, rjw@...ysocki.net, diego.viola@...il.com,
        rui.zhang@...el.com
Subject: [PATCH 4.16 51/52] clocksource: Consistent de-rate when marking unstable

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@...radead.org>

commit cd2af07d823e5287cd6c91d54337348c2a873462 upstream.

When a registered clocksource gets marked unstable the watchdog_kthread
will de-rate and re-select the clocksource. Ensure it also de-rates
when getting called on an unregistered clocksource.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: len.brown@...el.com
Cc: rjw@...ysocki.net
Cc: diego.viola@...il.com
Cc: rui.zhang@...el.com
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180430100344.594904898@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/time/clocksource.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -152,12 +152,19 @@ static void __clocksource_unstable(struc
 	cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
 	cs->flags |= CLOCK_SOURCE_UNSTABLE;

-	if (list_empty(&cs->list))
+	/*
+	 * If the clocksource is registered clocksource_watchdog_kthread() will
+	 * re-rate and re-select.
+	 */
+	if (list_empty(&cs->list)) {
+		cs->rating = 0;
 		return;
+	}

 	if (cs->mark_unstable)
 		cs->mark_unstable(cs);

+	/* kick clocksource_watchdog_kthread() */
 	if (finished_booting)
 		schedule_work(&watchdog_work);
 }