linux-kernel - [PATCH v8 05/25] timers: Clarify check in forward_timer

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Message-Id: <20231004123454.15691-6-anna-maria@linutronix.de>
Date:   Wed,  4 Oct 2023 14:34:34 +0200
From:   Anna-Maria Behnsen <anna-maria@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        John Stultz <jstultz@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Arjan van de Ven <arjan@...radead.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Lukasz Luba <lukasz.luba@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>,
        Srinivas Pandruvada <srinivas.pandruvada@...el.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: [PATCH v8 05/25] timers: Clarify check in forward_timer_base()

The current check whether a forward of the timer base is required can be
simplified by using an already existing comparison function which is easier
to read. The related comment is outdated and was not updated when the check
changed in commit 36cd28a4cdd0 ("timers: Lower base clock forwarding
threshold").

Use time_before_eq() for the check and replace the comment by copying the
comment from the same check inside get_next_timer_interrupt().

No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
---
 kernel/time/timer.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 5e17244a9465..31aed8353db1 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -944,11 +944,10 @@ static inline void forward_timer_base(struct timer_base *base)
 	unsigned long jnow = READ_ONCE(jiffies);
 
 	/*
-	 * No need to forward if we are close enough below jiffies.
-	 * Also while executing timers, base->clk is 1 offset ahead
-	 * of jiffies to avoid endless requeuing to current jiffies.
+	 * Check whether we can forward the base. We can only do that when
+	 * @basej is past base->clk otherwise we might rewind base->clk.
 	 */
-	if ((long)(jnow - base->clk) < 1)
+	if (time_before_eq(jnow, base->clk))
 		return;
 
 	/*
-- 
2.39.2