linux-kernel - [PATCH v9 09/32] timers: Split out forward timer base functionality

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Message-Id: <20231201092654.34614-10-anna-maria@linutronix.de>
Date:   Fri,  1 Dec 2023 10:26:31 +0100
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 v9 09/32] timers: Split out forward timer base functionality

Forwarding timer base is done when the next expiry value is calculated and
when a new timer is enqueued. When the next expiry value is calculated the
jiffies value is already available and does not need to be reread a second
time.

Splitting out the forward timer base functionality to make it executable
via both contextes - those where jiffies are already known and those, where
jiffies need to be read.

No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
---
 kernel/time/timer.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 66bac56909ba..e289cbd84e8c 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -939,30 +939,34 @@ get_target_base(struct timer_base *base, unsigned tflags)
 	return get_timer_this_cpu_base(tflags);
 }
 
-static inline void forward_timer_base(struct timer_base *base)
+static inline void __forward_timer_base(struct timer_base *base,
+					unsigned long basej)
 {
-	unsigned long jnow = READ_ONCE(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 (time_before_eq(jnow, base->clk))
+	if (time_before_eq(basej, base->clk))
 		return;
 
 	/*
 	 * If the next expiry value is > jiffies, then we fast forward to
 	 * jiffies otherwise we forward to the next expiry value.
 	 */
-	if (time_after(base->next_expiry, jnow)) {
-		base->clk = jnow;
+	if (time_after(base->next_expiry, basej)) {
+		base->clk = basej;
 	} else {
 		if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
 			return;
 		base->clk = base->next_expiry;
 	}
+
 }
 
+static inline void forward_timer_base(struct timer_base *base)
+{
+	__forward_timer_base(base, READ_ONCE(jiffies));
+}
 
 /*
  * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
-- 
2.39.2