linux-kernel - [PATCH v11 09/20] timers: Split next timer interrupt logic

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Message-Id: <20240221090548.36600-10-anna-maria@linutronix.de>
Date: Wed, 21 Feb 2024 10:05:37 +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>,
	Christian Loehle <christian.loehle@....com>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: [PATCH v11 09/20] timers: Split next timer interrupt logic

Split the logic for getting next timer interrupt (no matter of recalculated
or already stored in base->next_expiry) into a separate function named
next_timer_interrupt(). Make it available to local call sites only.

No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
---
v10: Reword commit message

v9: Adapt to the fix for empty timer bases.
---
 kernel/time/timer.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 793848167852..4d6cf49a2fd1 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1951,12 +1951,29 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
 	return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
 }
 
+static unsigned long next_timer_interrupt(struct timer_base *base,
+					  unsigned long basej)
+{
+	if (base->next_expiry_recalc)
+		next_expiry_recalc(base);
+
+	/*
+	 * Move next_expiry for the empty base into the future to prevent an
+	 * unnecessary raise of the timer softirq when the next_expiry value
+	 * will be reached even if there is no timer pending.
+	 */
+	if (!base->timers_pending)
+		base->next_expiry = basej + NEXT_TIMER_MAX_DELTA;
+
+	return base->next_expiry;
+}
+
 static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,
 					     bool *idle)
 {
 	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
-	unsigned long nextevt = basej + NEXT_TIMER_MAX_DELTA;
 	u64 expires = KTIME_MAX;
+	unsigned long nextevt;
 
 	/*
 	 * Pretend that there is no timer pending if the cpu is offline.
@@ -1969,24 +1986,13 @@ static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,
 	}
 
 	raw_spin_lock(&base->lock);
-	if (base->next_expiry_recalc)
-		next_expiry_recalc(base);
+	nextevt = next_timer_interrupt(base, basej);
 
 	if (base->timers_pending) {
-		nextevt = base->next_expiry;
-
 		/* If we missed a tick already, force 0 delta */
 		if (time_before(nextevt, basej))
 			nextevt = basej;
 		expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
-	} else {
-		/*
-		 * Move next_expiry for the empty base into the future to
-		 * prevent a unnecessary raise of the timer softirq when the
-		 * next_expiry value will be reached even if there is no timer
-		 * pending.
-		 */
-		base->next_expiry = nextevt;
 	}
 
 	/*
-- 
2.39.2