linux-kernel - [PATCH v5 14/18] timer: Check if timers base is handled already

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Message-Id: <20230301141744.16063-15-anna-maria@linutronix.de>
Date:   Wed,  1 Mar 2023 15:17:40 +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 <fweisbec@...il.com>,
        Rik van Riel <riel@...riel.com>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: [PATCH v5 14/18] timer: Check if timers base is handled already

Due to the conversion of the NOHZ timer placement to a pull at expiry
time model, the per CPU timer bases with non pinned timers are no
longer handled only by the local CPU. In case a remote CPU already
expires the non pinned timers base of the local cpu, nothing more
needs to be done by the local CPU. A check at the begin of the expire
timers routine is required, because timer base lock is dropped before
executing the timer callback function.

This is a preparatory work, but has no functional impact right now.

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

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index be085e94afcc..9553da99e262 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -2144,6 +2144,9 @@ static inline void __run_timers(struct timer_base *base)
 
 	lockdep_assert_held(&base->lock);
 
+	if (!!base->running_timer)
+		return;
+
 	while (time_after_eq(jiffies, base->clk) &&
 	       time_after_eq(jiffies, base->next_expiry)) {
 		levels = collect_expired_timers(base, heads);
-- 
2.30.2