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From: Anna-Maria Behnsen <anna-maria@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
	John Stultz <jstultz@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Eric Dumazet <edumazet@google.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Arjan van de Ven <arjan@infradead.org>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Rik van Riel <riel@surriel.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Sebastian Siewior <bigeasy@linutronix.de>,
	Giovanni Gherdovich <ggherdovich@suse.cz>,
	Lukasz Luba <lukasz.luba@arm.com>,
	"Gautham R . Shenoy" <gautham.shenoy@amd.com>,
	Srinivas Pandruvada <srinivas.pandruvada@intel.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Christian Loehle <christian.loehle@arm.com>,
	"Richard Cochran (linutronix GmbH)" <richardcochran@gmail.com>,
	Anna-Maria Behnsen <anna-maria@linutronix.de>
Subject: [PATCH v11 14/20] timers: Restructure internal locking
Date: Wed, 21 Feb 2024 10:05:42 +0100
Message-Id: <20240221090548.36600-15-anna-maria@linutronix.de>
In-Reply-To: <20240221090548.36600-1-anna-maria@linutronix.de>
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From: "Richard Cochran (linutronix GmbH)" <richardcochran@gmail.com>

Move the locking out from __run_timers() to the call sites, so the
protected section can be extended at the call site. Preparatory patch for
changing the NOHZ timer placement to a pull at expiry time model.

No functional change.

Signed-off-by: Richard Cochran (linutronix GmbH) <richardcochran@gmail.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/time/timer.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 88160b3461e0..52af50d00ae6 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -2238,11 +2238,7 @@ static inline void __run_timers(struct timer_base *base)
 	struct hlist_head heads[LVL_DEPTH];
 	int levels;
 
-	if (time_before(jiffies, base->next_expiry))
-		return;
-
-	timer_base_lock_expiry(base);
-	raw_spin_lock_irq(&base->lock);
+	lockdep_assert_held(&base->lock);
 
 	while (time_after_eq(jiffies, base->clk) &&
 	       time_after_eq(jiffies, base->next_expiry)) {
@@ -2266,21 +2262,36 @@ static inline void __run_timers(struct timer_base *base)
 		while (levels--)
 			expire_timers(base, heads + levels);
 	}
+}
+
+static void __run_timer_base(struct timer_base *base)
+{
+	if (time_before(jiffies, base->next_expiry))
+		return;
+
+	timer_base_lock_expiry(base);
+	raw_spin_lock_irq(&base->lock);
+	__run_timers(base);
 	raw_spin_unlock_irq(&base->lock);
 	timer_base_unlock_expiry(base);
 }
 
+static void run_timer_base(int index)
+{
+	struct timer_base *base = this_cpu_ptr(&timer_bases[index]);
+
+	__run_timer_base(base);
+}
+
 /*
  * This function runs timers and the timer-tq in bottom half context.
  */
 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
 {
-	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_LOCAL]);
-
-	__run_timers(base);
+	run_timer_base(BASE_LOCAL);
 	if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
-		__run_timers(this_cpu_ptr(&timer_bases[BASE_GLOBAL]));
-		__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
+		run_timer_base(BASE_GLOBAL);
+		run_timer_base(BASE_DEF);
 	}
 }
 
-- 
2.39.2