linux-kernel - [tip: timers/core] timers: Restructure internal locking

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Message-ID: <170862192867.398.3423551157545120676.tip-bot2@tip-bot2>
Date: Thu, 22 Feb 2024 17:12:08 -0000
From:
 "tip-bot2 for Richard Cochran (linutronix GmbH)" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Richard Cochran (linutronix GmbH)" <richardcochran@...il.com>,
 "Anna-Maria Behnsen" <anna-maria@...utronix.de>,
 Thomas Gleixner <tglx@...utronix.de>,
 Frederic Weisbecker <frederic@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: timers/core] timers: Restructure internal locking

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     90f5df66c86c259d61aff84e16f519fe1424e1ef
Gitweb:        https://git.kernel.org/tip/90f5df66c86c259d61aff84e16f519fe1424e1ef
Author:        Richard Cochran (linutronix GmbH) <richardcochran@...il.com>
AuthorDate:    Wed, 21 Feb 2024 10:05:42 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 22 Feb 2024 17:52:31 +01:00

timers: Restructure internal locking

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

No functional change.

Signed-off-by: Richard Cochran (linutronix GmbH) <richardcochran@...il.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
Link: https://lore.kernel.org/r/20240221090548.36600-15-anna-maria@linutronix.de

---
 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 bc074c0..51053af 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -2283,11 +2283,7 @@ 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)) {
@@ -2311,21 +2307,36 @@ 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);
 	}
 }