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@gmail.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240221090548.36600-15-anna-maria@linutronix.de

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index bc074c0..51053af 100644 (file)
--- 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);
        }
 }