clockevents: Improve clockevents_notify_released() comment

When a new clockevent device is added and replaces a previous device,
the latter is put into the released list. Then the released list is
added back.

This may look counter-intuitive but the reason is that released device
might be suitable for other uses. For example a released CPU regular
clockevent can be a better replacement for the current broadcast event.
Similarly a released broadcast clockevent can be a better replacement
for the current regular clockevent of a given CPU.

Improve comments stating about these subtleties.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241029125451.54574-2-frederic@kernel.org

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 78c7bd64d0ddf70d164db298708487916436173f..4af27994db93c38c22c769c463f44db2f6d165d8 100644 (file)
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -337,13 +337,21 @@ int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 }
 
 /*
- * Called after a notify add to make devices available which were
- * released from the notifier call.
+ * Called after a clockevent has been added which might
+ * have replaced a current regular or broadcast device. A
+ * released normal device might be a suitable replacement
+ * for the current broadcast device. Similarly a released
+ * broadcast device might be a suitable replacement for a
+ * normal device.
  */
 static void clockevents_notify_released(void)
 {
        struct clock_event_device *dev;
 
+       /*
+        * Keep iterating as long as tick_check_new_device()
+        * replaces a device.
+        */
        while (!list_empty(&clockevents_released)) {
                dev = list_entry(clockevents_released.next,
                                 struct clock_event_device, list);