timers/migration: Spare write when nothing changed

The wakeup value is written unconditionally in tmigr_cpu_new_timer(). When
there was no new next timer expiry that needs to be propagated, then the
value that was read before is written. This is not required.

Move the write to the place where wakeup value is changed changed.

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/20240716-tmigr-fixes-v4-7-757baa7803fe@linutronix.de

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index ca76120ee7c6a9d9cb114195d970d1366c7a3121..9c15ae8d8a25343fac52217075b3de152c47053c 100644 (file)
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1215,14 +1215,13 @@ u64 tmigr_cpu_new_timer(u64 nextexp)
                if (nextexp != tmc->cpuevt.nextevt.expires ||
                    tmc->cpuevt.ignore) {
                        ret = tmigr_new_timer(tmc, nextexp);
+                       /*
+                        * Make sure the reevaluation of timers in idle path
+                        * will not miss an event.
+                        */
+                       WRITE_ONCE(tmc->wakeup, ret);
                }
        }
-       /*
-        * Make sure the reevaluation of timers in idle path will not miss an
-        * event.
-        */
-       WRITE_ONCE(tmc->wakeup, ret);
-
        trace_tmigr_cpu_new_timer_idle(tmc, nextexp);
        raw_spin_unlock(&tmc->lock);
        return ret;