hrtimers: Make hrtimer_update_function() less expensive

The sanity checks in hrtimer_update_function() are expensive for high
frequency usage like in the io/uring code due to locking.

Hide the sanity checks behind CONFIG_PROVE_LOCKING, which has a decent
chance to be enabled on a regular basis for testing.

Fixes: 8f02e3563bb5 ("hrtimers: Introduce hrtimer_update_function()")
Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/87ikpllali.ffs@tglx

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index f7bfdcf0dda3f12dd7216ff51471f32647c70ab5..bdd55c1f0d73e69976ca94475bcebfb1c1cf4a1d 100644 (file)
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -333,6 +333,7 @@ static inline int hrtimer_callback_running(struct hrtimer *timer)
 static inline void hrtimer_update_function(struct hrtimer *timer,
                                           enum hrtimer_restart (*function)(struct hrtimer *))
 {
+#ifdef CONFIG_PROVE_LOCKING
        guard(raw_spinlock_irqsave)(&timer->base->cpu_base->lock);
 
        if (WARN_ON_ONCE(hrtimer_is_queued(timer)))
@@ -340,7 +341,7 @@ static inline void hrtimer_update_function(struct hrtimer *timer,
 
        if (WARN_ON_ONCE(!function))
                return;
-
+#endif
        timer->function = function;
 }