[PATCH 6.12 545/567] hrtimers: Make hrtimer_update_function() less expensive

Greg Kroah-Hartman
2026-01-06T17:44:27Z

From: Thomas Gleixner <tglx@linutronix.de>

commit 2ea97b76d6712bfb0408e5b81ffd7bc4551d3153 upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/hrtimer.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -348,6 +348,7 @@ static inline int hrtimer_callback_runni
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)))
@@ -355,7 +356,7 @@ static inline void hrtimer_update_functi

if (WARN_ON_ONCE(!function))
return;
-
+#endif
timer->function = function;
}