From: Nam Cao namcao@linutronix.de
[ Upstream commit 8f02e3563bb5824eb01c94f2c75f1dcee2d05625 ]
Some users of hrtimer need to change the callback function after the initial setup. They write to hrtimer::function directly.
That's not safe under all circumstances as the write is lockless and a concurrent timer expiry might end up using the wrong function pointer.
Introduce hrtimer_update_function(), which also performs runtime checks whether it is safe to modify the callback.
This allows to make hrtimer::function private once all users are converted.
Signed-off-by: Nam Cao namcao@linutronix.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/all/20a937b0ae09ad54b5b6d86eabead7c570f1b72e.1730386... Stable-dep-of: 267ee93c417e ("serial: xilinx_uartps: fix rs485 delay_rts_after_send") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/hrtimer.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 6caaa62d2b1f..39fbeb64a7da 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -337,6 +337,28 @@ static inline int hrtimer_callback_running(struct hrtimer *timer) return timer->base->running == timer; }
+/** + * hrtimer_update_function - Update the timer's callback function + * @timer: Timer to update + * @function: New callback function + * + * Only safe to call if the timer is not enqueued. Can be called in the callback function if the + * timer is not enqueued at the same time (see the comments above HRTIMER_STATE_ENQUEUED). + */ +static inline void hrtimer_update_function(struct hrtimer *timer, + enum hrtimer_restart (*function)(struct hrtimer *)) +{ + guard(raw_spinlock_irqsave)(&timer->base->cpu_base->lock); + + if (WARN_ON_ONCE(hrtimer_is_queued(timer))) + return; + + if (WARN_ON_ONCE(!function)) + return; + + timer->function = function; +} + /* Forward a hrtimer so it expires after now: */ extern u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);