On 2025/4/25 07:59, John Stultz wrote:
On Thu, Apr 24, 2025 at 7:48 AM Su Hui <suhui@xxxxxxxxxxxx> wrote:
There are two code styles for the lock in alarmtimer, guard() and
spin_{lock,unlock}_irqsave(). Switch all these to guard() to make code
neater.
Thanks for sending this out! A few comments below.
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index e5450a77ada9..920a3544d0cd 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -70,12 +70,10 @@ static DEFINE_SPINLOCK(rtcdev_lock);
*/
struct rtc_device *alarmtimer_get_rtcdev(void)
{
- unsigned long flags;
struct rtc_device *ret;
- spin_lock_irqsave(&rtcdev_lock, flags);
- ret = rtcdev;
- spin_unlock_irqrestore(&rtcdev_lock, flags);
+ scoped_guard(spinlock_irqsave, &rtcdev_lock)
+ ret = rtcdev;
return ret;
This seems like it could be simplified further to just:
{
guard(spinlock_irqsave, &rtcdev_lock);
return rtcdev;
}
No?
Yes, it's better. I can update this in v2.
- spin_lock_irqsave(&freezer_delta_lock, flags);
- min = freezer_delta;
- expires = freezer_expires;
- type = freezer_alarmtype;
- freezer_delta = 0;
- spin_unlock_irqrestore(&freezer_delta_lock, flags);
+ scoped_guard(spinlock_irqsave, &freezer_delta_lock) {
+ min = freezer_delta;
+ expires = freezer_expires;
+ type = freezer_alarmtype;
+ freezer_delta = 0;
+ }
I'm not necessarily opposed, but I'm not sure we're gaining much here.
I can remove this in v2.
@@ -352,13 +347,13 @@ EXPORT_SYMBOL_GPL(alarm_init);
void alarm_start(struct alarm *alarm, ktime_t start)
{
struct alarm_base *base = &alarm_bases[alarm->type];
- unsigned long flags;
- spin_lock_irqsave(&base->lock, flags);
- alarm->node.expires = start;
- alarmtimer_enqueue(base, alarm);
- hrtimer_start(&alarm->timer, alarm->node.expires, HRTIMER_MODE_ABS);
- spin_unlock_irqrestore(&base->lock, flags);
+ scoped_guard(spinlock_irqsave, &base->lock) {
+ alarm->node.expires = start;
+ alarmtimer_enqueue(base, alarm);
+ hrtimer_start(&alarm->timer, alarm->node.expires,
+ HRTIMER_MODE_ABS);
+ }
Similarly, this just seems more like churn, than making the code
particularly more clear.
I can remove this in v2 too.
Overall, there's a few nice cleanups in this one, but there's also
some that I'd probably leave be. I personally don't see
straightforward explicit lock/unlocks as an anti-patern, but the guard
logic definitely helps cleanup some of the uglier goto unlock
patterns, which is a nice benefit. One argument I can see for pushing
to switch even the simple lock/unlock usage, is that having both
models used makes the code less consistent, and adds mental load to
the reader, but there's a lot of complex locking that can't be done
easily with guard() so I don't know if we will ever be able to excise
all the explicit lock/unlock calls, and the extra indentation for
those scoped_guard sections can cause readability problems on its own
as well.
Understand, thanks for your suggestions!
I will send a v2 patch to update these points later if there is no more
other
suggestion.
Su Hui
