On 2/24/23 19:59, Joel Fernandes wrote:
> On Fri, Feb 24, 2023 at 07:32:22PM -0800, Randy Dunlap wrote:
> [..]
>>> +
>>> + Accept the default if unsure.
>>> +
>>> config RCU_EXP_KTHREAD
>>> bool "Perform RCU expedited work in a real-time kthread"
>>> depends on RCU_BOOST && RCU_EXPERT
>>> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
>>> index 19bf6fa3ee6a..5b73341d9b89 100644
>>> --- a/kernel/rcu/update.c
>>> +++ b/kernel/rcu/update.c
>>> @@ -62,6 +62,10 @@ module_param(rcu_normal_after_boot, int, 0444);
>>> #endif
>>> #endif /* #ifndef CONFIG_TINY_RCU */
>>>
>>> +/* Minimum time until RCU considers boot as completed. */
>>> +static int boot_end_delay = CONFIG_RCU_BOOT_END_DELAY;
>>> +module_param(boot_end_delay, int, 0444);
>>> +
>>> #ifdef CONFIG_DEBUG_LOCK_ALLOC
>>> /**
>>> * rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
>>> @@ -225,12 +229,29 @@ void rcu_unexpedite_gp(void)
>>> EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
>>>
>>> static bool rcu_boot_ended __read_mostly;
>>> -
>>> /*
>>> - * Inform RCU of the end of the in-kernel boot sequence.
>>> + * Inform RCU of the end of the in-kernel boot sequence. The boot sequence will
>>> + * not be marked ended until at least boot_end_delay milliseconds have passed.
>>> */
>>> +void rcu_end_inkernel_boot(void);
>>> +static void boot_rcu_work_fn(struct work_struct *work)
>>> +{
>>> + rcu_end_inkernel_boot();
>>> +}
>>> +static DECLARE_DELAYED_WORK(boot_rcu_work, boot_rcu_work_fn);
>>> +
>>> void rcu_end_inkernel_boot(void)
>>> {
>>> + if (boot_end_delay) {
>>> + u64 boot_ms = ktime_get_boot_fast_ns() / 1000000UL;
>>
>> Is that division OK on 32-bit? Might have to use a helper macro. (I dunno.)
>
> I believe the below should work on 32-bit, but I will test it more. It does
> on 64-bit.
>
> Thanks!
>
> ---8<-----------------------
>
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index cbdad7b46841..2f539c18b310 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -243,7 +243,7 @@ static DECLARE_DELAYED_WORK(boot_rcu_work, boot_rcu_work_fn);
> void rcu_end_inkernel_boot(void)
> {
> if (boot_end_delay) {
> - u64 boot_ms = ktime_get_boot_fast_ns() / 1000000UL;
> + u64 boot_ms = div_u64(ktime_get_boot_fast_ns(), 1000000UL);
>
> if (boot_ms < boot_end_delay) {
> schedule_delayed_work(&boot_rcu_work,
Joel, this now builds cleanly on 32-bit. Before the patch:
ld: kernel/rcu/update.o: in function `boot_rcu_work_fn':
update.c:(.text+0x4623): undefined reference to `__udivdi3'
ld: kernel/rcu/update.o: in function `rcu_end_inkernel_boot':
update.c:(.text+0x46b3): undefined reference to `__udivdi3'
I don't know what the second one refers to, but it didn't show up
after the patch above (using div_u64()).
Thanks.
--
~Randy
