Re: [PATCH v4 1/3] time: add "NOW() good" indicator

On 28.07.2026 10:17, Roger Pau Monné wrote:
> On Tue, Jun 30, 2026 at 04:06:00PM +0200, Jan Beulich wrote:
>> --- a/xen/arch/x86/time.c
>> +++ b/xen/arch/x86/time.c
>> @@ -2660,6 +2660,7 @@ void __init early_time_init(void)
>>  
>>      set_time_scale(&t->tsc_scale, tmp);
>>      t->stamp.local_tsc = boot_tsc_stamp;
>> +    NOW_good = true;
> 
> Would you need a barrier here to ensure compiler doesn't re-order the
> writes?  Maybe using ACCESS_ONCE(), or a smp_wmb() like it's used in
> other arches?

Aiui it isn't needed here. The compiler can't re-order the two writes,
due to our use of -fno-strict-aliasing. The barrier is there on other
arch-es to avoid re-ordering in hardware.

Jan