Re: [patch v3 18/36] [patch V2 18/38] cpu/hotplug: Add CPU state tracking and synchronization

[Thomas Gleixner]

On Tue, May 09 2023 at 13:07, Peter Zijlstra wrote:
> On Mon, May 08, 2023 at 09:43:55PM +0200, Thomas Gleixner wrote:
>
>> +static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
>> +{
>> +	atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
>> +	int sync = atomic_read(st);
>> +
>> +	while (!atomic_try_cmpxchg(st, &sync, state));
>> +}
>
> Why isn't:
>
> 	atomic_set(st, state);
>
> any good?

Good question. It's only the other side (control CPU) which needs to be
careful.

Thanks,

        tglx