Re: [PATCH] cpu/hotplug: wait for cpuset_hotplug_work to finish on cpu onlining

[Peter Zijlstra]

On Thu, Feb 04, 2021 at 01:01:57AM +0000, Alexey Klimov wrote:
> @@ -1281,6 +1282,11 @@ static int cpu_up(unsigned int cpu, enum cpuhp_state target)
>  	err = _cpu_up(cpu, 0, target);
>  out:
>  	cpu_maps_update_done();
> +
> +	/* To avoid out of line uevent */
> +	if (!err)
> +		cpuset_wait_for_hotplug();
> +
>  	return err;
>  }
>  

> @@ -2071,14 +2075,18 @@ static void cpuhp_online_cpu_device(unsigned int cpu)
>  	struct device *dev = get_cpu_device(cpu);
>  
>  	dev->offline = false;
> -	/* Tell user space about the state change */
> -	kobject_uevent(&dev->kobj, KOBJ_ONLINE);
>  }
>  

One concequence of this is that you'll now get a bunch of notifications
across things like suspend/hybernate.