Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 4 Feb 2021 10:46:10 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Alexey Klimov <aklimov@redhat.com>
Cc:     linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        yury.norov@gmail.com, daniel.m.jordan@oracle.com,
        tglx@linutronix.de, jobaker@redhat.com, audralmitchel@gmail.com,
        arnd@arndb.de, gregkh@linuxfoundation.org, rafael@kernel.org,
        tj@kernel.org, lizefan@huawei.com, qais.yousef@arm.com,
        hannes@cmpxchg.org, klimov.linux@gmail.com
Subject: Re: [PATCH] cpu/hotplug: wait for cpuset_hotplug_work to finish on
 cpu onlining
Message-ID: <YBvCYhdPai+pb8u2@hirez.programming.kicks-ass.net>
References: <20210204010157.1823669-1-aklimov@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210204010157.1823669-1-aklimov@redhat.com>
Precedence: bulk

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.