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From: Thomas Gleixner <tglx@kernel.org>
To: Qiliang Yuan <realwujing@gmail.com>, Ingo Molnar <mingo@redhat.com>,
 Peter Zijlstra <peterz@infradead.org>, Juri Lelli <juri.lelli@redhat.com>,
 Vincent Guittot <vincent.guittot@linaro.org>, Dietmar Eggemann
 <dietmar.eggemann@arm.com>, Steven Rostedt <rostedt@goodmis.org>, Ben
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 Uladzislau Rezki <urezki@gmail.com>, Mathieu Desnoyers
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 =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>, Jonathan Corbet
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 <skhan@linuxfoundation.org>, Shuah Khan <shuah@kernel.org>
Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org,
 cgroups@vger.kernel.org, linux-doc@vger.kernel.org,
 linux-kselftest@vger.kernel.org, Qiliang Yuan <realwujing@gmail.com>
Subject: Re: [PATCH v2 02/12] sched/isolation: Introduce housekeeping
 notifier infrastructure
In-Reply-To: <20260413-wujing-dhm-v2-2-06df21caba5d@gmail.com>
References: <20260413-wujing-dhm-v2-0-06df21caba5d@gmail.com>
 <20260413-wujing-dhm-v2-2-06df21caba5d@gmail.com>
Date: Tue, 14 Apr 2026 23:25:43 +0200
Message-ID: <87wly9dyjs.ffs@tglx>
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On Mon, Apr 13 2026 at 15:43, Qiliang Yuan wrote:
>  
> +int housekeeping_register_notifier(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&housekeeping_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(housekeeping_register_notifier);
> +
> +int housekeeping_unregister_notifier(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_unregister(&housekeeping_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(housekeeping_unregister_notifier);

As I said before, notifiers are a horrible interface especially for
things where most callers are built-in. Especially providing proper
ordering of the callbacks is a badly defined mechanism as demonstrated
by the now eliminated CPU hotplug notifiers.

> +int housekeeping_update_notify(enum hk_type type, const struct cpumask *new_mask)
> +{
> +	struct housekeeping_update update = {
> +		.type = type,
> +		.new_mask = new_mask,
> +	};
> +
> +	return blocking_notifier_call_chain(&housekeeping_notifier_list, HK_UPDATE_MASK, &update);
> +}
> +EXPORT_SYMBOL_GPL(housekeeping_update_notify);

Why is this exported? Are random modules allowed to invoke this?