From: Kalle Valo <kvalo@kernel.org>
To: Baochen Qiang <quic_bqiang@quicinc.com>
Cc: <ath12k@lists.infradead.org>,  <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH 1/8] wifi: ath12k: Add MLO station state change handling
References: <20241106142617.660901-1-kvalo@kernel.org>
	<20241106142617.660901-2-kvalo@kernel.org>
	<f75d7222-514b-4c6f-985d-e6ffd67e317a@quicinc.com>
	<877c984eym.fsf@kernel.org>
	<ffa411d1-89d3-4278-9f62-828c27c0afe0@quicinc.com>
Date: Wed, 20 Nov 2024 17:57:07 +0200
In-Reply-To: <ffa411d1-89d3-4278-9f62-828c27c0afe0@quicinc.com> (Baochen
	Qiang's message of "Wed, 13 Nov 2024 10:33:38 +0800")
Message-ID: <87frnlzyng.fsf@kernel.org>
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Baochen Qiang <quic_bqiang@quicinc.com> writes:

>>>> +	arsta->arvif = arvif;
>>>> +	arsta->ahsta = ahsta;
>>>> +	arsta->state = IEEE80211_STA_NONE;
>>>> +	wiphy_work_init(&arsta->update_wk, ath12k_sta_rc_update_wk);
>>>> +
>>>> +	rcu_assign_pointer(ahsta->link[link_id], arsta);
>>>> +
>>>> +	synchronize_rcu();
>>>
>>> what are we waiting for here?
>> 
>> That's a good question. I didn't analyse that thoroughly but I'm just
>> making sure here that all readers have access to the new arsta before we
>> return to mac80211.
>
> why would readers have to access arsta BEFORE returning to mac80211?
> any potential race conditions?
>
> and even if it is necessary, how could synchronize_rcu() guarantee
> that? synchronize_rcu() is used to make sure all readers have exited
> from RCU read critical section, I don;t see how it could make sure a
> newly assigned entry get accessed.

Yeah, I'm not making any sense. I'll remove synchronize_rcu() in v2.

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