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Subject: Re: [PATCH] wifi: ath11k: fix RCU documentation in
 ath11k_mac_op_ipv6_changed()
From: Kalle Valo <kvalo@kernel.org>
In-Reply-To: <20240531022411.6543-1-quic_bqiang@quicinc.com>
References: <20240531022411.6543-1-quic_bqiang@quicinc.com>
To: Baochen Qiang <quic_bqiang@quicinc.com>
Cc: <ath11k@lists.infradead.org>, <linux-wireless@vger.kernel.org>,
 <quic_bqiang@quicinc.com>
User-Agent: pwcli/0.1.1-git (https://github.com/kvalo/pwcli/) Python/3.11.2
Message-ID: <171813121489.3564613.14982279115447611746.kvalo@kernel.org>
Date: Tue, 11 Jun 2024 18:40:16 +0000 (UTC)

Baochen Qiang <quic_bqiang@quicinc.com> wrote:

> Current documentation on RCU in ath11k_mac_op_ipv6_changed() says:
> 
>         /* Note: read_lock_bh() calls rcu_read_lock() */
>         read_lock_bh(&idev->lock);
> 
> This is wrong because without enabling CONFIG_PREEMPT_RT
> rcu_read_lock() is not called by read_lock_bh(). The reason
> why current code works even in a CONFIG_PREEMPT_RT=n kernel
> is because atomic_notifier_call_chain() already does that for
> us, see:
> 
>         int atomic_notifier_call_chain()
>         {
>                 ...
>                 rcu_read_lock();
>                 ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
>                 rcu_read_unlock();
>                 ...
>         }
> 
> and backtrace:
> 
>         ath11k_mac_op_ipv6_changed
>         ieee80211_ifa6_changed
>         notifier_call_chain
>         atomic_notifier_call_chain
> 
> So update the comment to make it correct.
> 
> This is found during code review, compile tested only.
> 
> Fixes: feafe59c8975 ("wifi: ath11k: use RCU when accessing struct inet6_dev::ac_list")
> Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
> Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
> Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>

Patch applied to ath-next branch of ath.git, thanks.

53d7c99719e2 wifi: ath11k: fix RCU documentation in ath11k_mac_op_ipv6_changed()

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20240531022411.6543-1-quic_bqiang@quicinc.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches