netdev - Re: [PATCH v2] wifi: mac80211: do not abuse fq.lock in ieee80211_do

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Message-ID: <874jzemzrl.fsf@toke.dk>
Date:   Mon, 18 Jul 2022 13:22:22 +0200
From:   Toke Høiland-Jørgensen <toke@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Johannes Berg <johannes@...solutions.net>,
        Felix Fietkau <nbd@....name>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] wifi: mac80211: do not abuse fq.lock in
 ieee80211_do_stop()

Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> writes:

> lockdep complains use of uninitialized spinlock at ieee80211_do_stop() [1],
> for commit f856373e2f31ffd3 ("wifi: mac80211: do not wake queues on a vif
> that is being stopped") guards clear_bit() using fq.lock even before
> fq_init() from ieee80211_txq_setup_flows() initializes this spinlock.
>
> According to discussion [2], Toke was not happy with expanding usage of
> fq.lock. Since __ieee80211_wake_txqs() is called under RCU read lock, we
> can instead use synchronize_rcu() for flushing ieee80211_wake_txqs().

Ah, that's a neat solution! :)

Acked-by: Toke Høiland-Jørgensen <toke@...nel.org>