From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Felix Fietkau <nbd@nbd.name>, linux-wireless@vger.kernel.org
Cc:     johannes@sipsolutions.net
Subject: Re: [PATCH] mac80211: rework locking for txq scheduling / airtime fairness
In-Reply-To: <20190315100335.91445-1-nbd@nbd.name>
References: <20190315100335.91445-1-nbd@nbd.name>
Date:   Fri, 15 Mar 2019 14:04:49 +0100
Message-ID: <87zhpwwaoe.fsf@toke.dk>
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Sender: linux-wireless-owner@vger.kernel.org
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Felix Fietkau <nbd@nbd.name> writes:

> Holding the lock around the entire duration of tx scheduling can create
> some nasty lock contention, especially when processing airtime information
> from the tx status or the rx path.
> Improve locking by only holding the active_txq_lock for lookups / scheduling
> list modifications.
>
> Signed-off-by: Felix Fietkau <nbd@nbd.name>

Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>

>  include/net/mac80211.h | 49 ++++++++++++++++--------------------------
>  net/mac80211/tx.c      | 44 ++++++++++++++-----------------------
>  2 files changed, 35 insertions(+), 58 deletions(-)
>
> diff --git a/include/net/mac80211.h b/include/net/mac80211.h
> index 3771625b7a9d..0de0aba580eb 100644
> --- a/include/net/mac80211.h
> +++ b/include/net/mac80211.h

[ ... ]
> -void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)

> -	__acquires(txq_lock);
> +void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac);
> +
> +/* (deprecated) */
> +static inline void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
> +{
> +}

I figure I'll post a cleanup of this as part of my reworked schedule
change patch; since I'll be messing around with these bits anyway...

-Toke