netdev - Re: [PATCH net-next 1/2] net: sched: fix logic error in qdisc_run

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Message-ID: <871r4hi97m.fsf@toke.dk>
Date:   Tue, 19 Oct 2021 12:45:49 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "Ahmed S . Darwish" <a.darwish@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH net-next 1/2] net: sched: fix logic error in
 qdisc_run_begin()

Eric Dumazet <eric.dumazet@...il.com> writes:

> From: Eric Dumazet <edumazet@...gle.com>
>
> For non TCQ_F_NOLOCK qdisc, qdisc_run_begin() tries to set
> __QDISC_STATE_RUNNING and should return true if the bit was not set.
>
> test_and_set_bit() returns old bit value, therefore we need to invert.
>
> Fixes: 29cbcd858283 ("net: sched: Remove Qdisc::running sequence counter")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Ahmed S. Darwish <a.darwish@...utronix.de>
> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Ah! I had just finished bisecting that lockup on qdisc install and
figured I'd check the list before I started investigating further. And
indeed you had beaten me to the punch with a fix - thanks! :)

Tested-by: Toke Høiland-Jørgensen <toke@...hat.com>