From: Eric Dumazet <edumazet@google.com>
To: Francesco Ruggeri <fruggeri@arista.com>
Cc: open list <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
Cong Wang <xiyou.wangcong@gmail.com>,
Taehee Yoo <ap420073@gmail.com>, Andrii Nakryiko <andriin@fb.com>,
Jiri Pirko <jiri@mellanox.com>,
Alexei Starovoitov <ast@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
David Miller <davem@davemloft.net>
Subject: Re: [PATCH] net: make netdev_wait_allrefs wake-able
Date: Thu, 17 Sep 2020 08:51:45 +0200 [thread overview]
Message-ID: <CANn89iJOO9cbOqCNpRK4OrZy-L6P8aJJcPMjs5=RHF=fsjEe2Q@mail.gmail.com> (raw)
In-Reply-To: <CA+HUmGjX4_4_UXWNn=EehQ_3QtFPZq8RJU146r-nc0nA8apx7w@mail.gmail.com>
On Thu, Sep 17, 2020 at 8:33 AM Francesco Ruggeri <fruggeri@arista.com> wrote:
>
> > static inline void dev_put(struct net_device *dev)
> > {
> > + struct task_struct *destroy_task = dev->destroy_task;
> > +
> > this_cpu_dec(*dev->pcpu_refcnt);
> > + if (destroy_task)
> > + wake_up_process(destroy_task);
> > }
>
> I just realized that this introduces a race, if dev_put drops the last
> reference, an already running netdev_wait_allrefs runs to completion
> and then dev_put tries to wake it up.
> Any suggestions on how to avoid this without resorting to
> locking?
>
Honestly I would not touch dev_put() at all.
Simply change the msleep(250) to something better, with maybe
exponential backoff.
next prev parent reply other threads:[~2020-09-17 6:52 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 2:00 [PATCH] net: make netdev_wait_allrefs wake-able Francesco Ruggeri
2020-09-17 6:33 ` Francesco Ruggeri
2020-09-17 6:51 ` Eric Dumazet [this message]
2020-09-17 16:17 ` Francesco Ruggeri
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