From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Cong Wang <xiyou.wangcong@gmail.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Rolf Neugebauer <rolf.neugebauer@docker.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
Justin Cormack <justin.cormack@docker.com>,
Ian Campbell <ian.campbell@docker.com>
Subject: Re: Long delays creating a netns after deleting one (possibly RCU related)
Date: Mon, 14 Nov 2016 18:29:37 +0100 [thread overview]
Message-ID: <1479144577.3734328.787380169.651B5477@webmail.messagingengine.com> (raw)
In-Reply-To: <CAM_iQpUDnPfVayQv7Q+ZtC_2_ZbX9MRX=514gFpF3E6XY+GtSA@mail.gmail.com>
Hi Cong,
On Sat, Nov 12, 2016, at 01:55, Cong Wang wrote:
> On Fri, Nov 11, 2016 at 4:23 PM, Paul E. McKenney
> <paulmck@linux.vnet.ibm.com> wrote:
> >
> > Ah! This net_mutex is different than RTNL. Should synchronize_net() be
> > modified to check for net_mutex being held in addition to the current
> > checks for RTNL being held?
> >
>
> Good point!
>
> Like commit be3fc413da9eb17cce0991f214ab0, checking
> for net_mutex for this case seems to be an optimization, I assume
> synchronize_rcu_expedited() and synchronize_rcu() have the same
> behavior...
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index eaad4c2..3415b6b 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -7762,7 +7762,7 @@ EXPORT_SYMBOL(free_netdev);
> void synchronize_net(void)
> {
> might_sleep();
> - if (rtnl_is_locked())
> + if (rtnl_is_locked() || lockdep_is_held(&net_mutex))
> synchronize_rcu_expedited();
I don't think we should depend on lockdep for this check but rather use
mutex_is_locked here (I think it would fail to build like this without
CONFIG_LOCKDEP).
Bye,
Hannes
prev parent reply other threads:[~2016-11-14 17:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-09 15:42 Long delays creating a netns after deleting one (possibly RCU related) Rolf Neugebauer
2016-11-10 17:37 ` Cong Wang
2016-11-10 21:24 ` Paul E. McKenney
2016-11-11 13:11 ` Rolf Neugebauer
2016-11-12 0:23 ` Paul E. McKenney
2016-11-12 0:55 ` Cong Wang
2016-11-14 6:47 ` Cong Wang
2016-11-14 16:24 ` Paul E. McKenney
2016-11-14 17:44 ` Cong Wang
2016-11-14 18:14 ` Paul E. McKenney
2016-11-14 22:12 ` Eric W. Biederman
2016-11-14 22:46 ` Eric Dumazet
2016-11-14 23:09 ` Eric Dumazet
2016-11-18 0:31 ` Jarno Rajahalme
2016-11-19 0:38 ` Jarno Rajahalme
2016-11-19 0:41 ` Eric Dumazet
2016-11-14 17:29 ` Hannes Frederic Sowa [this message]
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