netdev - Re: Long delays creating a netns after deleting one (possibly RCU related)

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Message-ID: <1479163571.8455.83.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 14 Nov 2016 14:46:11 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Rolf Neugebauer <rolf.neugebauer@...ker.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Justin Cormack <justin.cormack@...ker.com>,
        Ian Campbell <ian.campbell@...ker.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: Long delays creating a netns after deleting one (possibly RCU
 related)

On Mon, 2016-11-14 at 16:12 -0600, Eric W. Biederman wrote:

> synchronize_rcu_expidited is not enough if you have multiple network
> devices in play.
> 
> Looking at the code it comes down to this commit, and it appears there
> is a promise add rcu grace period combining by Eric Dumazet.
> 
> Eric since people are hitting noticable stalls because of the rcu grace
> period taking a long time do you think you could look at this code path
> a bit more?
> 
> commit 93d05d4a320cb16712bb3d57a9658f395d8cecb9
> Author: Eric Dumazet <edumazet@...gle.com>
> Date:   Wed Nov 18 06:31:03 2015 -0800

Absolutely, I will take a loop asap.

Thanks Eric.