netdev - Re: Soft lockup in inet_put

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Message-ID: <1482201702.1521.13.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 19 Dec 2016 18:41:42 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Tom Herbert <tom@...bertland.com>
Cc:     David Miller <davem@...emloft.net>, Josef Bacik <jbacik@...com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Craig Gallek <kraigatgoog@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: Soft lockup in inet_put_port on 4.6

On Mon, 2016-12-19 at 18:07 -0800, Tom Herbert wrote:

> When sockets created SO_REUSEPORT move to TW state they are placed
> back on the the tb->owners. fastreuse port is no longer set so we have
> to walk potential long list of sockets in tb->owners to open a new
> listener socket. I imagine this is happens when we try to open a new
> listener SO_REUSEPORT after the system has been running a while and so
> we hit the long tb->owners list.

Hmm...  __inet_twsk_hashdance() does not change tb->fastreuse

So where tb->fastreuse is cleared ?

If all your sockets have SO_REUSEPORT set, this should not happen.