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From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: David Ahern <dsahern@gmail.com>,
	syzbot 
	<bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	syzkaller-bugs@googlegroups.com,
	David Miller <davem@davemloft.net>,
	Florian Westphal <fw@strlen.de>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Xin Long <lucien.xin@gmail.com>,
	jakub.kicinski@netronome.com, mschiffer@universe-factory.net,
	Vladislav Yasevich <vyasevich@gmail.com>,
	Jiri Benc <jbenc@redhat.com>, netdev <netdev@vger.kernel.org>,
	Neil Horman <nhorman@tuxdriver.com>,
	linux-sctp@vger.kernel.org
Subject: Re: INFO: task hung in bpf_exit_net
Date: Fri, 22 Dec 2017 16:28:07 -0200	[thread overview]
Message-ID: <20171222182807.GC32765@localhost.localdomain> (raw)
In-Reply-To: <CACT4Y+aaSX4S3KHJjqkiQhhOZAtEN_fMD1m_Ve3rz4u4x9KSWg@mail.gmail.com>

On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
...
> > Same with this one, perhaps related to / fixed by:
> >     http://patchwork.ozlabs.org/patch/850957/
> >
> 
> 
> 
> Looking at the log, this one seems to be an infinite loop in SCTP code
> with console output in it. Kernel is busy printing gazilion of:
> 
> [  176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> ** 110 printk messages dropped **
> [  176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> ** 103 printk messages dropped **
> ...
> [  246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> [  246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> [  246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> low, using default minimum of 512
> 
> Looks like a different issue.
> 

Oh. I guess this is caused by the interface having a MTU smaller than
SCTP_DEFAULT_MINSEGMENT (512), as the icmp frag needed handler
(sctp_icmp_frag_needed) will trigger an instant retransmission.
But as the MTU is smaller, SCTP won't update it, but will issue the
retransmission anyway.

I will test this soon. Should be fairly easy to trigger it.

  Marcelo

  parent reply	other threads:[~2017-12-22 18:28 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <001a1143fd00a8cc790560b0b552@google.com>
2017-12-19 12:47 ` INFO: task hung in bpf_exit_net Dmitry Vyukov
2017-12-19 16:21   ` Xin Long
2017-12-19 18:20   ` David Ahern
2017-12-22 10:58     ` Dmitry Vyukov
2017-12-22 11:16       ` Marcelo Ricardo Leitner
2017-12-22 11:24         ` Dmitry Vyukov
2017-12-22 18:28       ` Marcelo Ricardo Leitner [this message]
2017-12-22 19:04         ` Marcelo Ricardo Leitner
2018-02-02 23:39           ` Eric Biggers

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