netdev - Re: sctp: hang in sctp_remaddr_seq

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Message-ID: <1363620340.29475.132.camel@edumazet-glaptop>
Date:	Mon, 18 Mar 2013 08:25:40 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Sasha Levin <sasha.levin@...cle.com>, vyasevich@...il.com,
	sri@...ibm.com, "David S. Miller" <davem@...emloft.net>,
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	Dave Jones <davej@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: sctp: hang in sctp_remaddr_seq_show

On Mon, 2013-03-18 at 07:04 -0400, Neil Horman wrote:

> I'm not sure why the process would never get back to the schedule, but looking
> at the sctp_remaddr_seq_show function, I think that we should convert this
> sequence:
> 	sctp_local_bh_disable();
> 	read_lock(&head->lock);
> 	rcu_read_lock();
> 
> to this:
> 	read_lock(&head->lock);
> 	rcu_read_lock_bh();
> 
> Neil

I dont think so.

BH needs to be disabled before read_lock(&head->lock);

or else, write_lock() could deadlock (assuming it can be called from BH)


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