netdev - Re: [PATCH] sctp: Add RCU protection to assoc->transport_addr

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Message-ID: <20121206190835.GF16122@casper.infradead.org>
Date:	Thu, 6 Dec 2012 19:08:35 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH] sctp: Add RCU protection to assoc->transport_addr_list

On 12/06/12 at 01:57pm, Vlad Yasevich wrote:
> On 12/06/2012 01:44 PM, Thomas Graf wrote:
> >On 12/06/12 at 01:35pm, Vlad Yasevich wrote:
> >>We may want to mark transports as dead sooner.  Probably right about
> >>the time we pull them off the list.
> >
> >We mark it dead in sctp_transport_free() which is called at the
> >end of sctp_assoc_rm_peer(). Do you want to mark it dead at the
> >beginning of sctp_assoc_rm_peer() as well? (We still need to
> >mark in sctp_transport_free() anyway).
> 
> Crud..  sctp_transport_free() is called directly in places...   Hmm...
> the one in sctp_association_free() may need to be list_del_rcu()...

It's not really needed but it wouldn't be wrong from a
documentation perspective. The assoc is always unhashed
while holding head->lock before sctp_association_free()
and all current RCU readers of transport_addr_list access
the the assoc while holding a read-lock on head->lock.

Let me respin this patch and do a list_del_rcu() there
to document the RCU'iness of it.
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