netdev - Re: [PATCH net-next 1/1] tipc: eliminate risk of double link

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Date:	Thu, 12 May 2016 17:12:02 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	jon.maloy@...csson.com
Cc:	netdev@...r.kernel.org, paul.gortmaker@...driver.com,
	parthasarathy.bhuvaragan@...csson.com, richard.alpe@...csson.com,
	ying.xue@...driver.com, maloy@...jonn.com,
	tipc-discussion@...ts.sourceforge.net
Subject: Re: [PATCH net-next 1/1] tipc: eliminate risk of double link_up
 events

From: Jon Maloy <jon.maloy@...csson.com>
Date: Wed, 11 May 2016 19:15:45 -0400

> When an ACTIVATE or data packet is received in a link in state
> ESTABLISHING, the link does not immediately change state to
> ESTABLISHED, but does instead return a LINK_UP event to the caller,
> which will execute the state change in a different lock context.
> 
> This non-atomic approach incurs a low risk that we may have two
> LINK_UP events pending simultaneously for the same link, resulting
> in the final part of the setup procedure being executed twice. The
> only potential harm caused by this it that we may see two LINK_UP
> events issued to subsribers of the topology server, something that
> may cause confusion.
> 
> This commit eliminates this risk by checking if the link is already
> up before proceeding with the second half of the setup.
> 
> Signed-off-by: Jon Maloy <jon.maloy@...csson.com>

Applied.