netdev - Re: [PATCH v2 net] net: rps: fix cpu unplug

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Message-Id: <20150116.010532.827422113288970815.davem@davemloft.net>
Date:	Fri, 16 Jan 2015 01:05:32 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	subashab@...eaurora.org, psodagud@...eaurora.org,
	netdev@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH v2 net] net: rps: fix cpu unplug

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 15 Jan 2015 17:04:22 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> softnet_data.input_pkt_queue is protected by a spinlock that
> we must hold when transferring packets from victim queue to an active
> one. This is because other cpus could still be trying to enqueue packets
> into victim queue.
> 
> A second problem is that when we transfert the NAPI poll_list from
> victim to current cpu, we absolutely need to special case the percpu
> backlog, because we do not want to add complex locking to protect
> process_queue : Only owner cpu is allowed to manipulate it, unless cpu
> is offline.
> 
> Based on initial patch from Prasad Sodagudi & Subash Abhinov
> Kasiviswanathan.
> 
> This version is better because we do not slow down packet processing,
> only make migration safer.
> 
> Reported-by: Prasad Sodagudi <psodagud@...eaurora.org>
> Reported-by: Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable, thanks Eric.
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