linux-kernel - [071/114] net: disable preemption before call smp_processor

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Date:	Tue, 24 Aug 2010 15:45:16 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Changli Gao <xiaosuo@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [071/114] net: disable preemption before call smp_processor_id()

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------


From: Changli Gao <xiaosuo@...il.com>

[ Upstream commit cece1945bffcf1a823cdfa36669beae118419351 ]

Although netif_rx() isn't expected to be called in process context with
preemption enabled, it'd better handle this case. And this is why get_cpu()
is used in the non-RPS #ifdef branch. If tree RCU is selected,
rcu_read_lock() won't disable preemption, so preempt_disable() should be
called explictly.

Signed-off-by: Changli Gao <xiaosuo@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 net/core/dev.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2504,6 +2504,7 @@ int netif_rx(struct sk_buff *skb)
 		struct rps_dev_flow voidflow, *rflow = &voidflow;
 		int cpu;
 
+		preempt_disable();
 		rcu_read_lock();
 
 		cpu = get_rps_cpu(skb->dev, skb, &rflow);
@@ -2513,6 +2514,7 @@ int netif_rx(struct sk_buff *skb)
 		ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
 
 		rcu_read_unlock();
+		preempt_enable();
 	}
 #else
 	{


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