net: disable preemption before call smp_processor_id()

xiaosuo · gregkh · commit 1378008ccdfd · 2010-08-26T16:46:00.000-07:00
[ 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 &lt;xiaosuo@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;
diff --git 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
 	{

Original file line number	Diff line number	Diff line change
`@@ -2504,6 +2504,7 @@ int netif_rx(struct sk_buff *skb)`
`2504`	`2504`	`struct rps_dev_flow voidflow, *rflow = &voidflow;`
`2505`	`2505`	`int cpu;`
`2506`	`2506`
	`2507`	`+ preempt_disable();`
`2507`	`2508`	`rcu_read_lock();`
`2508`	`2509`
`2509`	`2510`	`cpu = get_rps_cpu(skb->dev, skb, &rflow);`
`@@ -2513,6 +2514,7 @@ int netif_rx(struct sk_buff *skb)`
`2513`	`2514`	`ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);`
`2514`	`2515`
`2515`	`2516`	`rcu_read_unlock();`
	`2517`	`+ preempt_enable();`
`2516`	`2518`	`}`
`2517`	`2519`	`#else`
`2518`	`2520`	`{`