On 10/12/2015 11:16 AM, Thomas Gleixner wrote:

On Fri, 9 Oct 2015, Grygorii Strashko wrote:

quoted

I can constantly see below error report with 4.1 RT-kernel on TI ARM dra7-evm
if I'm trying to unplug cpu1:

[   57.737589] CPU1: shutdown
[   57.767537] BUG: spinlock bad magic on CPU#0, sh/137
[   57.767546]  lock: 0xee994730, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0

quoted

It looks like this backtrace was introduces by

commit 91df05da13a6c6c358e71182e80f19f3c48d1615
net: Use skbufhead with raw lock

I see the potential fix for this issue as below:

index 4969c0d..f8c23de 100644

--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -7217,7 +7217,7 @@ static int dev_cpu_callback(struct notifier_block *nfb,
                 netif_rx_ni(skb);
                 input_queue_head_incr(oldsd);
         }
-       while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) {
+       while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {

Your patch is white space damaged ....

quoted

                 netif_rx_ni(skb);
                 input_queue_head_incr(oldsd);
         }

input_pkt_queue is per-cpu queue and at this moment cpu is dead already,
so no one should touch it. But I'm not sure if my assumption is correct.

It is. Picking it up for the next release

Thanks & Sorry. I've not expected this diff/hack to be applied as patch :(

-- 
regards,
-grygorii