| Subject: net/core/cpuhotplug: Drain input_pkt_queue lockless |
| From: Grygorii Strashko <grygorii.strashko@ti.com> |
| Date: Fri, 9 Oct 2015 09:25:49 -0500 |
| |
| 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 |
| [ 57.767552] CPU: 0 PID: 137 Comm: sh Not tainted 4.1.10-rt8-01700-g2c38702-dirty #55 |
| [ 57.767555] Hardware name: Generic DRA74X (Flattened Device Tree) |
| [ 57.767568] [<c001acd0>] (unwind_backtrace) from [<c001534c>] (show_stack+0x20/0x24) |
| [ 57.767579] [<c001534c>] (show_stack) from [<c075560c>] (dump_stack+0x84/0xa0) |
| [ 57.767593] [<c075560c>] (dump_stack) from [<c00aca48>] (spin_dump+0x84/0xac) |
| [ 57.767603] [<c00aca48>] (spin_dump) from [<c00acaa4>] (spin_bug+0x34/0x38) |
| [ 57.767614] [<c00acaa4>] (spin_bug) from [<c00acc10>] (do_raw_spin_lock+0x168/0x1c0) |
| [ 57.767624] [<c00acc10>] (do_raw_spin_lock) from [<c075b4cc>] (_raw_spin_lock+0x4c/0x54) |
| [ 57.767631] [<c075b4cc>] (_raw_spin_lock) from [<c07599fc>] (rt_spin_lock_slowlock+0x5c/0x374) |
| [ 57.767638] [<c07599fc>] (rt_spin_lock_slowlock) from [<c075bcf4>] (rt_spin_lock+0x38/0x70) |
| [ 57.767649] [<c075bcf4>] (rt_spin_lock) from [<c06333c0>] (skb_dequeue+0x28/0x7c) |
| [ 57.767662] [<c06333c0>] (skb_dequeue) from [<c06476ec>] (dev_cpu_callback+0x1b8/0x240) |
| [ 57.767673] [<c06476ec>] (dev_cpu_callback) from [<c007566c>] (notifier_call_chain+0x3c/0xb4) |
| |
| The reason is that skb_dequeue is taking skb->lock, but RT changed the |
| core code to use a raw spinlock. The non-raw lock is not initialized |
| on purpose to catch exactly this kind of problem. |
| |
| Fixes: 91df05da13a6 'net: Use skbufhead with raw lock' |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Cc: stable-rt@vger.kernel.org |
| --- |
| net/core/dev.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/net/core/dev.c |
| +++ b/net/core/dev.c |
| @@ -8022,7 +8022,7 @@ static int dev_cpu_callback(struct notif |
| 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))) { |
| netif_rx_ni(skb); |
| input_queue_head_incr(oldsd); |
| } |
