Re: [Xen-devel] rcu_sched self-detect stall when disable vif device

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jan 27, 2015 at 04:03:52PM +0000, Julien Grall wrote:
> Hi,
> 
> While I'm working on support for 64K page in netfront, I got
> an rcu_sced self-detect message. It happens when netback is
> disabling the vif device due to an error.
> 
> I'm using Linux 3.19-rc5 on seattle (ARM64). Any idea why
> the processor is stucked in xenvif_rx_queue_purge?
> 

When you try to release a SKB, core network driver need to enter some
RCU cirital region to clean up. dst_release for one, calls call_rcu.

Wei.

> Here the log:
> 
> vif vif-20-0 vif20.0: txreq.offset: 3410, size: 342, end: 1382
> vif vif-20-0 vif20.0: fatal error; disabling device
> INFO: rcu_sched self-detected stall on CPU { 1}  (t=2101 jiffies g=37266 
> c=37265 q=2649)
> Task dump for CPU 1:
> vif20.0-q0-gues R  running task        0 12617      2 0x00000002
> Call trace:
> [<ffff800000089038>] dump_backtrace+0x0/0x124
> [<ffff80000008916c>] show_stack+0x10/0x1c
> [<ffff8000000bb1b4>] sched_show_task+0x98/0xf8
> [<ffff8000000bdca0>] dump_cpu_task+0x3c/0x4c
> [<ffff8000000d9fd4>] rcu_dump_cpu_stacks+0xa4/0xf8
> [<ffff8000000dd1a8>] rcu_check_callbacks+0x478/0x748
> [<ffff8000000e0b20>] update_process_times+0x38/0x6c
> [<ffff8000000eedd0>] tick_sched_timer+0x64/0x1b4
> [<ffff8000000e10a8>] __run_hrtimer+0x88/0x234
> [<ffff8000000e19c0>] hrtimer_interrupt+0x108/0x2b0
> [<ffff8000005934c4>] arch_timer_handler_virt+0x28/0x38
> [<ffff8000000d5e88>] handle_percpu_devid_irq+0x88/0x11c
> [<ffff8000000d1ec0>] generic_handle_irq+0x30/0x4c
> [<ffff8000000d21dc>] __handle_domain_irq+0x5c/0xac
> [<ffff8000000823b8>] gic_handle_irq+0x30/0x80
> Exception stack(0xffff800013a07c20 to 0xffff800013a07d40)
> 7c20: 058ed000 ffff0000 058ed9d8 ffff0000 13a07d60 ffff8000 0053c418 ffff8000
> 7c40: 00000000 00000000 0000ecf2 00000000 058ed9ec ffff0000 00000000 00000000
> 7c60: 00000001 00000000 00000000 00000000 00001800 00000000 feacbe9d 0000060d
> 7c80: 1ce5d6e0 ffff8000 13a07a90 ffff8000 00000400 00000000 ffffffff ffffffff
> 7ca0: 0013d000 00000000 00000090 00000000 00000040 00000000 9a272028 0000ffff
> 7cc0: 00099e64 ffff8000 00411010 00000000 df8fbb70 0000ffff 058ed000 ffff0000
> 7ce0: 058ed9d8 ffff0000 058ed000 ffff0000 058ed988 ffff0000 00956000 ffff8000
> 7d00: 19204840 ffff8000 000c75f8 ffff8000 13a04000 ffff8000 008a0598 ffff8000
> 7d20: 00000000 00000000 13a07d60 ffff8000 0053c3bc ffff8000 13a07d60 ffff8000
> [<ffff8000000854e4>] el1_irq+0x64/0xc0
> [<ffff80000053c448>] xenvif_rx_queue_purge+0x1c/0x30
> [<ffff80000053ea34>] xenvif_kthread_guest_rx+0x210/0x29c
> [<ffff8000000b1060>] kthread+0xd8/0xf0
> 
> 
> Regards,
> 
> -- 
> Julien Grall

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