From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: rcu_sched self-detect stall when disable vif device
Date: Tue, 27 Jan 2015 16:03:52 +0000
Message-ID: <54C7B6E8.9080106@linaro.org>
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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?

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