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Date: Thu, 8 Sep 2016 10:04:04 +0800
From: Ye Xiaolong <xiaolong.ye@intel.com>
To: Jens Axboe <axboe@fb.com>, Tejun Heo <tj@kernel.org>,
        Fengguang Wu <fengguang.wu@intel.com>
Cc: lkp@01.org, Philip Li <philip.li@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [LKP] [writeback] 8bc4ad9498: INFO: suspicious RCU usage. ]
Message-ID: <20160908020404.GA12960@yexl-desktop>
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On 09/08, Fengguang Wu wrote:
>Hi Jens and Tejun,
>
>>The command line was in the original email:
>>
>>$ qemu-system-x86_64 -enable-kvm -cpu Westmere -m 512M
>>
>>And agree, in general it'd be nice if there was a link to the image as
>>well, so that folks can reproduce.
>
>Yes we have a reproduce script internally, however need to polish it
>up and make it general usable by kernel developers.
>
>CC Philip. It'd be helpful to give more priority to the "lkp qemu"
>reproduce command.
>
>For the warning here, it does not depend on any initrd, I just
>confirmed this simple script can reproduce the problem.

Yes, just confirmed that v4.8-rc5 doesn't have this warning, while kernel
for the updated commit (fa0e2cb1af765691fabd329f03cad563a0eebf18) on branch 
wb-buf-throttle could reproduce it.

Thanks,
Xiaolong
>
>-----------------------------------------------------------------------------
>#!/bin/bash
>
>kernel=$1
>
>kvm=(
>       qemu-system-x86_64
>       -enable-kvm
>       -cpu Westmere
>       -kernel $kernel
>       -m 1024
>       -smp 1
>       -device e1000,netdev=net0
>       -netdev user,id=net0
>       -boot order=nc
>       -no-reboot
>       -watchdog i6300esb
>       -watchdog-action debug
>       -rtc base=localtime
>       -nographic
>)
>
>
>append=(
>       ip=::::vm-kbuild-yocto-ia32-17::dhcp
>       root=/dev/ram0
>       debug
>       apic=debug
>       sysrq_always_enabled
>       rcupdate.rcu_cpu_stall_timeout=100
>       net.ifnames=0
>       printk.devkmsg=on
>       panic=-1
>       softlockup_panic=1
>       nmi_watchdog=panic
>       oops=panic
>       load_ramdisk=2
>       prompt_ramdisk=0
>       systemd.log_level=err
>       ignore_loglevel
>       earlyprintk=ttyS0,115200
>       console=ttyS0,115200
>       console=tty0
>       vga=normal
>       rw
>)
>
>"${kvm[@]}" -append "${append[*]}"
>-----------------------------------------------------------------------------
>
>Thanks,
>Fengguang