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Date:	Mon, 16 Feb 2015 11:30:38 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	LKP <lkp@...org>, linux-kernel@...r.kernel.org
Subject: Re: [torture] INFO: task killall5:262 blocked for more than 120
 seconds.

On Mon, Feb 16, 2015 at 03:25:28PM +0800, Fengguang Wu wrote:
> Hi Paul,
> 
> FYI, this may be very hard to reproduce.

Indeed, I have not seen it.

But was this on a CONFIG_PREEMPT=n kernel?

							Thanx, Paul

> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git revert-d347efeb16d3d5150cb7f8d50b05f388b572840e-ab7d45053f99f44f81a221eb5c9fbe253ee94524
> 
> commit ab7d45053f99f44f81a221eb5c9fbe253ee94524
> Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> AuthorDate: Tue Mar 4 11:03:21 2014 -0800
> Commit:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> CommitDate: Wed May 14 09:46:02 2014 -0700
> 
>     torture: Increase stutter-end intensity
>     
>     Currently, all stuttered kthreads block a jiffy at a time, which can
>     result in them starting at different times.  (Note: This is not an
>     energy-efficiency problem unless you run torture tests in production,
>     in which case you have other problems!)  This commit increases the
>     intensity of the restart event by causing kthreads to spin through the
>     last jiffy, restarting when they see the variable change.
>     
>     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>     Reviewed-by: Josh Triplett <josh@...htriplett.org>
> 
> +---------------------------------------------------------------+------------+------------+------------+
> |                                                               | fff35c4e9f | ab7d45053f | 7afb8886a0 |
> +---------------------------------------------------------------+------------+------------+------------+
> | boot_successes                                                | 1000       | 884        | 14         |
> | boot_failures                                                 | 0          | 16         | 2          |
> | INFO:task_blocked_for_more_than#seconds                       | 0          | 12         | 2          |
> | Kernel_panic-not_syncing:hung_task:blocked_tasks              | 0          | 12         | 2          |
> | backtrace:watchdog                                            | 0          | 12         | 2          |
> | WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_stats_print() | 0          | 4          |            |
> | backtrace:rcu_torture_stats                                   | 0          | 4          |            |
> | backtrace:rcu_torture_boost                                   | 0          | 0          | 2          |
> +---------------------------------------------------------------+------------+------------+------------+
> 
> [  183.290093] rcu-torture: Reader Batch:  7006877 238 0 0 0 0 0 0 0 0 0
> [  183.290093] rcu-torture: Free-Block Circulation:  622 622 621 620 619 618 617 616 615 614 0
> [  183.290093] ??? Writer stall state 5 g550 c550 f0x0
> [  240.530125] INFO: task killall5:262 blocked for more than 120 seconds.
> [  240.531833]       Not tainted 3.15.0-rc1-00022-gab7d450 #5
> [  240.550103] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [  240.551948] CPU: 0 PID: 27 Comm: khungtaskd Not tainted 3.15.0-rc1-00022-gab7d450 #5
> [  240.553610] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [  240.555632] task: d1cea290 ti: d1d3e000 task.ti: d1d3e000
> [  240.556741] Stack:
> [  240.557395] Call Trace:
> [  240.558122] Code: 81 00 d3 ff ff f6 c4 10 75 ed c1 e3 18 89 99 10 d3 ff ff 89 f0 09 d0 80 ce 04 83 fe 02 0f 45 d0 a1 6c 1b 06 c2 89 90 00 d3 ff ff <89> f8 50 9d 8d 74 26 00 83 c4 04 5b 5e 5f 5d c3 ba 70 00 00 00
> [  240.560012] CPU: 1 PID: 64 Comm: rcu_torture_boo Not tainted 3.15.0-rc1-00022-gab7d450 #5
> [  240.560012] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [  240.560012] task: cc4d4310 ti: cc4d8000 task.ti: cc4d8000
> [  240.560012] Stack:
> [  240.560012] Call Trace:
> [  240.560012] Code: 00 00 8b 00 85 c0 0f 85 85 00 00 00 a1 fc 85 7c c2 85 c0 74 46 a1 fc 85 7c c2 83 f8 01 74 5c a1 fc 85 7c c2 85 c0 74 23 8d 76 00 <31> c9 ba 1c 02 00 00 b8 ac d5 eb c1 e8 5f 12 fb ff e8 8a 0c b3
> [  240.598110] Kernel panic - not syncing: hung_task: blocked tasks
> [  240.599315] CPU: 0 PID: 27 Comm: khungtaskd Not tainted 3.15.0-rc1-00022-gab7d450 #5
> [  240.600854] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [  240.602788]  00007f95 00000000 d1d3fedc c1be7294 d29b6f60 d1d3fef4 c1be4f9d 00007f95
> [  240.604992]  d29b6f60 00007f95 d29b71c8 d1d3ff24 c10a7d1d c1eb744c 00000395 00000078
> [  240.607268]  00000002 00007f95 d29b6f60 d29b71c8 d1d38e00 00000000 c10a7a50 d1d3ffac
> [  240.607938] Call Trace:
> [  240.607938]  [<c1be7294>] dump_stack+0x48/0x69
> [  240.607938]  [<c1be4f9d>] panic+0x7c/0x184
> [  240.607938]  [<c10a7d1d>] watchdog+0x2cd/0x2d0
> [  240.607938]  [<c10a7a50>] ? hung_task_panic+0x20/0x20
> [  240.607938]  [<c105fb93>] kthread+0xa3/0xc0
> [  240.607938]  [<c1bf0701>] ret_from_kernel_thread+0x21/0x30
> [  240.607938]  [<c105faf0>] ? __kthread_unpark+0x50/0x50
> [  240.607938] Kernel Offset: 0x0 from 0xc1000000 (relocation range: 0xc0000000-0xd47dffff)
> 
> Elapsed time: 240
> 
> git bisect start v3.16 v3.15 --
> git bisect  bad 5170a3b24a9141e2349a3420448743b7c68f2223  # 06:12      0-     11  Merge branch 'akpm' (patches from Andrew Morton)
> git bisect  bad 1ad96bb0a20fa26b952b2250e89d14b6397bf618  # 06:12      0-     17  Merge tag 'gpio-v3.16-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio
> git bisect  bad 412dd3a6daf0cadce1b2d6a34fa3713f40255579  # 06:12      0-     46  Merge tag 'xfs-for-linus-3.16-rc1' of git://oss.sgi.com/xfs/xfs
> git bisect  bad b1cce8032f6abe900b078d24f3c3938726528f97  # 06:20    281-      7  Merge branch 'for-next' of git://git.samba.org/sfrench/cifs-2.6
> git bisect  bad da85d191f58a44e149a7c07dbae78b3042909798  # 06:36    416-      7  Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
> git bisect  bad f8409abdc592e13cefbe4e4a24a84b3d5741e85f  # 07:00    500-     13  Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
> git bisect  bad ed81e780a7dd5698a986f246fad6a1d8d0b6f9ce  # 07:17    680-     14  Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
> git bisect  bad 3f17ea6dea8ba5668873afa54628a91aaa3fb1c0  # 07:32    772-     10  Merge branch 'next' (accumulated 3.16 merge window patches) into master
> git bisect good 49eb7b0750d9483c74e9c14ae6ea1e9d62481c3c  # 07:54    900+      6  Merge tag 'tty-3.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty into next
> git bisect  bad 15b588303155b22edd559672905db8e59a44ef9a  # 08:07    625-     13  Merge tag 'fbdev-omap-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux into next
> git bisect  bad 776edb59317ada867dfcddde40b55648beeb0078  # 08:29    562-     12  Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next
> git bisect good f456205265a61f1d649f8378eceaa163850cba4e  # 08:46    900+      2  Merge tag 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging into next
> git bisect good e13cccfd86481bd4c0499577f44c570d334da79b  # 08:59    900+      2  Merge tag 'spi-v3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi into next
> git bisect good ff806d034ef8e9a95ff0b0532104dd65332e446b  # 09:15    900+      0  Merge branch 'for-v3.16' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping into next
> git bisect  bad 6348675c4e3612e001860354fea78258e041d9a1  # 09:32    550-      8  torture: Remove unused definition
> git bisect  bad ab7d45053f99f44f81a221eb5c9fbe253ee94524  # 09:40    438-      8  torture: Increase stutter-end intensity
> git bisect good a0edd47ca4f0ffa33df137c13a08189bae66bcc3  # 09:59    900+      4  torture: Rename RCU_QEMU_INTERACTIVE to TORTURE_QEMU_INTERACTIVE
> git bisect good b3b8a4d42bba8e1fb1b91cc6fd53829d28a503de  # 10:13    900+      4  rcutorture: Mark function as static in kernel/rcu/torture.c
> git bisect good 589a8f59509dc4c68f9c1e2522c5b0b556009221  # 10:38    900+      2  rcutorture: Print negatives for SRCU counter wraparound
> git bisect good fff35c4e9fbb0982aef6230cbf713c2492925eca  # 10:55    900+      0  torture: Report diagnostics from qemu
> # first bad commit: [ab7d45053f99f44f81a221eb5c9fbe253ee94524] torture: Increase stutter-end intensity
> git bisect good fff35c4e9fbb0982aef6230cbf713c2492925eca  # 10:57   1000+      0  torture: Report diagnostics from qemu
> # extra tests with DEBUG_INFO
> # extra tests on HEAD of net/master
> git bisect  bad 7afb8886a05be68e376655539a064ec672de8a8e  # 11:02      0-      2  rtnetlink: call ->dellink on failure when ->newlink exists
> # extra tests on tree/branch linus/master
> # extra tests with first bad commit reverted
> # extra tests on tree/branch linus/master
> # extra tests on tree/branch next/master
> 
> 
> This script may reproduce the error.
> 
> ----------------------------------------------------------------------------
> #!/bin/bash
> 
> kernel=$1
> initrd=quantal-core-i386.cgz
> 
> wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
> 
> kvm=(
> 	qemu-system-x86_64
> 	-cpu kvm64
> 	-enable-kvm
> 	-kernel $kernel
> 	-initrd $initrd
> 	-m 320
> 	-smp 2
> 	-net nic,vlan=1,model=e1000
> 	-net user,vlan=1
> 	-boot order=nc
> 	-no-reboot
> 	-watchdog i6300esb
> 	-rtc base=localtime
> 	-serial stdio
> 	-display none
> 	-monitor null 
> )
> 
> append=(
> 	hung_task_panic=1
> 	earlyprintk=ttyS0,115200
> 	rd.udev.log-priority=err
> 	systemd.log_target=journal
> 	systemd.log_level=warning
> 	debug
> 	apic=debug
> 	sysrq_always_enabled
> 	rcupdate.rcu_cpu_stall_timeout=100
> 	panic=-1
> 	softlockup_panic=1
> 	nmi_watchdog=panic
> 	oops=panic
> 	load_ramdisk=2
> 	prompt_ramdisk=0
> 	console=ttyS0,115200
> 	console=tty0
> 	vga=normal
> 	root=/dev/ram0
> 	rw
> 	drbd.minor_count=8
> )
> 
> "${kvm[@]}" --append "${append[*]}"
> ----------------------------------------------------------------------------
> 
> Thanks,
> Fengguang
> 

--
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