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Message-ID: <538FF977.50805@intel.com>
Date:	Thu, 05 Jun 2014 13:00:39 +0800
From:	Jet Chen <jet.chen@...el.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
CC:	Fengguang Wu <fengguang.wu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Yuanhan Liu <yuanhan.liu@...el.com>
Subject: [rcu] BUG: unable to handle kernel NULL pointer dereference at  (null)

Hi Paul,

0day kernel testing robot got the below dmesg and the first bad commit is

git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/dev
commit a558e309f99cf8b809691417324c6770e10bb614
Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
AuthorDate: Wed Jun 4 13:46:03 2014 -0700
Commit:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
CommitDate: Wed Jun 4 15:07:01 2014 -0700

     rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs
         Binding the grace-period kthreads to the timekeeping CPU resulted in
     significant performance decreases for some workloads.  For more detail,
     see:
         https://lkml.org/lkml/2014/6/3/395 for benchmark numbers
         https://lkml.org/lkml/2014/6/4/218 for CPU statistics
         This commit avoids this issue for many configurations by binding the
     grace-period kthreads to all the non-NO_HZ_FULL CPUs, not just to the
     sole timekeeping CPU.
         Reported-by: Jet Chen <jet.chen@...el.com>
     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

+------------------------------------------------------+------------+------------+
|                                                      | b5ec6ac529 | a558e309f9 |
+------------------------------------------------------+------------+------------+
| boot_successes                                       | 78         | 0          |
| boot_failures                                        | 2          | 30         |
| BUG:kernel_test_crashed                              | 2          |            |
| BUG:unable_to_handle_kernel_NULL_pointer_dereference | 0          | 29         |
| Oops                                                 | 0          | 30         |
| RIP:__bitmap_equal                                   | 0          | 30         |
| Kernel_panic-not_syncing:Fatal_exception             | 0          | 30         |
| backtrace:set_cpus_allowed_ptr                       | 0          | 30         |
+------------------------------------------------------+------------+------------+

[    0.252885] pci 0000:00:02.0: Boot video device
[    0.253561] PCI: CLS 0 bytes, default 64
[    0.254253] Unpacking initramfs...
[    0.254266] BUG: unable to handle kernel NULL pointer dereference at           (null)
[    0.254289] IP: [<ffffffff813d93c1>] __bitmap_equal+0x51/0x90
[    0.254290] PGD 0 [    0.254291] Oops: 0000 [#1] SMP [    0.254294] Modules linked in:
[    0.254300] CPU: 1 PID: 7 Comm: rcu_sched Not tainted 3.15.0-rc1-00084-ga558e30 #1
[    0.254300] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    0.254301] task: ffff880013783b00 ti: ffff880013788000 task.ti: ffff880013788000
[    0.254303] RIP: 0010:[<ffffffff813d93c1>]  [<ffffffff813d93c1>] __bitmap_equal+0x51/0x90
[    0.254306] RSP: 0000:ffff880013789dd0  EFLAGS: 00010046
[    0.254306] RAX: 0000000000000000 RBX: ffff880013783b00 RCX: 0000000000000000
[    0.254307] RDX: 0000000000000002 RSI: 0000000000000000 RDI: ffff880013783e08
[    0.254307] RBP: ffff880013789dd0 R08: 0000000000000282 R09: 0000000000000000
[    0.254308] R10: 0000000000000000 R11: 0000000000000005 R12: ffffffff81c7fc60
[    0.254308] R13: 0000000000000000 R14: ffffffff81c5f400 R15: ffff880013b149c0
[    0.254309] FS:  0000000000000000(0000) GS:ffff880013b00000(0000) knlGS:0000000000000000
[    0.254309] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[    0.254310] CR2: 0000000000000000 CR3: 0000000001bfd000 CR4: 00000000000006e0
[    0.254316] Stack:
[    0.254317]  ffff880013789e20 ffffffff8109c60d 0000000000000282 ffff880013789e78
[    0.254318]  ffff880013789e20 ffffffff81c5f300 ffffffff81c7fc60 ffff880013b0eb20
[    0.254319]  ffffffff81c5f400 ffffffff81c5f300 ffff880013789ec8 ffffffff810ceb3c
[    0.254319] Call Trace:
[    0.254338]  [<ffffffff8109c60d>] set_cpus_allowed_ptr+0x3d/0x110
[    0.254344]  [<ffffffff810ceb3c>] rcu_gp_kthread+0xec/0x8d0
[    0.254349]  [<ffffffff810b0410>] ? abort_exclusive_wait+0xb0/0xb0
[    0.254350]  [<ffffffff810cea50>] ? rcu_process_callbacks+0x5d0/0x5d0
[    0.254356]  [<ffffffff8108b852>] kthread+0xd2/0xf0
[    0.254358]  [<ffffffff8108b780>] ? kthread_create_on_node+0x180/0x180
[    0.254372]  [<ffffffff81831e7c>] ret_from_fork+0x7c/0xb0
[    0.254374]  [<ffffffff8108b780>] ? kthread_create_on_node+0x180/0x180
[    0.254383] Code: 1f 00 4c 8b 44 07 08 48 83 c0 08 4c 3b 04 06 75 49 83 c1 01 44 39 c9 75 e9 f6 c2 3f b8 01 00 00 00 74 30 89 d0 48 63 c9 c1 f8 1f <48> 8b 34 ce 48 33 34 cf c1 e8 1a 8d 0c 02 83 e1 3f 29 c1 b8 01 [    0.254385] RIP  [<ffffffff813d93c1>] __bitmap_equal+0x51/0x90
[    0.254385]  RSP <ffff880013789dd0>
[    0.254386] CR2: 0000000000000000
[    0.254397] ---[ end trace 685126bdf0ef28ff ]---
[    0.254398] Kernel panic - not syncing: Fatal exception

Attached dmesg for the parent commit, too, to help confirm whether it is a noise error.


git bisect start a558e309f99cf8b809691417324c6770e10bb614 c9eaa447e77efe77b7fa4c953bd62de8297fd6c5 --
git bisect good 812cae8dd849450dcdf4bcf2b180c46a6b9dc165  # 09:08     20+      1  rcu: Handle obsolete references to TINY_PREEMPT_RCU
git bisect good 2486acf2d73ff255fadc92a4ee45b6c466ac15ec  # 09:15     20+      0  torture: Avoid format string leak to thead name
git bisect good aaf0bec87d07b6ccede533c6eaac3dcd7eed7638  # 09:28     20+      0  MAINTAINERS: Add "R:" designated-reviewers tag
git bisect good 8f23f609aea25eef7a70a81749c1cc01f908b34c  # 09:39     20+      0  rcu: Add designated reviewers for RCU
git bisect good b5ec6ac52922763165166f6aa6ffde948d4dd067  # 09:51     20+      1  Update RCU maintainership
# first bad commit: [a558e309f99cf8b809691417324c6770e10bb614] rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs
git bisect good b5ec6ac52922763165166f6aa6ffde948d4dd067  # 09:56     60+      2  Update RCU maintainership
git bisect  bad a558e309f99cf8b809691417324c6770e10bb614  # 09:56      0-     30  rcu: Bind grace-period kthreads to non-NO_HZ_FULL CPUs
git bisect good 54539cd217d687d9acf385eab22ec02b3f7a86a0  # 10:10     60+      1  Merge branch 'for-3.15-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
git bisect good d0b2e95e0bccbe33652d76f4979603447de2e048  # 10:24     60+      0  Add linux-next specific files for 20140604


This script may reproduce the error.

-----------------------------------------------------------------------------
#!/bin/bash

kernel=$1
initrd=yocto-minimal-x86_64.cgz

wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/blob/master/initrd/$initrd

kvm=(
	qemu-system-x86_64 -cpu kvm64 -enable-kvm 	
	-kernel $kernel
	-initrd $initrd
	-smp 2
	-m 256M
	-net nic,vlan=0,macaddr=00:00:00:00:00:00,model=virtio
	-net user,vlan=0
	-net nic,vlan=1,model=e1000
	-net user,vlan=1
	-boot order=nc
	-no-reboot
	-watchdog i6300esb
	-serial stdio
	-display none
	-monitor null
)

append=(
	debug
	sched_debug
	apic=debug
	ignore_loglevel
	sysrq_always_enabled
	panic=10
	prompt_ramdisk=0
	earlyprintk=ttyS0,115200
	console=ttyS0,115200
	console=tty0
	vga=normal
	root=/dev/ram0
	rw
)

"${kvm[@]}" --append "${append[*]}"
-----------------------------------------------------------------------------

Thanks,
Jet


View attachment "dmesg-yocto-ivb44-33:20140605090019:x86_64-rhel:3.15.0-rc1-00084-ga558e30:1" of type "text/plain" (34759 bytes)

View attachment "Attached Message Part" of type "text/plain" (86 bytes)

View attachment "config-3.15.0-rc1-00084-ga558e30" of type "text/plain" (123299 bytes)

View attachment "dmesg-quantal-ivb44-108:20140605095447:x86_64-rhel:3.15.0-rc1-00083-gb5ec6ac:1" of type "text/plain" (49319 bytes)

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