Hi Kyle,

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

git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git for-next

commit 316638a5030a04bb3259dcbca0632281001a4b24 Author: Kyle Chamberlin kylechamberlin@project20million.org AuthorDate: Fri Nov 28 13:59:56 2014 -0500 Commit: Takashi Iwai tiwai@suse.de CommitDate: Sat Nov 29 21:34:47 2014 +0100

ALSA: virmidi: fixed code style issues

Fixed some minor code style issues and also removed some assignments inside of if conditionals.

Signed-off-by: Kyle Chamberlin kylechamberlin@project20million.org Signed-off-by: Takashi Iwai tiwai@suse.de

In particular, this chunk introduced the behavior change:

- if ((err = snd_card_register(card)) == 0) { + err = snd_card_register(card); + if (err) {

+-------------------------------------------------+------------+------------+------------+ | | 31514bfb4a | 316638a503 | 795172aaa6 | +-------------------------------------------------+------------+------------+------------+ | boot_successes | 67 | 0 | 0 | | boot_failures | 13 | 20 | 14 | | BUG:kernel_early_hang_without_any_printk_output | 13 | 0 | 2 | | BUG:unable_to_handle_kernel | 0 | 20 | 12 | | Oops | 0 | 20 | 12 | | EIP_is_at_snd_card_free | 0 | 20 | 12 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 20 | 12 | | backtrace:platform_device_unregister | 0 | 20 | 12 | | backtrace:alsa_card_virmidi_init | 0 | 20 | 12 | | backtrace:kernel_init_freeable | 0 | 20 | 12 | +-------------------------------------------------+------------+------------+------------+

[ 1.688337] usbcore: registered new interface driver line6usb [ 1.689386] dgap: dgap-1.3-16, Digi International Part Number 40002347_C [ 1.690258] dgap: For the tools package please visit http://www.digi.com [ 1.694793] BUG: unable to handle kernel NULL pointer dereference at 000002a0 [ 1.695739] IP: [<7940555f>] snd_card_free+0x36/0x7f [ 1.696409] *pde = 00000000 [ 1.696686] Oops: 0002 [#1] [ 1.696686] Modules linked in: [ 1.696686] CPU: 0 PID: 1 Comm: swapper Not tainted 3.18.0-rc5-00179-g316638a #101 [ 1.696686] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014 [ 1.696686] task: 8a068000 ti: 8a064000 task.ti: 8a064000 [ 1.696686] EIP: 0060:[<7940555f>] EFLAGS: 00010246 CPU: 0 [ 1.696686] EIP is at snd_card_free+0x36/0x7f [ 1.696686] EAX: 00000000 EBX: 8a065e04 ECX: 7a354880 EDX: 798a5d21 [ 1.696686] ESI: 00000000 EDI: 00000000 EBP: 8a065e44 ESP: 8a065e04 [ 1.696686] DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068 [ 1.696686] CR0: 8005003b CR2: 000002a0 CR3: 01d49000 CR4: 000006d0 [ 1.696686] Stack: [ 1.696686] 00000000 00000001 dead4ead ffffffff ffffffff 7a354880 00000000 00000000 [ 1.696686] 798a5d21 00000000 00000000 8a065e30 8a065e30 006d61bc 7808440c 00000001 [ 1.696686] 8a065e4c 7943d967 8a065e54 792c0e93 8a065e68 792befa9 78084440 7808440c [ 1.696686] Call Trace: [ 1.696686] [<7943d967>] snd_virmidi_remove+0x13/0x17 [ 1.696686] [<792c0e93>] platform_drv_remove+0x14/0x16 [ 1.696686] [<792befa9>] __device_release_driver+0xc1/0x121 [ 1.696686] [<792bf028>] device_release_driver+0x1f/0x2a [ 1.696686] [<792be929>] bus_remove_device+0x166/0x17d [ 1.696686] [<792bb4ad>] device_del+0x14b/0x1d8 [ 1.696686] [<792bb4ad>] ? device_del+0x14b/0x1d8 [ 1.696686] [<792c1407>] platform_device_del+0x32/0xa3 [ 1.696686] [<792c1488>] platform_device_unregister+0x10/0x1a [ 1.696686] [<79cee7bf>] alsa_card_virmidi_init+0xd1/0x118 [ 1.696686] [<79cee6ee>] ? alsa_seq_midi_init+0x34/0x34 [ 1.696686] [<79000551>] do_one_initcall+0x186/0x288 [ 1.696686] [<79cb4400>] ? rdinit_setup+0x18/0x22 [ 1.696686] [<79060c87>] ? parse_args+0x4a6/0x579 [ 1.696686] [<7906be5f>] ? local_clock+0x2b/0x35 [ 1.696686] [<79cb44f6>] ? do_early_param+0xac/0xac [ 1.696686] [<79cb4f46>] kernel_init_freeable+0xfd/0x1bd [ 1.696686] [<79cb4f46>] ? kernel_init_freeable+0xfd/0x1bd [ 1.696686] [<7959bbfc>] kernel_init+0xe/0x13c [ 1.696686] [<795a7cc0>] ret_from_kernel_thread+0x20/0x30 [ 1.696686] [<7959bbee>] ? rest_init+0xa7/0xa7 [ 1.696686] Code: 26 00 89 c6 65 a1 14 00 00 00 89 45 f4 31 c0 c7 45 c0 00 00 00 00 8d 5d c0 b9 80 48 35 7a ba 21 5d 8a 79 8d 45 c4 e8 bc b2 c6 ff <89> 9e a0 02 00 00 89 f0 e8 80 fe ff ff 85 c0 0f 95 c2 0f b6 f2 [ 1.696686] EIP: [<7940555f>] snd_card_free+0x36/0x7f SS:ESP 0068:8a065e04 [ 1.696686] CR2: 00000000000002a0 [ 1.696686] ---[ end trace bc9b8dd3625e806d ]--- [ 1.696686] Kernel panic - not syncing: Fatal exception

git bisect start 795172aaa6701c4b66b449e79b49c41e044156c6 5d01410fe4d92081f349b013a2e7a95429e4f2c9 -- git bisect bad 5d81516a74d44d9301e140ff97e06b37eaf5831d # 06:13 0- 13 Merge 'luto/userns/setgroups' into devel-lkp-hsx01-smoke-201411300558 git bisect good b5675b9e191a3981a38f5c94b6dd8b6fa4ba8091 # 06:23 20+ 3 0day base guard for 'devel-lkp-hsx01-smoke-201411300558' git bisect bad e929ef74cdd822177ad2322514a40127ad1e696c # 06:31 0- 4 Merge 'sound/for-next' into devel-lkp-hsx01-smoke-201411300558 git bisect good 2603fe21b764eb7412598c8c6cd6199fb8b1d9c5 # 06:41 20+ 10 ALSA: es18xx: Add GPO controls git bisect good 2bfb14c3b8fbc787ff4478f9d77ecee78cb922fe # 06:51 20+ 0 ALSA: usb-audio: Add Xonar U1 resume support git bisect good 37e661ee10c6d0d1310c62b3d29ae9a63073ac5d # 06:58 20+ 5 ALSA: hda - Add AZX_DCAPS_SNOOP_OFF (and refactor snoop setup) git bisect good 6eb6c81eee2a6270b39ca02a446f3ccece24b6f8 # 07:16 20+ 0 ALSA: dice: Split stream functionality into a file git bisect good 8832c5a74ba3506c51b6637ac78941fcd21afbef # 07:25 20+ 0 ALSA: speakers: Rename to oxfw and rename some members git bisect good 3713d93a6a12f8629c2660bb4a30d48b98105fca # 07:32 20+ 4 ALSA: oxfw: Split PCM functionality to a new file git bisect bad 316638a5030a04bb3259dcbca0632281001a4b24 # 07:40 0- 17 ALSA: virmidi: fixed code style issues git bisect good 31514bfb4ab8ba6f93b5ce5fcc543cb2ac4f96e5 # 07:46 20+ 1 ALSA: oxfw: Split control functionality to a new file # first bad commit: [316638a5030a04bb3259dcbca0632281001a4b24] ALSA: virmidi: fixed code style issues git bisect good 31514bfb4ab8ba6f93b5ce5fcc543cb2ac4f96e5 # 07:48 60+ 13 ALSA: oxfw: Split control functionality to a new file # extra tests on HEAD of linux-devel/devel-lkp-hsx01-smoke-201411300558 git bisect bad 795172aaa6701c4b66b449e79b49c41e044156c6 # 07:48 0- 14 0day head guard for 'devel-lkp-hsx01-smoke-201411300558' # extra tests on tree/branch sound/for-next git bisect bad 316638a5030a04bb3259dcbca0632281001a4b24 # 07:49 0- 20 ALSA: virmidi: fixed code style issues # extra tests on tree/branch linus/master git bisect good 7a5a4f978750756755dc839014e13d1b088ccc8e # 07:51 60+ 10 Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip # extra tests on tree/branch next/master git bisect good 29340b8ee0b4def844aa8d6b09babcede80993d2 # 07:54 60+ 80 Add linux-next specific files for 20141128

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 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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