Greetings, We got the follow kernel panic dmesg(full dmesg is attached): [ 7.781306] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 7.791041] IP: [] acpi_find_child_device+0x23/0xc3 [ 7.798776] PGD 0 [ 7.801547] Oops: 0000 [#1] SMP [ 7.805759] Modules linked in: [ 7.809698] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc1-01248-g32f2968 #1874 [ 7.819272] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS RMLSDP.86I.R3.27.D685.1305151734 05/15/2013 [ 7.831275] task: ffff88080cd98000 ti: ffff88080cda0000 task.ti: ffff88080cda0000 [ 7.840461] RIP: 0010:[] [] acpi_find_child_device+0x23/0xc3 [ 7.851282] RSP: 0000:ffff88080cda19b0 EFLAGS: 00010282 [ 7.857666] RAX: ffff88080ba52098 RBX: ffff88080cda1a18 RCX: 0000000000000000 [ 7.866089] RDX: 0000000000000001 RSI: 0000000000080000 RDI: 0000000000000000 [ 7.874512] RBP: ffff88080cda19e8 R08: 0000000000000000 R09: 0000000000000000 [ 7.882935] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000 [ 7.891361] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000080000 [ 7.899785] FS: 0000000000000000(0000) GS:ffff880818a00000(0000) knlGS:0000000000000000 [ 7.909652] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 7.916521] CR2: 0000000000000018 CR3: 000000000220c000 CR4: 00000000001407e0 [ 7.924945] Stack: [ 7.927632] ffffffff81550091 ffff88080ba53098 ffff88080cda1a18 ffff88080ba53098 [ 7.937044] ffffffff822b6a70 ffff88080ba52098 ffff88080ba43000 ffff88080cda1a00 [ 7.946443] ffffffff81548f73 ffff88080ba53098 ffff88080cda1a30 ffffffff8154fac6 [ 7.955843] Call Trace: [ 7.959021] [] ? acpi_bus_get_device+0x21/0x3e [ 7.966281] [] acpi_pci_find_device+0x3c/0x54 [ 7.973442] [] acpi_platform_notify+0x3a/0x6c [ 7.980603] [] device_add+0x143/0x550 [ 7.986988] [] pci_device_add+0x123/0x13f [ 7.993760] [] pci_scan_single_device+0x93/0x9e [ 8.001118] [] pci_scan_slot+0x57/0x108 [ 8.007696] [] pci_scan_child_bus+0x53/0x10d [ 8.023921] [] pci_scan_bridge+0x1d2/0x4ec [ 8.030792] [] pci_scan_child_bus+0xc5/0x10d [ 8.037848] [] pci_scan_bridge+0x1d2/0x4ec [ 8.044718] [] ? pci_scan_single_device+0x41/0x9e [ 8.052268] [] pci_scan_child_bus+0xc5/0x10d [ 8.059327] [] pci_acpi_scan_root+0x31f/0x3aa [ 8.066488] [] acpi_pci_root_add+0x35e/0x45a [ 8.073554] [] acpi_bus_attach+0x86/0xf6 [ 8.080220] [] acpi_bus_attach+0xe2/0xf6 [ 8.086896] [] acpi_bus_attach+0xe2/0xf6 [ 8.093573] [] acpi_bus_scan+0x5b/0x6b [ 8.100059] [] ? acpi_sleep_proc_init+0x2a/0x2a [ 8.107414] [] acpi_scan_init+0x61/0x18f [ 8.114090] [] ? acpi_sleep_proc_init+0x2a/0x2a [ 8.121435] [] acpi_init+0x24f/0x267 [ 8.127724] [] do_one_initcall+0xa4/0x13a [ 8.134497] [] ? parse_args+0x261/0x33f [ 8.141081] [] kernel_init_freeable+0x1d9/0x25f [ 8.148438] [] ? do_early_param+0x88/0x88 [ 8.155209] [] ? rest_init+0xcd/0xcd [ 8.161496] [] kernel_init+0xe/0x109 [ 8.167782] [] ret_from_fork+0x7c/0xb0 [ 8.174263] [] ? rest_init+0xcd/0xcd [ 8.180550] Code: ff ff 5a 5b 41 5c 5d c3 0f 1f 44 00 00 55 48 89 e5 41 57 49 89 f7 41 56 45 31 f6 41 55 44 0f b6 ea 41 54 45 31 e4 53 48 83 ec 10 <48> 8b 47 18 48 8d 58 d8 48 8d 47 18 48 89 45 c8 48 8d 43 28 48 [ 8.208097] RIP [] acpi_find_child_device+0x23/0xc3 [ 8.215920] RSP [ 8.220261] CR2: 0000000000000018 [ 8.224413] ---[ end trace 56dc910562aec71f ]--- [ 8.230019] Kernel panic - not syncing: Fatal exception And the first bad commit we bisected is: caa223f31b414427e7d12c130587bf3261b257de is the first bad commit commit caa223f31b414427e7d12c130587bf3261b257de Author: Rafael J. Wysocki Date: Mon Nov 25 22:49:35 2013 +0100 PCI / ACPI: Use acpi_find_child_device() for child devices lookup It is much more efficient to use acpi_find_child_device() for child devices lookup in acpi_pci_find_device() and pass ACPI_COMPANION(dev->parent) to it directly instead of obtaining ACPI_HANDLE() of ACPI_COMPANION(dev->parent) and passing it to acpi_find_child() which has to run acpi_bus_get_device() to obtain ACPI_COMPANION(dev->parent) from that again. Signed-off-by: Rafael J. Wysocki Reviewed-by: Aaron Lu :040000 040000 eb2cd7279dafcce191ecc17b442130649366e376 bd1101a919edda8ece2e12b9b152426251cd78f0 M drivers bisect run success # bad: [32f296837b2323b3c8d88e9e97135b2ed1de123f] Merge 'openvswitch/master' into devel-hourly-2013112708 # good: [6ce4eac1f600b34f2f7f58f9cd8f0503d79e42ae] Linux 3.13-rc1 git bisect start '32f296837b2323b3c8d88e9e97135b2ed1de123f' '6ce4eac1f600b34f2f7f58f9cd8f0503d79e42ae' '--' # good: [7b797b94fc2592fa130c44d502fb08adfc015647] Merge 'staging/work-next' into devel-hourly-2013112708 git bisect good 7b797b94fc2592fa130c44d502fb08adfc015647 # bad: [caec74c0c122b289f685372f183be0d75877dea9] Merge 'perf/perf/core' into devel-hourly-2013112708 git bisect bad caec74c0c122b289f685372f183be0d75877dea9 # bad: [93bf277e43d6a22edb7a470634cb5fbb372307da] Merge 'shawnguo/for-next' into devel-hourly-2013112708 git bisect bad 93bf277e43d6a22edb7a470634cb5fbb372307da # bad: [3f127a6bc56a4034016fc53c3add06c5cbc3bc5c] Merge 'm68k/for-3.14' into devel-hourly-2013112708 git bisect bad 3f127a6bc56a4034016fc53c3add06c5cbc3bc5c # bad: [5e445066299a6a0c0a4a73946561e24da3ed6209] Merge 'pm/bleeding-edge' into devel-hourly-2013112708 git bisect bad 5e445066299a6a0c0a4a73946561e24da3ed6209 # bad: [955423d41f199c649b89fe36fc3b3fd8a102a894] ACPI / bind: Redefine acpi_preset_companion() git bisect bad 955423d41f199c649b89fe36fc3b3fd8a102a894 # good: [202317a573b20d77a9abb7c16a3fd5b40cef3d9d] ACPI / scan: Add acpi_device objects for all device nodes in the namespace git bisect good 202317a573b20d77a9abb7c16a3fd5b40cef3d9d # good: [f4b734c35e98c343cd99824153de09e48867b97e] ACPI / hotplug: Drop unfinished global notification handling routines git bisect good f4b734c35e98c343cd99824153de09e48867b97e # good: [c1b5a568803400f131a93cdfdf65e779222122e6] ACPI / bind: Simplify child device lookups git bisect good c1b5a568803400f131a93cdfdf65e779222122e6 # bad: [313d082956729d896f1a12e6892cf2901a7c2987] ACPI / bind: Redefine acpi_get_child() git bisect bad 313d082956729d896f1a12e6892cf2901a7c2987 # bad: [caa223f31b414427e7d12c130587bf3261b257de] PCI / ACPI: Use acpi_find_child_device() for child devices lookup git bisect bad caa223f31b414427e7d12c130587bf3261b257de # first bad commit: [caa223f31b414427e7d12c130587bf3261b257de] PCI / ACPI: Use acpi_find_child_device() for child devices lookup