Greetings, We find commit 38207484cc9 ("intel_idle: use the common cpuidle_[un]register() routines") triggered oops in one of our servers: [ 12.788616] intel_idle: MWAIT substates: 0x2120 [ 12.794106] intel_idle: v0.4 model 0x3F [ 12.798820] intel_idle: lapic_timer_reliable_states 0xffffffff [ 12.807169] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 [ 12.816854] IP: [] kobject_get+0x12/0x44 [ 12.823487] PGD 0 [ 12.826228] Oops: 0002 [#1] SMP [ 12.830406] Modules linked in: [ 12.834310] CPU: 18 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc7-03669-ga961e1e #1 [ 12.843645] Hardware name: Intel Corporation S2600WT/S2600WT, BIOS GRNDSDP1.86B.0018.R02.1310250658 10/25/2013 [ 12.855602] task: ffff880469ff8000 ti: ffff880469810000 task.ti: ffff880469810000 [ 12.864737] RIP: 0010:[] [] kobject_get+0x12/0x44 [ 12.874442] RSP: 0000:ffff880469811d08 EFLAGS: 00010202 [ 12.880803] RAX: 0000000000000001 RBX: 0000000000000010 RCX: 0000000000000000 [ 12.889209] RDX: ffffffff81f8e2ad RSI: 000000000000002f RDI: 0000000000000010 [ 12.897613] RBP: ffff880469811d10 R08: 0000000000000007 R09: ffffffff81f8e2ad [ 12.906016] R10: ffff88084d2e8630 R11: 0000000000000001 R12: 0000000000000000 [ 12.914419] R13: 0000000000000010 R14: 000000000000fc20 R15: 0000000000000000 [ 12.922824] FS: 0000000000000000(0000) GS:ffff88086ec80000(0000) knlGS:0000000000000000 [ 12.932645] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 12.939495] CR2: 0000000000000048 CR3: 000000000220c000 CR4: 00000000001407e0 [ 12.947900] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 12.956302] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 12.964704] Stack: [ 12.967367] ffff88084d2e86a8 ffff880469811d58 ffffffff814f084d ffff88084d2e86a8 [ 12.976724] 0000000000000000 ffff88084d2e86a8 0000000000000000 0000000000000010 [ 12.986080] 000000000000fc20 0000000000000000 ffff880469811dc8 ffffffff814f0a90 [ 12.995443] Call Trace: [ 12.998594] [] kobject_add_internal+0x5a/0x22a [ 13.005832] [] kobject_init_and_add+0x73/0x7e [ 13.012975] [] ? kmem_cache_alloc_trace+0x4c/0x1b8 [ 13.020602] [] ? cpuidle_add_sysfs+0x32/0xb1 [ 13.027645] [] ? sysfs_new_dirent+0x51/0x102 [ 13.034686] [] cpuidle_add_sysfs+0x83/0xb1 [ 13.041534] [] cpuidle_register_device+0xab/0xfb [ 13.048964] [] cpuidle_register+0x79/0xae [ 13.055719] [] intel_idle_init+0x2c8/0x313 Full dmesg and kconfig are attached. Thanks, Fengguang