FYI, we noticed the following commit (built with gcc-4.9): commit: 30f33126feca0fe16df9e9302ffc28a953e2eb37 ("drm/ttm: Fix bo_global and mem_global kfree error") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master in testcase: boot on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 1G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +-----------------------------------------------------------------------------+------------+------------+ | | 0bf19b9fda | 30f33126fe | +-----------------------------------------------------------------------------+------------+------------+ | boot_successes | 0 | 0 | | boot_failures | 246 | 246 | | Mem-Info | 246 | 246 | | BUG:unable_to_handle_kernel | 64 | 4 | | Oops:#[##] | 64 | 4 | | EIP:kfree | 64 | | | Kernel_panic-not_syncing:Fatal_exception | 64 | 4 | | BUG:soft_lockup-CPU##stuck_for#s | 181 | 231 | | EIP:rcu_read_lock_held | 3 | 3 | | calltrace:threadfunc | 4 | 10 | | Kernel_panic-not_syncing:softlockup:hung_tasks | 181 | 231 | | EIP:lock_is_held_type | 61 | 62 | | EIP:lockdep_rht_bucket_is_held | 2 | 2 | | EIP:lock_acquire | 32 | 40 | | EIP:lock_release | 27 | 33 | | EIP:thread_lookup_test | 25 | 37 | | EIP:memcmp | 7 | 5 | | EIP:lockdep_rht_mutex_is_held | 3 | 1 | | EIP:___might_sleep | 1 | 2 | | EIP:lock_acquired | 1 | 3 | | EIP:_cond_resched | 2 | 1 | | EIP:ftrace_likely_update | 2 | 6 | | EIP:rhashtable_rehash_table | 3 | 1 | | EIP:__local_bh_enable_ip | 1 | 6 | | EIP:threadfunc | 3 | 9 | | EIP:drm_mm_insert_node_in_range | 4 | | | EIP:rhashtable_lookup_one | 1 | 8 | | EIP:debug_lockdep_rcu_enabled | 2 | 6 | | INFO:task_blocked_for_more_than#seconds | 1 | | | Kernel_panic-not_syncing:hung_task:blocked_tasks | 1 | | | EIP:__local_bh_disable_ip | 1 | 2 | | kobject(#):tried_to_init_an_initialized_object,something_is_seriously_wrong | 0 | 15 | | EIP:ttm_mem_global_init | 0 | 4 | | EIP:jhash | 0 | 4 | +-----------------------------------------------------------------------------+------------+------------+ [ 84.700873] [TTM] Finalizing DMA pool allocator [ 84.701807] [TTM] Zone kernel: Used memory at exit: 0 kiB [ 84.702608] [TTM] Zone highmem: Used memory at exit: 0 kiB [ 84.703666] [drm] Found bochs VGA, ID 0xb0c0. [ 84.704269] [drm] Framebuffer size 16384 kB @ 0xfd000000, mmio @ 0xfebf0000. [ 84.705345] kobject (11120a87): tried to init an initialized object, something is seriously wrong. [ 84.706614] CPU: 0 PID: 1 Comm: swapper Tainted: G T 4.20.0-rc1-00144-g30f3312 #1 [ 84.707774] Call Trace: [ 84.708118] dump_stack+0x16/0x26 [ 84.708561] kobject_init+0x6a/0x80 [ 84.709032] kobject_init_and_add+0x12/0x50 [ 84.709614] ttm_mem_global_init+0x86/0x440 [ 84.710957] ? __mutex_lock+0x716/0x7d0 [ 84.711519] ? vprintk_emit+0xfd/0x270 [ 84.712019] ? vprintk_default+0x17/0x20 [ 84.712552] ttm_bo_device_init+0x19a/0x310 [ 84.713104] ? printk+0x13/0x15 [ 84.713535] bochs_mm_init+0x37/0xb0 [ 84.716829] bochs_pci_probe+0x107/0x180 [ 84.717260] pci_device_probe+0x7e/0xf0 [ 84.717695] really_probe+0xb4/0x340 [ 84.718139] driver_probe_device+0x111/0x130 [ 84.718615] __driver_attach+0xb9/0xc0 [ 84.719033] ? driver_probe_device+0x130/0x130 [ 84.719526] bus_for_each_dev+0x4b/0x90 [ 84.720115] driver_attach+0x19/0x20 [ 84.720500] ? driver_probe_device+0x130/0x130 [ 84.720962] bus_add_driver+0x187/0x200 [ 84.721365] ? qxl_init+0x66/0x66 [ 84.721736] ? qxl_init+0x66/0x66 [ 84.722154] driver_register+0x56/0xf0 [ 84.722569] __pci_register_driver+0x50/0x60 [ 84.723152] bochs_init+0x43/0x5c [ 84.723533] do_one_initcall+0x104/0x3c2 [ 84.723959] ? parse_args+0xa0/0x280 [ 84.724351] kernel_init_freeable+0x2b4/0x460 [ 84.724828] ? rest_init+0x110/0x110 [ 84.725221] kernel_init+0xd/0xf0 [ 84.725589] ret_from_fork+0x19/0x24 [ 84.726105] BUG: unable to handle kernel paging request at 7eac1104 [ 84.729246] *pdpt = 0000000000000000 *pde = 0000000000000000 [ 84.730024] Oops: 0002 [#1] [ 84.730024] CPU: 0 PID: 1 Comm: swapper Tainted: G T 4.20.0-rc1-00144-g30f3312 #1 [ 84.730024] EIP: ttm_mem_global_init+0x388/0x440 [ 84.730024] Code: 89 c3 0f b6 d0 b8 e0 20 a5 c2 e8 03 7f bd ff 84 db 58 0f 85 aa 00 00 00 8b 86 8c 00 00 00 8b 5d b0 8d 50 01 89 96 8c 00 00 00 <89> 9c 86 84 00 00 00 e9 5c fe ff ff 8d 74 26 00 89 f0 e8 51 02 ab [ 84.730024] EAX: eeca1400 EBX: eeca2e00 ECX: 00000000 EDX: eeca1401 [ 84.730024] ESI: c383c080 EDI: 00000000 EBP: f2535df0 ESP: f2535d90 [ 84.730024] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00210246 [ 84.730024] CR0: 80050033 CR2: 7eac1104 CR3: 02be9000 CR4: 000406b0 [ 84.730024] Call Trace: [ 84.730024] ? vprintk_emit+0xfd/0x270 [ 84.730024] ? vprintk_default+0x17/0x20 [ 84.730024] ttm_bo_device_init+0x19a/0x310 [ 84.730024] ? printk+0x13/0x15 [ 84.730024] bochs_mm_init+0x37/0xb0 [ 84.730024] bochs_pci_probe+0x107/0x180 [ 84.730024] pci_device_probe+0x7e/0xf0 [ 84.730024] really_probe+0xb4/0x340 [ 84.730024] driver_probe_device+0x111/0x130 [ 84.730024] __driver_attach+0xb9/0xc0 [ 84.730024] ? driver_probe_device+0x130/0x130 [ 84.730024] bus_for_each_dev+0x4b/0x90 [ 84.730024] driver_attach+0x19/0x20 [ 84.730024] ? driver_probe_device+0x130/0x130 [ 84.730024] bus_add_driver+0x187/0x200 [ 84.730024] ? qxl_init+0x66/0x66 [ 84.730024] ? qxl_init+0x66/0x66 [ 84.730024] driver_register+0x56/0xf0 [ 84.730024] __pci_register_driver+0x50/0x60 [ 84.730024] bochs_init+0x43/0x5c [ 84.730024] do_one_initcall+0x104/0x3c2 [ 84.730024] ? parse_args+0xa0/0x280 [ 84.730024] kernel_init_freeable+0x2b4/0x460 [ 84.730024] ? rest_init+0x110/0x110 [ 84.730024] kernel_init+0xd/0xf0 [ 84.730024] ret_from_fork+0x19/0x24 [ 84.730024] CR2: 000000007eac1104 [ 84.730024] ---[ end trace d1d09e50282c959c ]--- [ 84.730024] EIP: ttm_mem_global_init+0x388/0x440 [ 84.730024] Code: 89 c3 0f b6 d0 b8 e0 20 a5 c2 e8 03 7f bd ff 84 db 58 0f 85 aa 00 00 00 8b 86 8c 00 00 00 8b 5d b0 8d 50 01 89 96 8c 00 00 00 <89> 9c 86 84 00 00 00 e9 5c fe ff ff 8d 74 26 00 89 f0 e8 51 02 ab [ 84.730024] EAX: eeca1400 EBX: eeca2e00 ECX: 00000000 EDX: eeca1401 [ 84.730024] ESI: c383c080 EDI: 00000000 EBP: f2535df0 ESP: c2bed4bc [ 84.730024] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00210246 [ 84.730024] CR0: 80050033 CR2: 7eac1104 CR3: 02be9000 CR4: 000406b0 [ 84.730024] Kernel panic - not syncing: Fatal exception [ 84.730024] Kernel Offset: disabled Elapsed time: 90 qemu-img create -f qcow2 disk-vm-snb-openwrt-ia32-22-0 256G To reproduce: git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp qemu -k job-script # job-script is attached in this email Thanks, Rong Chen