FYI, we noticed the below changes on git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master commit 945fa9c631b04febe295a3a2a00c7e4a3cfb97db ("torture: Dump ftrace buffer when the RCU grace period stalls") We think the commit may reveal a existing bug. +------------------------------------------+------------+------------+ > | 499c632dce | 945fa9c631 | +------------------------------------------+------------+------------+ > boot_successes | 11 | 0 | > boot_failures | 14 | 11 | > BUG:kernel_test_oversize | 14 | | > BUG:unable_to_handle_kernel | 0 | 11 | > Oops | 0 | 11 | > RIP:print_trace_line | 0 | 11 | > Kernel_panic-not_syncing:Fatal_exception | 0 | 11 | > backtrace:rcu_torture_stats | 0 | 11 | +------------------------------------------+------------+------------+ [ 148.360961] Testing event xfs_buf_delwri_split: [ 148.619386] Dumping ftrace buffer: [ 148.619956] --------------------------------- [ 148.620088] BUG: unable to handle kernel NULL pointer dereference at (null) [ 148.620088] IP: [] print_trace_line+0x26d/0xb90 [ 148.620088] PGD 0 [ 148.620088] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 148.620088] CPU: 0 PID: 83 Comm: rcu_torture_sta Not tainted 3.15.0-rc1-00026-g945fa9c #1 [ 148.620088] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014 [ 148.625508] OK [ 148.620088] Testing event xfs_buf_delwri_queued: [ 148.620088] task: ffff880000050000 ti: ffff8800a90ea000 task.ti: ffff8800a90ea000 [ 148.620088] RIP: 0010:[] [] print_trace_line+0x26d/0xb90 [ 148.620088] RSP: 0000:ffff8800a90ebca8 EFLAGS: 00010002 [ 148.620088] RAX: 0000000000000000 RBX: ffffffff83f58340 RCX: 0000000000000000 [ 148.620088] RDX: 0000000000000002 RSI: 0000000000000002 RDI: ffffffff83f59439 [ 148.620088] RBP: ffff8800a90ebcd8 R08: 0000000000000000 R09: 0000000000013b35 [ 148.620088] R10: 0000000000013b35 R11: 00000000000460b0 R12: 0000000003bd1201 [ 148.620088] R13: ffffffff83f5941c R14: ffff880139367014 R15: fffffffffffffffc [ 148.620088] FS: 0000000000000000(0000) GS:ffff88013f400000(0000) knlGS:0000000000000000 [ 148.620088] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 148.620088] CR2: 0000000000000000 CR3: 00000000029ac000 CR4: 00000000000006f0 [ 148.620088] Stack: [ 148.620088] 0000000000000000 0000000000000202 0000000000000001 0000000000000000 [ 148.620088] ffffffff83f59420 fffffffffffffffc ffff8800a90ebd10 ffffffff8128601e [ 148.620088] ffff8800a810014f ffffffff83f07c6c ffff8800a90ebdb8 ffff8800a90ebe10 [ 148.620088] Call Trace: [ 148.620088] [] ftrace_dump+0x2de/0x5a0 [ 148.620088] [] rcutorture_trace_dump+0x86/0x90 [ 148.620088] [] rcu_torture_printk+0x6b2/0x710 [ 148.620088] [] ? rcu_torture_stats_print+0xe0/0xe0 [ 148.620088] [] rcu_torture_stats_print+0x71/0xe0 [ 148.620088] [] rcu_torture_stats+0x57/0xd0 [ 148.620088] [] kthread+0x191/0x1a0 [ 148.620088] [] ? insert_kthread_work+0x170/0x170 [ 148.620088] [] ret_from_fork+0x7c/0xb0 [ 148.620088] [] ? insert_kthread_work+0x170/0x170 [ 148.620088] Code: 01 48 83 c2 02 48 83 04 d5 40 c1 fe 82 01 84 c0 0f 85 d0 00 00 00 48 83 05 70 38 cd 02 01 48 8b 8b d0 10 00 00 8b b3 00 21 00 00 <48> 0f a3 31 19 c0 48 83 05 5d 38 cd 02 01 85 c0 40 0f 95 c7 48 [ 148.620088] RIP [] print_trace_line+0x26d/0xb90 [ 148.620088] RSP [ 148.620088] CR2: 0000000000000000 [ 148.620088] ---[ end trace 4f8998a92417facf ]--- [ 148.620088] Kernel panic - not syncing: Fatal exception Thanks, Ying Huang