业务运行过程中，Linux系统僵死，屏幕无任何有效打印信息，网络中断、键盘鼠标没有任何响应。这种故障现象，可能是因为Linux内核死锁导致。由于无任何有效打印信息，内核日志中也没有记录，就无法定位故障根因。
如何让Linux内核在僵死前打印相关信息，对问题定位尤为关键。其中一个有效手段是打开“Kernel Hacking”选项，然后重新编译内核。
对于Linux内核死锁有帮助的几个配置选项有：
[*] Detect Soft Lockups
[ ] Panic (Reboot) On Soft Lockups
[*] Detect Hung Tasks
(120) Default timeout for hung task detection (in seconds)
[*] Panic (Reboot) On Hung Tasks
[ ] Lock usage statistics
[ ] Spinlock debugging: sleep-inside-spinlock checking
下面一个实例是在SLES11.1 2.6.32.12-0.7内核中系统僵死前，检测到内核死锁并panic，打印出了死锁进程和信息。
ftp D ffff88010d7c5978 4472 22481 4259 0x00000000
ffff880031d1dd08 0000000000000016 ffff8801025cf6f8 0000000000000005
ffff880031d1dc08 ffff880031d1dfd8 000000000000ca98 00000000001d1580
0000000000004000 00000000001d1580 ffff880031d1dca8 ffffffff8108970c
Call Trace:
[] ? __lock_acquire+0xf7f/0x1038
[] ? sched_clock_cpu+0x9a/0x183
[] ? mark_held_locks+0x6e/0xa3
[] ? mutex_lock_nested+0x2cf/0x4ff
[] mutex_lock_nested+0x2e5/0x4ff
[] ? generic_file_aio_write+0x62/0xea
[] ? generic_file_aio_write+0x62/0xea
[] generic_file_aio_write+0x62/0xea
[] do_sync_write+0xee/0x157
[] ? autoremove_wake_function+0x0/0x4d
[] vfs_write+0xed/0x1d1
[] sys_write+0x5c/0x9f
[] system_call_fastpath+0x16/0x1b
1 lock held by ftp/22481:
#0: (&sb->s_type->i_mutex_key#5){+.+.+.}, at: [] generic_file_aio_write+0x62/0xea
Kernel panic – not syncing: hung_task: blocked tasks
Pid: 536, comm: khungtaskd Not tainted 2.6.32.120609_new #14
Call Trace:
[] panic+0x9f/0x228
[] watchdog+0x33c/0x3a2
[] ? watchdog+0x120/0x3a2
[] ? watchdog+0x0/0x3a2
[] kthread+0xa0/0xaf
[] child_rip+0xa/0x20
[] ? finish_task_switch+0x0/0xfe
[] ? restore_args+0x0/0x30
[] ? kthreadd+0xc0/0x17b
[] ? kthread+0x0/0xaf
[] ? child_rip+0x0/0x20