Issue

• A server using the IBM lin_tape driver experienced a crash due to triggering the hung task (i.e. khungtaskd) panic condition.

INFO: task dsmserv:3563 blocked for more than 500 seconds.
      Not tainted 2.6.32-504.16.2.el6.x86_64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
dsmserv       D 0000000000000000     0  3563   5207 0x00000080
 ffff8809503c77e8 0000000000000082 0000000000011220 ffff8809503c7788
 ffff8809503c77a0 ffff881074fddc70 ffff8809503c7758 ffffffff81126b95
 ffff8809503c77e8 ffffffff81126d33 ffff880ce081f068 ffff8809503c7fd8
Call Trace:
 [<ffffffff81126b95>] ? mempool_alloc_slab+0x15/0x20
 [<ffffffff81126d33>] ? mempool_alloc+0x63/0x140
 [<ffffffff81380069>] ? scsi_get_command+0x89/0xc0
 [<ffffffff8152ad25>] schedule_timeout+0x215/0x2e0
 [<ffffffff8128e1e7>] ? kobject_put+0x27/0x60
 [<ffffffff8152a9a3>] wait_for_common+0x123/0x180
 [<ffffffff81064bc0>] ? default_wake_function+0x0/0x20
 [<ffffffff8152aabd>] wait_for_completion+0x1d/0x20
 [<ffffffff8127791c>] blk_execute_rq+0x8c/0xf0
 [<ffffffff812714d0>] ? freed_request+0x50/0x80
 [<ffffffff812720e6>] ? blk_get_request+0x46/0xa0
 [<ffffffffa0514d98>] lin_tape_blk_rq+0x138/0x590 [lin_tape]
 [<ffffffffa051523a>] tape_execute_scsi_command+0x4a/0xc0 [lin_tape]
 [<ffffffffa0514192>] ? tape_log_cdb+0x32/0x110 [lin_tape]
 [<ffffffffa051a65f>] tape_send_scsi_io+0x1ff/0x4a0 [lin_tape]
 [<ffffffff810b2a3d>] ? get_futex_key+0x18d/0x2d0
 [<ffffffffa051a97b>] tape_send_scsi_cmd+0x7b/0x2d0 [lin_tape]
 [<ffffffff810b231a>] ? futex_wait_queue_me+0xba/0xf0
 [<ffffffffa051fd8f>] tape_set_pos+0x23f/0x520 [lin_tape]
 [<ffffffffa0503ae6>] stiocsetpos+0x16/0x20 [lin_tape]
 [<ffffffffa0501214>] drvioc_exe+0xd4/0x150 [lin_tape]
 [<ffffffffa050e5fd>] lin_tape_drive_ioctl+0x50d/0x1990 [lin_tape]
 [<ffffffffa0503ad0>] ? stiocsetpos+0x0/0x20 [lin_tape]
 [<ffffffffa04f8339>] lin_tape_ioctl_drive+0x169/0x260 [lin_tape]
 [<ffffffffa04f84cd>] lin_tape_ioctl+0x9d/0x100 [lin_tape]
 [<ffffffff811a3a9c>] vfs_ioctl+0x7c/0xa0
 [<ffffffff811a3be4>] do_vfs_ioctl+0x84/0x580
 [<ffffffff81194123>] ? sys_newfstat+0x33/0x40
 [<ffffffff811a4161>] sys_ioctl+0x81/0xa0
 [<ffffffff810e5b6e>] ? __audit_syscall_exit+0x25e/0x290
 [<ffffffff8100b072>] system_call_fastpath+0x16/0x1b
Kernel panic - not syncing: hung_task: blocked tasks
Pid: 179, comm: khungtaskd Not tainted 2.6.32-504.16.2.el6.x86_64 #1
Call Trace:
 [<ffffffff8152971c>] ? panic+0xa7/0x16f
 [<ffffffff810ea046>] ? watchdog+0x246/0x250
 [<ffffffff810e9e00>] ? watchdog+0x0/0x250
 [<ffffffff8109e71e>] ? kthread+0x9e/0xc0
 [<ffffffff8100c20a>] ? child_rip+0xa/0x20
 [<ffffffff8109e680>] ? kthread+0x0/0xc0
 [<ffffffff8100c200>] ? child_rip+0x0/0x20