http blocked for more than 120 seconds

Mar 26 08:13:01 localhost kernel: INFO: task flush-8:0:26079 blocked for more than 120 seconds.
Mar 26 08:13:01 localhost kernel: Tainted: P --------------- 2.6.32-431.el6.x86_64 #1
Mar 26 08:13:01 localhost kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 26 08:13:01 localhost kernel: flush-8:0 D 0000000000000001 0 26079 2 0x00000080
Mar 26 08:13:01 localhost kernel: ffff8804359118c0 0000000000000046 0000000000000000 ffff880436a5cb18
Mar 26 08:13:01 localhost kernel: ffff880435911860 ffffffff81068a53 ffffffffa0109300 ffff880436a5cb18
Mar 26 08:13:01 localhost kernel: ffff880436a5d098 ffff880435911fd8 000000000000fbc8 ffff880436a5d098
Mar 26 08:13:01 localhost kernel: Call Trace:
Mar 26 08:13:01 localhost kernel: [<ffffffff81068a53>] ? dequeue_entity+0x113/0x2e0
Mar 26 08:13:01 localhost kernel: [<ffffffffa0109300>] ? noalloc_get_block_write+0x0/0x60 [ext4]
Mar 26 08:13:01 localhost kernel: [<ffffffff8111f930>] ? sync_page+0x0/0x50
Mar 26 08:13:01 localhost kernel: [<ffffffff815280a3>] io_schedule+0x73/0xc0
Mar 26 08:13:01 localhost kernel: [<ffffffff8111f96d>] sync_page+0x3d/0x50
Mar 26 08:13:01 localhost kernel: [<ffffffff8152893a>] __wait_on_bit_lock+0x5a/0xc0
Mar 26 08:13:01 localhost kernel: [<ffffffff8111f907>] __lock_page+0x67/0x70
Mar 26 08:13:01 localhost kernel: [<ffffffff8109b320>] ? wake_bit_function+0x0/0x50
Mar 26 08:13:01 localhost kernel: [<ffffffff81135bf5>] ? pagevec_lookup_tag+0x25/0x40
Mar 26 08:13:01 localhost kernel: [<ffffffffa010db8f>] write_cache_pages_da+0x44f/0x470 [ext4]
Mar 26 08:13:01 localhost kernel: [<ffffffffa00df495>] ? jbd2_journal_start+0xb5/0x100 [jbd2]

最近服务器一直出现这种情况，直接卡死，看报错信息"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
于是就尝试把hung_task_timeout_secs的值改为0，修改核心的办法:
编辑sysctl.conf,在最后一行添加 kernel.hung_task_timeout_secs = 0
sysctl -p 立即生效，先试试观察一段时间。