task php-fpm:*** blocked for more than 120 seconds

系统出现问题，在/var/log/messages文件里有如下信息：
May 27 10:29:58 ID17342 kernel: INFO: task php-fpm:18480 blocked for more than 120 seconds.
May 27 10:29:58 ID17342 kernel:      Not tainted 2.6.32-431.11.2.el6.x86_64 #1
May 27 10:29:58 ID17342 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 27 10:29:58 ID17342 kernel: php-fpm       D 0000000000000000     0 18480  31836 0x00000000
May 27 10:29:58 ID17342 kernel: ffff880415b45e38 0000000000000086 ffff880415b45da8 ffffffff811863b4
May 27 10:29:58 ID17342 kernel: 0000000000098800 0000000000098800 ffff880415b45f18 ffffffff8119bc0a
May 27 10:29:58 ID17342 kernel: ffff88022aa2e5f8 ffff880415b45fd8 000000000000fbc8 ffff88022aa2e5f8
May 27 10:29:58 ID17342 kernel: Call Trace:
May 27 10:29:58 ID17342 kernel: [] ? nameidata_to_filp+0x54/0x70
May 27 10:29:58 ID17342 kernel: [] ? do_filp_open+0x6ea/0xd20
May 27 10:29:58 ID17342 kernel: [] rwsem_down_failed_common+0x95/0x1d0
May 27 10:29:58 ID17342 kernel: [] ? cp_new_stat+0xe4/0x100
May 27 10:29:58 ID17342 kernel: [] rwsem_down_write_failed+0x23/0x30
May 27 10:29:58 ID17342 kernel: [] call_rwsem_down_write_failed+0x13/0x20
May 27 10:29:58 ID17342 kernel: [] ? down_write+0x32/0x40
May 27 10:29:58 ID17342 kernel: [] sys_brk+0x40/0x130
May 27 10:29:58 ID17342 kernel: [] system_call_fastpath+0x16/0x1b
如附件所示：

解决方法：
在/etc/sysctl.conf中加入：
vm.dirty_ratio=10
然后执行sysctl -p 使其立即生效
问题即可解决