I/O status of Process

http://kmaiti.blogspot.tw/2011/09/what-is-wchan-attribute-at-ps-alwww-on.html
http://askubuntu.com/questions/19442/what-is-the-waiting-channel-of-a-process

root@pjack-VirtualBox:~$ ps -alwww
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000   707   706  0  80   0 -  7014 wait   pts/7    00:00:00 bash
0 S  1000  2271   707  0  80   0 - 11950 poll_s pts/7    00:00:00 ssh
0 S  1000 25352 25248  0  80   0 -  4449 poll_s pts/6    00:00:00 tmux
0 S  1000 27179 27178  0  80   0 -  7012 wait   pts/4    00:00:00 bash
0 S  1000 27376 27179  0  80   0 - 10397 poll_s pts/4    00:00:00 ssh
4 R     0 27934 29703  0  80   0 -  3484 -      pts/5    00:00:00 ps
0 S  1000 29430 29429  0  80   0 -  7010 wait   pts/5    00:00:00 bash
4 S     0 29692 29430  0  80   0 - 15074 poll_s pts/5    00:00:00 sudo
4 S     0 29703 29692  0  80   0 -  6991 wait   pts/5    00:00:00 bash
0 S  1000 32224 32220  0  80   0 -  7056 n_tty_ pts/3    00:00:00 bash

root@pjack-VirtualBox:~$ cat /proc/707/wchan
do_wait
root@pjack-VirtualBox:~$ cat /proc/29692/wchan
poll_schedule_timeout

poll_schedule_timeout <= 等 I/O