XMonad locks up by my window still works

I’ve just recently installed XMonad on my laptop and am just ironing out some issues that have popped up from time to time. Today, I’d noticed that XMonad had stopped responding to my mod key requests, however the focused application (in my case firefox) was still responding.

After doing some searching around the web, I’ve come across this article which has set me straight. It seems that a pipe that XMonad writes to is full - it just needs to be cleared.

First off, you’ll need to get yourelf to a terminal. If you’re unable to do that (like I was), I went to another virtual terminal all together by using alt+ctrl+f1.

You need to find XMonad’s currently running pid.

$ ps -ef | grep xmonad
michael  1406  1395  0 10:48 ?      00:00:09 /home/michael/.xmonad/xmonad-x86_64-linux

In my case, it’s 1406. You need to take a look at this pid’s file descriptors:

$ ls -l /proc/1406/fd
total 0
lr-x------ 1 michael michael 64 Jun 18 14:10 0 -> /dev/null
lrwx------ 1 michael michael 64 Jun 18 14:10 1 -> socket:[17946]
lrwx------ 1 michael michael 64 Jun 18 14:10 2 -> socket:[17946]
l-wx------ 1 michael michael 64 Jun 18 14:10 3 -> /var/log/slim.log
lrwx------ 1 michael michael 64 Jun 18 14:10 4 -> socket:[18899]
l-wx------ 1 michael michael 64 Jun 18 14:10 5 -> pipe:[18898]

So, in my case here #5 which is the pipe - needs to be cleared. You can do so really quickly just by catting it to screen.

$ cat /proc/1406/fd

XMonad should now be back in the land of the living.

Finally, this should never be a problem just as long as your xmonad.hs is configured with a logHook that will pipe the contents of this stream out.

xmproc <- spawnPipe "xmobar"

. . .
. . .

logHook = dynamicLogWithPP $ xmobarPP
         { ppOutput = hPutStrLn xmproc
         , ppTitle = xmobarColor "green" "" . shorten 50
         }