Improve clarity in file access example

Replaced "vt" with "virtual terminal" to improve readability,
as the abbreviation appears for the first time in this section.
Also rephrased to avoid nested parentheses.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>

lkmpg.tex

@@ -1612,7 +1612,8 @@ The process does not know somebody else used the CPU for most of the time betwee
 It can then proceed to set a global variable to tell all the other processes that the file is still open and go on with its life.
 When the other processes get a piece of the CPU, they'll see that global variable and go back to sleep.
 
-So we will use \sh|tail -f| to keep the file open in the background, while trying to access it with another process (again in the background, so that we need not switch to a different vt).
+So we will use \sh|tail -f| to keep the file open in the background, and attempt to access it with another background process.
+This way, we don't need to switch to another terminal window or virtual terminal to run the second process.
 As soon as the first background process is killed with kill \%1 , the second is woken up, is able to access the file and finally terminates.
 
 To make our life more interesting, \cpp|module_close| does not have a monopoly on waking up the processes which wait to access the file.