Is the following an accurate statement for current versions of Linux?

"The cumulative cpu usage of a process and all of its descendents at a
given instant of time can be obtained by summing together the utime
and stime fields in the /proc//stat files for the process and all
of its descendents. For example, if process 100 has 2 children 101 and
102, and process 102 has two children 104 and 108, and at a given
instant the utime and stime fields for the processes look like

pid utime stime
100 0 0
101 12 1
102 14 2
104 1 3
108 2 0

then the amount of cpu time taken by process 100 and all of its
descendents is 35 jiffies. (This assumes that the processes listed did
not fork any other processes.)"


The reason I am asking is that it seems rather tricky to get _current_
cpu usage for a process and all of its descendents in Linux; examining
the /proc//stat file seems the only reliable way. I just want to
be sure I understand the situation properly.

Thanks.