Hi!
I'm using ftrace in order to trace any task or process running. I'm interesting to the context switch tracing. Ok, I've enabled sched_switch and the results are in the trace file.
How can I interpretate correctly the results?
What does the following mean?

bash-3997 [01] 240.132281: 3997:120:R + 4055:120:R

The process 3997 (pid) with priority 120 is runnnig (R), right?
At the time 240.132281 the process 4055 wake up and....
What does the R of the process 4055 mean?

bash-3997 [01] 240.132284: 3997:120:R ==> 4055:120:R

This is a real context witch, I suppose. Why is 3997 still running?
I believe that if there's a context switch, like in this case, the
process 3997 should sleep and 4055 starts to run.

sleep-4055 [01] 240.132371: 4055:120:S ==> 3997:120:R

This is the case that I said above, right?

bash-3997 [01] 240.132454: 3997:120:R + 4055:120:S

4005 wake up and it goes to sleep, right?

sleep-4055 [01] 240.132460: 4055:120: D ==> 3997:120:R

What is D?

bash-3997 [01] 240.132463: 3997:120:R + 4055:120: D

4005 wakes up and goes in the state.... I don't know

The documentation says that the R state is:
the process wants to run, may not actually be running.
Is it running or not? How can I know if it's running?

Help me.
Thanks

D state means that process must be woken up. orginal message of D abbreviation is Disk Sleep(uninterruptible sleep).