sched/deadline: Fix the description of runtime accounting in the documentation

Signed-off-by: Claudio Scordino <claudio@evidence.eu.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/1510658366-28995-1-git-send-email-claudio@evidence.eu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/scheduler/sched-deadline.txt

@@ -204,10 +204,17 @@ CONTENTS
  It does so by decrementing the runtime of the executing task Ti at a pace equal
  to
 
-           dq = -max{ Ui, (1 - Uinact) } dt
+           dq = -max{ Ui / Umax, (1 - Uinact - Uextra) } dt
 
- where Uinact is the inactive utilization, computed as (this_bq - running_bw),
- and Ui is the bandwidth of task Ti.
+ where:
+
+  - Ui is the bandwidth of task Ti;
+  - Umax is the maximum reclaimable utilization (subjected to RT throttling
+    limits);
+  - Uinact is the (per runqueue) inactive utilization, computed as
+    (this_bq - running_bw);
+  - Uextra is the (per runqueue) extra reclaimable utilization
+    (subjected to RT throttling limits).
 
 
  Let's now see a trivial example of two deadline tasks with runtime equal