sched/deadline: Show leftover runtime and abs deadline in /proc/*/sched

This patch allows for reading the current (leftover) runtime and
absolute deadline of a SCHED_DEADLINE task through /proc/*/sched
(entries dl.runtime and dl.deadline), while debugging/testing.

Signed-off-by: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
Reviewed-by: Luca Abeni <luca.abeni@unitn.it>
Acked-by: Daniel Bistrot de Oliveira <danielbristot@gmail.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1477473437-10346-2-git-send-email-tommaso.cucinotta@sssup.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/scheduler/sched-deadline.txt

@@ -408,6 +408,11 @@ CONTENTS
   * the new scheduling related syscalls that manipulate it, i.e.,
     sched_setattr() and sched_getattr() are implemented.
 
+ For debugging purposes, the leftover runtime and absolute deadline of a
+ SCHED_DEADLINE task can be retrieved through /proc/<pid>/sched (entries
+ dl.runtime and dl.deadline, both values in ns). A programmatic way to
+ retrieve these values from production code is under discussion.
+
 
 4.3 Default behavior
 ---------------------
@@ -476,6 +481,7 @@ CONTENTS
 
  Still missing:
 
+  - programmatic way to retrieve current runtime and absolute deadline
   - refinements to deadline inheritance, especially regarding the possibility
     of retaining bandwidth isolation among non-interacting tasks. This is
     being studied from both theoretical and practical points of view, and

kernel/sched/debug.c

@@ -953,6 +953,10 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
 #endif
 	P(policy);
 	P(prio);
+	if (p->policy == SCHED_DEADLINE) {
+		P(dl.runtime);
+		P(dl.deadline);
+	}
 #undef PN_SCHEDSTAT
 #undef PN
 #undef __PN