commit 7098c1eac75dc03fdbb7249171a6e68ce6044a5a
author Frederic Weisbecker <fweisbec@gmail.com> Thu Nov 19 16:47:30 2015 +0100
committer Ingo Molnar <mingo@kernel.org> Fri Dec 04 10:34:44 2015 +0100
tree 06b4c828297c06b6aaa5494054a5cb9855e2d198
parent 7877a0ba5ec63c7b0111b06c773f1696fa17b35a

sched/cputime: Clarify vtime symbols and document them

VTIME_SLEEPING state happens either when:

1) The task is sleeping and no tickless delta is to be added on the task
   cputime stats.
2) The CPU isn't running vtime at all, so the same properties of 1) applies.

Lets rename the vtime symbol to reflect both states.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447948054-28668-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f425aac..3533168 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1522,8 +1522,11 @@
 	seqlock_t vtime_seqlock;
 	unsigned long long vtime_snap;
 	enum {
-		VTIME_SLEEPING = 0,
+		/* Task is sleeping or running in a CPU with VTIME inactive */
+		VTIME_INACTIVE = 0,
+		/* Task runs in userspace in a CPU with VTIME active */
 		VTIME_USER,
+		/* Task runs in kernelspace in a CPU with VTIME active */
 		VTIME_SYS,
 	} vtime_snap_whence;
 #endif

kernel/fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index f97f2c4..c0a1370 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1350,7 +1350,7 @@
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
 	seqlock_init(&p->vtime_seqlock);
 	p->vtime_snap = 0;
-	p->vtime_snap_whence = VTIME_SLEEPING;
+	p->vtime_snap_whence = VTIME_INACTIVE;
 #endif
 
 #if defined(SPLIT_RSS_COUNTING)

kernel/sched/cputime.c

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 1128d4b..4a18a6e 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -680,7 +680,7 @@
 {
 	unsigned long long delta = vtime_delta(tsk);
 
-	WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_SLEEPING);
+	WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
 	tsk->vtime_snap += delta;
 
 	/* CHECKME: always safe to convert nsecs to cputime? */
@@ -764,7 +764,7 @@
 void arch_vtime_task_switch(struct task_struct *prev)
 {
 	write_seqlock(&prev->vtime_seqlock);
-	prev->vtime_snap_whence = VTIME_SLEEPING;
+	prev->vtime_snap_whence = VTIME_INACTIVE;
 	write_sequnlock(&prev->vtime_seqlock);
 
 	write_seqlock(&current->vtime_seqlock);
@@ -829,7 +829,7 @@
 			*s_dst = *s_src;
 
 		/* Task is sleeping, nothing to add */
-		if (t->vtime_snap_whence == VTIME_SLEEPING ||
+		if (t->vtime_snap_whence == VTIME_INACTIVE ||
 		    is_idle_task(t))
 			continue;