[PATCH v2 1/2] sched/cputime: Use only pi_lock to protect sum_exec_runtime read

[Stanislaw Gruszka <sgruszka@redhat.com>]

Currently we protect 64bit sum_exec_runtime read on 32bit cpus using
task_rq_lock() which internally takes t->pi_lock and rq->lock. Taking
rq->lock is not needed in this case.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
---
 kernel/sched/cputime.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index b93c72d..5535774 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -315,12 +315,11 @@ static inline u64 read_sum_exec_runtime(struct task_struct *t)
 static u64 read_sum_exec_runtime(struct task_struct *t)
 {
 	u64 ns;
-	struct rq_flags rf;
-	struct rq *rq;
+	unsigned long flags;
 
-	rq = task_rq_lock(t, &rf);
+	raw_spin_lock_irqsave(&t->pi_lock, flags);
 	ns = t->se.sum_exec_runtime;
-	task_rq_unlock(rq, t, &rf);
+	raw_spin_unlock_irqrestore(&t->pi_lock, flags);
 
 	return ns;
 }
-- 
1.8.3.1