rq lock in task_sched_runtime() is necessary for two reasons. 1)
accessing se.sum_exec_runtime is inatomic on 32bit and 2)
do_task_delta_exec() require it.
And then, 64bit can avoid holds rq lock when add_delta is false.
Signed-off-by: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com>
---
kernel/sched/core.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b817e6d..24ba1c6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2657,6 +2657,12 @@ unsigned long long task_sched_runtime(struct task_struct
*p, bool add_delta)
struct rq *rq;
u64 ns = 0;
+ /* Micro optimization. */
+#ifdef CONFIG_64BIT
+ if (!add_delta)
+ return p->se.sum_exec_runtime;
+#endif
+
rq = task_rq_lock(p, &flags);
ns = p->se.sum_exec_runtime;
if (add_delta)
--
1.7.1
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