sched/rt: Make update_curr_rt() more accurate

rq->clock_task may be updated between the two calls of
rq_clock_task() in update_curr_rt(). Calling rq_clock_task() only
once makes it more accurate and efficient, taking update_curr() as
reference.

Signed-off-by: Wen Yang <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Jiang Biao <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 663b2355a3aa772d8bcc8c90b55a3e0e0e3a6e17..aad49451584e6766d1b9a2f657397da345146c23 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -950,12 +950,13 @@ static void update_curr_rt(struct rq *rq)
 {
        struct task_struct *curr = rq->curr;
        struct sched_rt_entity *rt_se = &curr->rt;
-       u64 now = rq_clock_task(rq);
        u64 delta_exec;
+       u64 now;
 
        if (curr->sched_class != &rt_sched_class)
                return;
 
+       now = rq_clock_task(rq);
        delta_exec = now - curr->se.exec_start;
        if (unlikely((s64)delta_exec <= 0))
                return;