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sched/core: Simplify update_rq_clock() in __schedule() 

Instead of relying on deactivate_task() to call update_rq_clock() and
handling the case where it didn't happen (task_on_rq_queued),
unconditionally do update_rq_clock() and skip any further updates.

This also avoids a double update on deactivate_task() + ttwu_local().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-02-21 14:40:35 +01:00 committed by Ingo Molnar
parent 77558e4d01
commit bce4dc80c6
1 changed files with 3 additions and 5 deletions
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8
kernel/sched/core.c
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@ -2114,7 +2114,7 @@ static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf)
delayacct_blkio_end();
atomic_dec(&rq->nr_iowait);
}
ttwu_activate(rq, p, ENQUEUE_WAKEUP);
ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK);
}
ttwu_do_wakeup(rq, p, 0, rf);
@ -3393,13 +3393,14 @@ static void __sched notrace __schedule(bool preempt)
/* Promote REQ to ACT */
rq->clock_update_flags <<= 1;
update_rq_clock(rq);
switch_count = &prev->nivcsw;
if (!preempt && prev->state) {
if (unlikely(signal_pending_state(prev->state, prev))) {
prev->state = TASK_RUNNING;
} else {
deactivate_task(rq, prev, DEQUEUE_SLEEP);
deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
prev->on_rq = 0;
if (prev->in_iowait) {
@ -3423,9 +3424,6 @@ static void __sched notrace __schedule(bool preempt)
switch_count = &prev->nvcsw;
}
if (task_on_rq_queued(prev))
update_rq_clock(rq);
next = pick_next_task(rq, prev, &rf);
clear_tsk_need_resched(prev);
clear_preempt_need_resched();