On Tue, 2013-01-08 at 02:07 +0100, Frederic Weisbecker wrote:
> rq->skip_clock_update shouldn't be negative. Thus the check
> in put_prev_task() is useless.
>
> It was probably intended to do the following check:
>
> if (prev->on_rq && !rq->skip_clock_update)
>
> We only want to update the clock if the current task is
> not voluntarily sleeping: otherwise deactivate_task()
> already did the rq clock update in schedule(). But we want
> to ignore that update if a ttwu did it for us, in which case
> rq->skip_clock_update is 1.
>
> But update_rq_clock() already takes care of that so we
> can just remove the broken condition.
kernel/sched/rt.c:
/*
* Force a clock update if the CPU was idle,
* lest wakeup -> unthrottle time accumulate.
*/
if (rt_rq->rt_nr_running && rq->curr ==
rq->idle)
rq->skip_clock_update = -1;
-- Steve
>
> Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Steven Rostedt <rost...@goodmis.org>
> ---
> kernel/sched/core.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 15ba35e..8dfc461 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2886,7 +2886,7 @@ static inline void schedule_debug(struct task_struct
> *prev)
>
> static void put_prev_task(struct rq *rq, struct task_struct *prev)
> {
> - if (prev->on_rq || rq->skip_clock_update < 0)
> + if (prev->on_rq)
> update_rq_clock(rq);
> prev->sched_class->put_prev_task(rq, prev);
> }
--
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