Re: [PATCH] sched: Remove broken check for skip clock update
2013/1/8 Steven Rostedt : > 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; Grr, I knew I was missing something! Ok let's drop that patch then. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] sched: Remove broken check for skip clock update
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
> Cc: Ingo Molnar
> Cc: Peter Zijlstra
> Cc: Steven Rostedt
> ---
> 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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[PATCH] sched: Remove broken check for skip clock update
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.
Signed-off-by: Frederic Weisbecker
Cc: Ingo Molnar
Cc: Peter Zijlstra
Cc: Steven Rostedt
---
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);
}
--
1.7.5.4
--
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