Re: [GIT PULL rcu/next] RCU commits for 3.3

[Suresh Siddha <suresh.b.siddha@intel.com>]

On Wed, 2011-12-14 at 09:47 -0800, Frederic Weisbecker wrote:
> I don't know how you plan to fix the conflict, by redoing the merge or by
> applying a patch on tip/master.
> 
> In any case, here is a patch you can use. Feel free to apply it as is
> or to just refer to its diff to redo the merge:
> 
> (Outrageously only compile tested)
> 
> ---
> From: Frederic Weisbecker <fweisbec@gmail.com>
> Date: Wed, 14 Dec 2011 18:36:00 +0100
> Subject: [PATCH] sched: Only update the CPU idleness in the domain
>  hierarchy from idle loop entry
> 
> We don't need to inform the sched domain hierarchy about the
> CPU idleness everytime we call tick_nohz_stop_sched_tick() as this
> includes both idle loop entry and idle interrupt exit.
> 
> Doing it once from the idle loop entry is enough, call
> set_cpu_sd_state_idle() only from tick_nohz_idle_enter() instead
> to fix this.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Suresh Siddha <suresh.b.siddha@intel.com>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>

Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>

> ---
>  kernel/time/tick-sched.c |   16 ++++++++--------
>  1 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index 1f6dc515..696c997 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -289,14 +289,6 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
>         now = tick_nohz_start_idle(cpu, ts);
> 
>         /*
> -        * Update the idle state in the scheduler domain hierarchy
> -        * when tick_nohz_stop_sched_tick() is called from the idle loop.
> -        * State will be updated to busy during the first busy tick after
> -        * exiting idle.
> -        */
> -       set_cpu_sd_state_idle();
> -
> -       /*
>          * If this cpu is offline and it is the one which updates
>          * jiffies, then give up the assignment and let it be taken by
>          * the cpu which runs the tick timer next. If we don't drop
> @@ -483,6 +475,14 @@ void tick_nohz_idle_enter(void)
>          * update of the idle time accounting in tick_nohz_start_idle().
>          */
>         ts->inidle = 1;
> +
> +       /*
> +        * Update the idle state in the scheduler domain hierarchy
> +        * when tick_nohz_idle_enter() is called from the idle loop.
> +        * State will be updated to busy during the first busy tick after
> +        * exiting idle.
> +        */
> +       set_cpu_sd_state_idle();
>         tick_nohz_stop_sched_tick(ts);
> 
>         local_irq_enable();
> --
> 1.7.5.4
> 
>