On Sat, Nov 21, 2015 at 01:02:02AM -0800, Lianwei Wang wrote:
> The rcu_idle_endter may call wakeup_softirqd to set the need resched
> flag on idle process. But if we don't check it after that, then the
> cpu will enter idle state with RESCHED flag set and can not be woken
> up by wakeup/resched call anymore.
>
> Check need_resched after rcu_idle_enter to make sure the cpu is able
> to be out of idle immediatley to run other tasks.
>
> Signed-off-by: Lianwei Wang <lianwei.wang@xxxxxxxxx>
> ---
> kernel/sched/idle.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 4a2ef5a02fd3..6e96a1f41041 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -137,21 +137,21 @@ static void cpuidle_idle_call(void)
> int next_state, entered_state;
>
> /*
> + * Tell the RCU framework we are entering an idle section,
> + * so no more rcu read side critical sections and one more
> + * step to the grace period
> + */
> + rcu_idle_enter();
> +
> + /*
> * Check if the idle task must be rescheduled. If it is the
> * case, exit the function after re-enabling the local irq.
> */
> if (need_resched()) {
> local_irq_enable();
> - return;
> + goto exit_idle;
> }
>
> - /*
> - * Tell the RCU framework we are entering an idle section,
> - * so no more rcu read side critical sections and one more
> - * step to the grace period
> - */
> - rcu_idle_enter();
> -
> if (cpuidle_not_available(drv, dev)) {
> default_idle_call();
> goto exit_idle;
FWIW your patch is whitespace mangled; I could not apply if I wanted to.
