Re: [PATCH -rcu dev 2/3] rcu/tree: Fix issue where sometimes rcu_urgent_qs is not set on IPI

[Joel Fernandes]

On Thu, Aug 15, 2019 at 10:53:10PM -0400, Joel Fernandes (Google) wrote:
> Sometimes I see rcu_urgent_qs is not set. This could be when the last
> IPI was a long time ago, however, the grace period just started. Set
> rcu_urgent_qs so the tick can indeed be stopped.
Here I meant:
   not be stopped.

I will resend the patch as v2.
thanks,

 - Joel


> 
> Signed-off-by: Joel Fernandes (Google) 
> ---
>  kernel/rcu/tree.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 322b1b57967c..856d3c9f1955 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1091,6 +1091,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data 
> *rdp)
>   if (tick_nohz_full_cpu(rdp->cpu) &&
>  time_after(jiffies,
> READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
> + WRITE_ONCE(*ruqp, true);
>   resched_cpu(rdp->cpu);
>   WRITE_ONCE(rdp->last_fqs_resched, jiffies);
>   }
> -- 
> 2.23.0.rc1.153.gdeed80330f-goog
> 

[PATCH -rcu dev 2/3] rcu/tree: Fix issue where sometimes rcu_urgent_qs is not set on IPI

[Joel Fernandes (Google)]

Sometimes I see rcu_urgent_qs is not set. This could be when the last
IPI was a long time ago, however, the grace period just started. Set
rcu_urgent_qs so the tick can indeed be stopped.

Signed-off-by: Joel Fernandes (Google) 
---
 kernel/rcu/tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 322b1b57967c..856d3c9f1955 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1091,6 +1091,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
if (tick_nohz_full_cpu(rdp->cpu) &&
   time_after(jiffies,
  READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
+   WRITE_ONCE(*ruqp, true);
resched_cpu(rdp->cpu);
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
}
-- 
2.23.0.rc1.153.gdeed80330f-goog