On Tue, Jan 17, 2023 at 10:19:55AM +0800, Zqiang wrote:
> When inovke rcu_report_qs_rdp(), if current CPU's rcu_data structure's ->
> grpmask has not been cleared from the corresponding rcu_node structure's
> ->qsmask, after that will clear and report quiescent state, but in this
> time, this also means that current grace period is not end, the current
> grace period is ongoing, because the rcu_gp_in_progress() currently return
> true, so for non-offloaded rdp, invoke rcu_accelerate_cbs() is impossible
> to return true.
>
> This commit therefore remove impossible rcu_gp_kthread_wake() calling.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
> ---
> kernel/rcu/tree.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index b2c204529478..477eb1a374e5 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1956,7 +1956,6 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
> {
> unsigned long flags;
> unsigned long mask;
> - bool needwake = false;
> bool needacc = false;
> struct rcu_node *rnp;
>
> @@ -1988,7 +1987,7 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
> * NOCB kthreads have their own way to deal with that...
> */
> if (!rcu_rdp_is_offloaded(rdp)) {
> - needwake = rcu_accelerate_cbs(rnp, rdp);
> + rcu_accelerate_cbs(rnp, rdp);
>
>If it is impossible, we should use WARN_ON_ONCE() or similar. Just
>in case the system disagrees on the impossibility. ;-)
Thanks for suggestion, I will resend v2 😊.
>
> Thanx, Paul
> } else if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
> /*
> * ...but NOCB kthreads may miss or delay callbacks acceleration
> @@ -2000,8 +1999,6 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
> rcu_disable_urgency_upon_qs(rdp);
> rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
> /* ^^^ Released rnp->lock */
> - if (needwake)
> - rcu_gp_kthread_wake();
>
> if (needacc) {
> rcu_nocb_lock_irqsave(rdp, flags);
> --
> 2.25.1
>
