Re: [PATCH] rcu/tree: Force quiescent state on callback overload

From: Paul E. McKenney
Date: Sun Jun 21 2020 - 15:51:00 EST


On Mon, Jun 22, 2020 at 12:07:27AM +0530, Neeraj Upadhyay wrote:
> On callback overload, we want to force quiescent state immediately,
> for the first and second fqs. Enforce the same, by including
> RCU_GP_FLAG_OVLD flag, in fqsstart check.
>
> Signed-off-by: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>

Good catch!

But what did you do to verify that this change does the right thing?

Thanx, Paul

> ---
> kernel/rcu/tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index d0988a1..6226bfb 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1865,7 +1865,7 @@ static void rcu_gp_fqs_loop(void)
> break;
> /* If time for quiescent-state forcing, do it. */
> if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
> - (gf & RCU_GP_FLAG_FQS)) {
> + (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
> trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
> TPS("fqsstart"));
> rcu_gp_fqs(first_gp_fqs);
> --
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