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

[Paul E. McKenney]

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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