linux-kernel - Re: [PATCH] rcu/tree: Fix self wakeups for grace period kthread

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Date:   Mon, 11 Mar 2019 21:50:27 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Neeraj Upadhyay <neeraju@...eaurora.org>
Cc:     paulmck@...ux.vnet.ibm.com, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu/tree: Fix self wakeups for grace period kthread

On Fri,  8 Mar 2019 15:16:18 +0530
Neeraj Upadhyay <neeraju@...eaurora.org> wrote:

> Update the code to match the comment that self wakeup of
> grace period kthread is allowed from interrupt handler, and
> softirq handler, running in the grace period kthread's
> context. Present code allows self wakeups from all
> interrupt contexts - nmi, softirq and hardirq contexts.

That's not actually the issue. But it appears that we return if we
simply have BH disabled, which I don't think we want, and we don't care
about NMI as NMI should never call this code.

I think your patch is correct, but the change log is not.

-- Steve


> 
> Signed-off-by: Neeraj Upadhyay <neeraju@...eaurora.org>
> ---
>  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 acd6ccf..57cac6d 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1585,7 +1585,7 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
>  static void rcu_gp_kthread_wake(void)
>  {
>  	if ((current == rcu_state.gp_kthread &&
> -	     !in_interrupt() && !in_serving_softirq()) ||
> +	     !in_irq() && !in_serving_softirq()) ||
>  	    !READ_ONCE(rcu_state.gp_flags) ||
>  	    !rcu_state.gp_kthread)
>  		return;