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SubjectRe: [PATCH tip/core/rcu 22/30] rcu: Don't flag non-starting GPs before GP kthread is running
On Fri, 14 Feb 2020 15:55:59 -0800
paulmck@kernel.org wrote:

> @@ -1252,10 +1252,10 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
> */
> static void rcu_gp_kthread_wake(void)
> {
> - if ((current == rcu_state.gp_kthread &&
> + if ((current == READ_ONCE(rcu_state.gp_kthread) &&
> !in_irq() && !in_serving_softirq()) ||
> !READ_ONCE(rcu_state.gp_flags) ||
> - !rcu_state.gp_kthread)
> + !READ_ONCE(rcu_state.gp_kthread))
> return;

This looks buggy. You have two instances of
READ_ONCE(rcu_state.gp_thread), which means they can be different. Is
that intentional?

-- Steve

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