linux-kernel - Re: [PATCH] rcu/sync: kill rcu_sync_type/gp

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Date:   Wed, 24 Apr 2019 13:37:04 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu/sync: kill rcu_sync_type/gp_type

On 04/23, Paul E. McKenney wrote:
>
> I wordsmithed the commit log and merged in the RCU-bh and RCU checks
> to rcu_sync_is_idle(), with the result shown below.  Does that work
> OK, or did I mess something up?

Yes, thanks!

the additional RCU-bh and RCU checks matches the "or introduce rcu_read_lock_any_held()"
note from the changelog, perhaps it makes some sense...

Just one nit below,

> - * Must be invoked within an RCU read-side critical section whose
> - * flavor matches that of the rcu_sync struture.
> + * Must be invoked within an RCU-sched read-side critical section.
                                ^^^^^^^^^

Given that the actual code:

>  static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
>  {
> -#ifdef CONFIG_PROVE_RCU
> -	rcu_sync_lockdep_assert(rsp);
> -#endif
> +	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
> +			 !rcu_read_lock_bh_held() &&
> +			 !rcu_read_lock_sched_held(),
> +			 "suspicious rcu_sync_is_idle() usage");

does RCU_LOCKDEP_WARN(!rcu_read_lock_any()) the comment should say

	Must be invoked within an RCU read-side critical section of
	any flavor

?

Oleg.