netdev - Re: [PATCH] net: raise RCU qs after each threaded NAPI poll

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Date: Thu, 7 Mar 2024 10:58:40 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Mark Rutland <mark.rutland@....com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, rcu@...r.kernel.org,
	kernel-team <kernel-team@...udflare.com>
Subject: Re: [PATCH] net: raise RCU qs after each threaded NAPI poll

On Thu, Mar 07, 2024 at 01:52:15PM -0500, Steven Rostedt wrote:
> On Thu, 7 Mar 2024 16:57:33 +0000
> Mark Rutland <mark.rutland@....com> wrote:
> 
> > * Use rcu_tasks_trace to synchronize updates?
> 
> Yes. I think I wanted both. The above to make sure it covers all cases
> where something could be preempted, and a case for those covered when RCU
> isn't watching (which always has preemption disabled).
> 
> My mistake was I thought synchronize_rcu_tasks_rude() did both. But I just
> found out recently that it is not a superset of synchronize_rcu_tasks().
> 
> But it really needs it in every location that synchronize_rcu_tasks_rude()
> is called.

Should any RCU Tasks Rude grace-period request also wait for an RCU Tasks
grace period?

I would feel better about proposing this, especially for
call_rcu_tasks_rude(), if RCU Tasks Rude was not supposed to be going
away after all the noinstr tags are in place.

							Thanx, Paul