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Date: Tue, 28 Apr 2026 13:50:17 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>,
	Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	Christian Loehle <christian.loehle@arm.com>,
	Koba Ko <kobak@nvidia.com>, Felix Abecassis <fabecassis@nvidia.com>,
	Balbir Singh <balbirs@nvidia.com>,
	Joel Fernandes <joelagnelf@nvidia.com>,
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	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] sched/fair: Use guard(rcu) for sched_domain RCU
 sections
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References: <20260428051720.3180182-1-arighi@nvidia.com>
 <20260428051720.3180182-2-arighi@nvidia.com>
 <0882ce78-a51f-4317-a1b4-624e39e65507@amd.com>
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In-Reply-To: <afCPSnkepnRqzWdt@gpd4>

On Tue, Apr 28, 2026 at 12:43:22PM +0200, Andrea Righi wrote:

> > and since this is only called from:
> > 
> >   sched_tick() /* IRQs disabled */
> >     sched_balance_trigger()
> >       nohz_balancer_kick()
> > 
> > with IRQs disabled, we can get rid of that rcu_read_lock() entirely.
> 
> Yeah, all makes sense. I'll update the patch dropping rcu_read_lock/unlock()
> completely.
> 
> Is it worth adding a lockdep_assert_irqs_disabled()?

I think the rcu_dereference_all() thing will go scream if it doesn't
have any of IRQs/preempt/rcu disabled.