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From: Andrea Righi <arighi@nvidia.com>
To: Peter Zijlstra <peterz@infradead.org>
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>,
	Shrikanth Hegde <sshegde@linux.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] sched/fair: Use guard(rcu) for sched_domain RCU sections
Date: Tue, 28 Apr 2026 15:16:53 +0200	[thread overview]
Message-ID: <afCzRVa57p0RFWGX@gpd4> (raw)
In-Reply-To: <20260428115017.GW3102624@noisy.programming.kicks-ass.net>

Hi Peter,

On Tue, Apr 28, 2026 at 01:50:17PM +0200, Peter Zijlstra wrote:
> 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.

Ah yes, indeed, I'll drop the lockdep_assert_irqs_disabled().

Thanks,
-Andrea

  reply	other threads:[~2026-04-28 13:17 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-28  5:16 [PATCH v4 0/6] sched/fair: SMT-aware asymmetric CPU capacity Andrea Righi
2026-04-28  5:16 ` [PATCH 1/6] sched/fair: Use guard(rcu) for sched_domain RCU sections Andrea Righi
2026-04-28  8:33   ` K Prateek Nayak
2026-04-28 10:43     ` Andrea Righi
2026-04-28 11:04       ` K Prateek Nayak
2026-04-28 11:50       ` Peter Zijlstra
2026-04-28 13:16         ` Andrea Righi [this message]
2026-04-28 14:12     ` Steven Rostedt
2026-04-28 14:26       ` Andrea Righi
2026-04-28 14:29         ` Steven Rostedt
2026-04-28  5:16 ` [PATCH 2/6] sched/fair: Attach sched_domain_shared to sd_asym_cpucapacity Andrea Righi
2026-04-28  6:45   ` Shrikanth Hegde
2026-04-28  8:47     ` Andrea Righi
2026-04-28  5:16 ` [PATCH 3/6] sched/fair: Prefer fully-idle SMT cores in asym-capacity idle selection Andrea Righi
2026-04-28  5:16 ` [PATCH 4/6] sched/fair: Reject misfit pulls onto busy SMT siblings on asym-capacity Andrea Righi
2026-04-28  5:16 ` [PATCH 5/6] sched/fair: Add SIS_UTIL support to select_idle_capacity() Andrea Righi
2026-04-28  5:16 ` [PATCH 6/6] sched/topology: Remove SMT/asym capacity warning Andrea Righi
2026-04-28  5:28   ` K Prateek Nayak
2026-04-28  5:54     ` Andrea Righi
2026-04-28  6:04       ` Andrea Righi

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