From: Peter Zijlstra <peterz@infradead.org>
To: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>,
Vishal Chourasia <vishalc@linux.ibm.com>,
boqun.feng@gmail.com, frederic@kernel.org, josh@joshtriplett.org,
linux-kernel@vger.kernel.org, neeraj.upadhyay@kernel.org,
paulmck@kernel.org, rcu@vger.kernel.org, rostedt@goodmis.org,
srikar@linux.ibm.com, tglx@linutronix.de, urezki@gmail.com,
samir@linux.ibm.com
Subject: Re: [PATCH] cpuhp: Expedite synchronize_rcu during SMT switch
Date: Mon, 19 Jan 2026 15:59:38 +0100 [thread overview]
Message-ID: <20260119145938.GJ831050@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <DS0PR12MB6486E6599B99D08C5E46EC06A388A@DS0PR12MB6486.namprd12.prod.outlook.com>
On Mon, Jan 19, 2026 at 09:45:48AM -0500, Joel Fernandes wrote:
> On Sun, Jan 19, 2026 at 03:11:18PM +0100, Peter Zijlstra wrote:
> > By holding an extra rcu_sync reference, the percpu rwsem is kept into
> > the the slow path, avoiding the rcu-sync on down_write(), which was very
> > prevalent per this:
> >
> > https://lkml.kernel.org/r/aWU9HRcs4ghazIRg@linux.ibm.com
>
> Makes sense, though I wonder if we should have a separate percpu-rwsem API
> for this rather than directly accessing the lock-internal rcu_sync state?
> Other future percpu_rw_semaphore users may benefit as well.
Yeah, perhaps. There is one other user, the above makes two.
kernel/cgroup/cgroup.c: rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
next prev parent reply other threads:[~2026-01-19 14:59 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-12 9:43 [PATCH] cpuhp: Expedite synchronize_rcu during CPU hotplug operations Vishal Chourasia
2026-01-12 10:08 ` Uladzislau Rezki
2026-01-12 10:43 ` Vishal Chourasia
2026-01-12 11:07 ` Uladzislau Rezki
2026-01-12 12:02 ` Shrikanth Hegde
2026-01-12 12:57 ` Uladzislau Rezki
2026-01-12 16:09 ` Joel Fernandes
2026-01-12 16:48 ` Paul E. McKenney
2026-01-12 17:05 ` Uladzislau Rezki
2026-01-12 18:27 ` Vishal Chourasia
2026-01-13 0:03 ` Paul E. McKenney
2026-01-12 22:24 ` Joel Fernandes
2026-01-13 0:01 ` Paul E. McKenney
2026-01-13 2:46 ` Joel Fernandes
2026-01-13 4:53 ` Shrikanth Hegde
2026-01-13 8:57 ` Joel Fernandes
2026-01-14 4:00 ` Paul E. McKenney
2026-01-14 8:54 ` Joel Fernandes
2026-01-16 19:02 ` Paul E. McKenney
2026-01-14 3:59 ` Paul E. McKenney
2026-01-12 17:09 ` Uladzislau Rezki
2026-01-12 17:36 ` Joel Fernandes
2026-01-13 12:18 ` Uladzislau Rezki
2026-01-13 12:44 ` Joel Fernandes
2026-01-13 14:17 ` Uladzislau Rezki
2026-01-13 14:32 ` Joel Fernandes
2026-01-13 14:53 ` Shrikanth Hegde
2026-01-13 18:17 ` Uladzislau Rezki
2026-01-13 17:58 ` Uladzislau Rezki
2026-01-12 12:21 ` Shrikanth Hegde
2026-01-12 12:46 ` Vishal Chourasia
2026-01-12 14:03 ` Joel Fernandes
2026-01-12 14:20 ` Joel Fernandes
2026-01-12 14:23 ` Peter Zijlstra
2026-01-12 14:37 ` Joel Fernandes
2026-01-12 17:52 ` Vishal Chourasia
2026-01-12 14:24 ` Peter Zijlstra
2026-01-12 18:00 ` Vishal Chourasia
2026-01-13 9:01 ` Peter Zijlstra
2026-01-19 10:47 ` [PATCH] cpuhp: Expedite synchronize_rcu during SMT switch Vishal Chourasia
2026-01-19 11:43 ` Peter Zijlstra
2026-01-19 13:45 ` Shrikanth Hegde
2026-01-19 14:11 ` Peter Zijlstra
2026-01-19 14:45 ` Joel Fernandes
2026-01-19 14:59 ` Peter Zijlstra [this message]
2026-01-27 17:48 ` Samir M
2026-01-29 7:05 ` Samir M
2026-02-03 6:31 ` Samir M
2026-01-19 10:54 ` [RESEND] " Vishal Chourasia
2026-01-18 11:38 ` [PATCH] cpuhp: Expedite synchronize_rcu during CPU hotplug operations Samir M
2026-01-19 5:18 ` Joel Fernandes
2026-01-19 13:53 ` Shrikanth Hegde
2026-01-19 21:10 ` joelagnelf
2026-02-02 8:46 ` Vishal Chourasia
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