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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: David Woodhouse <dwmw2@infradead.org>,
	"Paul E . McKenney" <paulmck@kernel.org>
Cc: linux-kernel@vger.kernel.org,
	Frederic Weisbecker <frederic@kernel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
	Joel Fernandes <joelagnelf@nvidia.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Boqun Feng <boqun@kernel.org>,
	Uladzislau Rezki <urezki@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Zqiang <qiang.zhang@linux.dev>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Kunwu Chan <kunwu.chan@gmail.com>,
	Puranjay Mohan <puranjay@kernel.org>,
	rcu@vger.kernel.org
Subject: Re: [PATCH v2 0/7] srcu: NMI-safe atomic SRCU readers, and their irqsave forms
Date: Wed, 11 Nov 2026 14:40:36 -0500	[thread overview]
Message-ID: <5edbc292-0004-43b7-9371-c3695afd9128@efficios.com> (raw)
In-Reply-To: <a8b4f18d81397124690a567b6a42da83ef2bc757.camel@infradead.org>

On 2026-11-11 14:37, David Woodhouse wrote:
> On Wed, 2026-11-11 at 14:33 -0500, Mathieu Desnoyers wrote:
>> On 2026-11-11 14:02, David Woodhouse wrote:
>>> The latter claim is only true in __srcu_read_lock_fast()/_fast_updown()
>>> isn't it? Not in the atomic-SRCU. Unless we do something like this on
>>> top?
>>
>> It is true for the atomic readers as well.  Without
>> CONFIG_NEED_SRCU_NMI_SAFE, include/linux/srcu.h defines
>> __srcu_read_lock_nmisafe() as an inline that calls __srcu_read_lock(),
>> and the same for unlock.  So x86 keeps this_cpu_inc() and smp_mb().
>> Your diff selects the same functions by hand.
>>
>> Only the architectures that select NEED_SRCU_NMI_SAFE get the atomic
>> increments.
> 
> You are lost in a twisty maze of helper functions, all alike...

I guess I had the best mentor in that regard! ;-)

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com

  reply	other threads:[~2026-11-11 19:40 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-11 14:59 Mathieu Desnoyers
2026-11-11 14:59 ` [PATCH v2 1/7] srcutiny: Do not call synchronize_rcu() from synchronize_srcu_atomic() Mathieu Desnoyers
2026-11-11 18:35   ` Paul E. McKenney
2026-11-11 14:59 ` [PATCH v2 2/7] srcu: Rule for using synchronize_srcu_atomic() from interrupt handlers Mathieu Desnoyers
2026-11-11 18:54   ` Paul E. McKenney
2026-11-11 14:59 ` [PATCH v2 3/7] srcu: Make atomic SRCU readers NMI-safe Mathieu Desnoyers
2026-11-11 19:55   ` Paul E. McKenney
2026-11-11 14:59 ` [PATCH v2 4/7] srcu: Add irqsave variants of the atomic SRCU readers Mathieu Desnoyers
2026-11-11 19:58   ` Paul E. McKenney
2026-11-11 20:04     ` Paul E. McKenney
2026-11-11 20:13       ` Mathieu Desnoyers
2026-11-11 14:59 ` [PATCH v2 5/7] rcutorture: Run NMI-safe SRCU readers from NMI Mathieu Desnoyers
2026-11-11 14:59 ` [PATCH v2 6/7] rcutorture: Test the irqsave forms of atomic SRCU readers Mathieu Desnoyers
2026-11-11 14:59 ` [PATCH v2 7/7] rcutorture: Check an atomic SRCU wait within an RCU reader Mathieu Desnoyers
2026-11-11 19:02 ` [PATCH v2 0/7] srcu: NMI-safe atomic SRCU readers, and their irqsave forms David Woodhouse
2026-11-11 19:33   ` Mathieu Desnoyers
2026-11-11 19:35     ` Paul E. McKenney
2026-11-11 19:37     ` David Woodhouse
2026-11-11 19:40       ` Mathieu Desnoyers [this message]
2026-11-11 19:50         ` Paul E. McKenney
2026-11-11 19:34   ` Paul E. McKenney

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