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From: Boqun Feng <boqun.feng@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Mike Galbraith <efault@gmx.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] locking: rwbase: Take care of ordering guarantee for fastpath reader
Date: Sat, 4 Sep 2021 18:19:27 +0800	[thread overview]
Message-ID: <YTNIL81163O/3gea@boqun-archlinux> (raw)
In-Reply-To: <20210904101429.GB4323@worktop.programming.kicks-ass.net>

On Sat, Sep 04, 2021 at 12:14:29PM +0200, Peter Zijlstra wrote:
> On Fri, Sep 03, 2021 at 10:50:58PM +0800, Boqun Feng wrote:
> > > 	 * ordering, either is strong enough to provide ACQUIRE order
> > > 	 * for the above load of @readers.
> > > 	 */
> > > 	rwbase_set_and_save_current_state(state);
> > > 	raw_spin_lock_irqsave(&rtm->wait_lock, flags);
> > > 
> > > 	while (readers) {
> > > 		...
> > > 		readers = atomic_read(&rwb->readers);
> > 
> > The above should be _acquire(), right? Pairs with the last reader
> > exiting the critical section and dec ->readers to 0. If so, it
> > undermines the necessity of the restructure?
> 
> This is the one that's followed by set_current_state(), no?

You're right. I was missing that ;-/

Regards,
Boqun

> 

  reply	other threads:[~2021-09-04 10:20 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-01 15:06 Boqun Feng
2021-09-01 18:53 ` Waiman Long
2021-09-01 20:22 ` Davidlohr Bueso
2021-09-02  5:02   ` Boqun Feng
2021-09-02 11:55 ` Peter Zijlstra
2021-09-03 14:50   ` Boqun Feng
2021-09-04 10:12     ` Peter Zijlstra
2021-09-04 10:14     ` Peter Zijlstra
2021-09-04 10:19       ` Boqun Feng [this message]
2021-09-08 11:51 ` Peter Zijlstra
2021-09-08 12:14   ` Peter Zijlstra
2021-09-08 13:00     ` Boqun Feng
2021-09-08 13:08   ` Boqun Feng
2021-09-08 14:41     ` Peter Zijlstra
2021-09-08 14:49       ` Peter Zijlstra
2021-09-08 18:34         ` Davidlohr Bueso
2021-09-08 13:27   ` Boqun Feng

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