From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEBDEC1975A for ; Wed, 25 Mar 2020 16:02:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9BAF20409 for ; Wed, 25 Mar 2020 16:02:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727980AbgCYQCs convert rfc822-to-8bit (ORCPT ); Wed, 25 Mar 2020 12:02:48 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:48461 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727768AbgCYQCs (ORCPT ); Wed, 25 Mar 2020 12:02:48 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1jH8Ts-0005AG-4C; Wed, 25 Mar 2020 17:02:12 +0100 Date: Wed, 25 Mar 2020 17:02:12 +0100 From: Sebastian Siewior To: Thomas Gleixner Cc: paulmck@kernel.org, LKML , Peter Zijlstra , Ingo Molnar , Linus Torvalds , Joel Fernandes , Oleg Nesterov , Davidlohr Bueso , Jonathan Corbet , Randy Dunlap , Logan Gunthorpe , Bjorn Helgaas , Kurt Schwemmer , linux-pci@vger.kernel.org, Greg Kroah-Hartman , Felipe Balbi , linux-usb@vger.kernel.org, Kalle Valo , "David S. Miller" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, Darren Hart , Andy Shevchenko , platform-driver-x86@vger.kernel.org, Zhang Rui , "Rafael J. Wysocki" , linux-pm@vger.kernel.org, Len Brown , linux-acpi@vger.kernel.org, kbuild test robot , Nick Hu , Greentime Hu , Vincent Chen , Guo Ren , linux-csky@vger.kernel.org, Brian Cain , linux-hexagon@vger.kernel.org, Tony Luck , Fenghua Yu , linux-ia64@vger.kernel.org, Michal Simek , Michael Ellerman , Arnd Bergmann , Geoff Levand , linuxppc-dev@lists.ozlabs.org, Davidlohr Bueso Subject: Re: Documentation/locking/locktypes: Further clarifications and wordsmithing Message-ID: <20200325160212.oavrni7gmzudnczv@linutronix.de> References: <20200323025501.GE3199@paulmck-ThinkPad-P72> <87r1xhz6qp.fsf@nanos.tec.linutronix.de> <20200325002811.GO19865@paulmck-ThinkPad-P72> <87wo78y5yy.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <87wo78y5yy.fsf@nanos.tec.linutronix.de> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 2020-03-25 13:27:49 [+0100], Thomas Gleixner wrote: > The documentation of rw_semaphores is wrong as it claims that the non-owner > reader release is not supported by RT. That's just history biased memory > distortion. > > Split the 'Owner semantics' section up and add separate sections for > semaphore and rw_semaphore to reflect reality. > > Aside of that the following updates are done: > > - Add pseudo code to document the spinlock state preserving mechanism on > PREEMPT_RT > > - Wordsmith the bitspinlock and lock nesting sections > > Co-developed-by: Paul McKenney > Signed-off-by: Paul McKenney > Signed-off-by: Thomas Gleixner Acked-by: Sebastian Andrzej Siewior > --- a/Documentation/locking/locktypes.rst > +++ b/Documentation/locking/locktypes.rst … > +rw_semaphore > +============ > + > +rw_semaphore is a multiple readers and single writer lock mechanism. > + > +On non-PREEMPT_RT kernels the implementation is fair, thus preventing > +writer starvation. > + > +rw_semaphore complies by default with the strict owner semantics, but there > +exist special-purpose interfaces that allow non-owner release for readers. > +These work independent of the kernel configuration. This reads funny, could be my English. "This works independent …" maybe? Sebastian