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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 9A27BC282CE for ; Tue, 4 Jun 2019 16:54:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E56623CB9 for ; Tue, 4 Jun 2019 16:54:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728021AbfFDQys (ORCPT ); Tue, 4 Jun 2019 12:54:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50786 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727838AbfFDQys (ORCPT ); Tue, 4 Jun 2019 12:54:48 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F354E30C1AEA; Tue, 4 Jun 2019 16:54:42 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-85.bos.redhat.com [10.18.17.85]) by smtp.corp.redhat.com (Postfix) with ESMTP id AA18360566; Tue, 4 Jun 2019 16:54:39 +0000 (UTC) Subject: Re: [PATCH v8 14/19] locking/rwsem: Enable time-based spinning on reader-owned rwsem To: Peter Zijlstra Cc: Ingo Molnar , Will Deacon , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org, Davidlohr Bueso , Linus Torvalds , Tim Chen , huang ying References: <20190520205918.22251-1-longman@redhat.com> <20190520205918.22251-15-longman@redhat.com> <20190604090309.GG3402@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: Date: Tue, 4 Jun 2019 12:54:39 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190604090309.GG3402@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Tue, 04 Jun 2019 16:54:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/4/19 5:03 AM, Peter Zijlstra wrote: > On Mon, May 20, 2019 at 04:59:13PM -0400, Waiman Long wrote: >> +static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem) >> +{ >> + long owner = atomic_long_read(&sem->owner); >> + >> + while (owner & RWSEM_READER_OWNED) { >> + if (owner & RWSEM_NONSPINNABLE) >> + break; >> + owner = atomic_long_cmpxchg(&sem->owner, owner, >> + owner | RWSEM_NONSPINNABLE); >> + } >> +} > --- a/kernel/locking/rwsem.c > +++ b/kernel/locking/rwsem.c > @@ -206,12 +206,13 @@ static inline void rwsem_set_nonspinnabl > { > long owner = atomic_long_read(&sem->owner); > > - while (owner & RWSEM_READER_OWNED) { > + do { > + if (!(owner & RWSEM_READER_OWNED)) > + break; > if (owner & RWSEM_NONSPINNABLE) > break; > - owner = atomic_long_cmpxchg(&sem->owner, owner, > - owner | RWSEM_NONSPINNABLE); > - } > + } while (!atomic_long_try_cmpxchg(&sem->owner, &owner, > + owner | RWSEM_NONSPINNABLE)); > } > > /* Sure. Thanks, Longman