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=-5.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,URIBL_DBL_ABUSE_MALW,USER_AGENT_SANE_1 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 DA50EC2D0DB for ; Fri, 31 Jan 2020 17:49:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2E4B214D8 for ; Fri, 31 Jan 2020 17:49:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727183AbgAaRtk (ORCPT ); Fri, 31 Jan 2020 12:49:40 -0500 Received: from mx2.suse.de ([195.135.220.15]:43612 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726989AbgAaRtj (ORCPT ); Fri, 31 Jan 2020 12:49:39 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id DA393AF73; Fri, 31 Jan 2020 17:49:36 +0000 (UTC) Date: Fri, 31 Jan 2020 09:39:22 -0800 From: Davidlohr Bueso To: Alex Shi Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org, tglx@linutronix.de Subject: Re: [PATCH] locking/rtmutex: remove unused cmpxchg_relaxed Message-ID: <20200131173922.hjvugxuybrn2wbsn@linux-p48b> References: <1579595686-251535-1-git-send-email-alex.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <1579595686-251535-1-git-send-email-alex.shi@linux.alibaba.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Cc'ing tglx. On Tue, 21 Jan 2020, Alex Shi wrote: >No one use this macro after it was introduced. Better to remove it? You also need to remove it for the CONFIG_DEBUG_RT_MUTEXES=y case. > >Signed-off-by: Alex Shi >Cc: Peter Zijlstra >Cc: Davidlohr Bueso >Cc: Ingo Molnar >Cc: Will Deacon >Cc: linux-kernel@vger.kernel.org >--- > kernel/locking/rtmutex.c | 1 - > 1 file changed, 1 deletion(-) > >diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c >index 851bbb10819d..a849964a348d 100644 >--- a/kernel/locking/rtmutex.c >+++ b/kernel/locking/rtmutex.c >@@ -141,7 +141,6 @@ static void fixup_rt_mutex_waiters(struct rt_mutex *lock) > * set up. > */ > #ifndef CONFIG_DEBUG_RT_MUTEXES >-# define rt_mutex_cmpxchg_relaxed(l,c,n) (cmpxchg_relaxed(&l->owner, c, n) == c) > # define rt_mutex_cmpxchg_acquire(l,c,n) (cmpxchg_acquire(&l->owner, c, n) == c) > # define rt_mutex_cmpxchg_release(l,c,n) (cmpxchg_release(&l->owner, c, n) == c) Hmm unrelated, but do we want CCAS for rtmutex fastpath? Ie: (l->owner == c && cmpxchg_acquire(&l->owner, c, n) == c) That would optimize for the contended case and avoid the cmpxchg - it would also help if we ever do the top-waiter spin thing. Thanks, Davidlohr