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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 5D4D8C4338F for ; Fri, 6 Aug 2021 11:01:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4095061181 for ; Fri, 6 Aug 2021 11:01:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245271AbhHFLB0 (ORCPT ); Fri, 6 Aug 2021 07:01:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245261AbhHFLBY (ORCPT ); Fri, 6 Aug 2021 07:01:24 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E216C061798 for ; Fri, 6 Aug 2021 04:01:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=REQ1W8sNJktjIPpaOp5ow7XK6buM4/6cGVuTXRlaEIU=; b=EPNGLjamYhabcCG2UgujoxkcIA 5C4CI6dfC2sfJg59jFnWBnQfwgrZdonWlawskbclRHtO11db150rO1qlLVxWPrKRjqoonQ9MPEuu7 CARlUqlfsLzXiFMtlIMXB3O51rvBz2Xwdm5nXVK1K/7vKfFypUJhjQ0v+TrRjC248sRH8AgXd27mn 1I4Mm8b3EIWNHfpLBb1KEFWJsBs2IS/X5dUXsK3Vp+YC7u/cV5bwq/mqMdso2+1XtqCUYsFmFH0jh 8z2aZNXrQ9/ZDtzHVIhybxx1gsUCPnUeF5jRY7T6FAGfGf1Y5lBuu2jIEn641Qa4Yfa2nz4Rfd24M 1K5wvI5w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBxau-006LPB-TX; Fri, 06 Aug 2021 11:00:53 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id E85A6980F93; Fri, 6 Aug 2021 13:00:51 +0200 (CEST) Date: Fri, 6 Aug 2021 13:00:51 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: LKML , Ingo Molnar , Juri Lelli , Steven Rostedt , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , Sebastian Andrzej Siewior , Davidlohr Bueso , Mike Galbraith Subject: Re: [patch V3 50/64] locking/rtmutex: Extend the rtmutex core to support ww_mutex Message-ID: <20210806110051.GF22037@worktop.programming.kicks-ass.net> References: <20210805151300.330412127@linutronix.de> <20210805153955.709189588@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210805153955.709189588@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 05, 2021 at 05:13:50PM +0200, Thomas Gleixner wrote: > static __always_inline bool __waiter_less(struct rb_node *a, const struct rb_node *b) > { > - return rt_mutex_waiter_less(__node_2_waiter(a), __node_2_waiter(b)); Given ^ > + struct rt_mutex_waiter *aw = __node_2_waiter(a); > + struct rt_mutex_waiter *bw = __node_2_waiter(b); > + > + if (rt_mutex_waiter_less(aw, bw)) > + return 1; We can, with this new build_ww_mutex(), do: if (!build_ww_mutex()) return 0; here, to preserve the old behaviour. > + if (rt_mutex_waiter_less(bw, aw)) > + return 0; > + > + /* NOTE: relies on waiter->ww_ctx being set before insertion */ > + if (build_ww_mutex() && aw->ww_ctx) { Then it can go away here. > + if (!bw->ww_ctx) > + return 1; > + > + return (signed long)(aw->ww_ctx->stamp - > + bw->ww_ctx->stamp) < 0; > + } > + > + return 0; > } Also, I found a note that said I had to check what this code does for !RT tasks, lemme go do that now.