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 3CDB4C433E0 for ; Mon, 29 Mar 2021 11:32:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 099116193A for ; Mon, 29 Mar 2021 11:32:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230466AbhC2Lby (ORCPT ); Mon, 29 Mar 2021 07:31:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231154AbhC2Lba (ORCPT ); Mon, 29 Mar 2021 07:31:30 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE170C061574; Mon, 29 Mar 2021 04:31:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=xAASgCT1znE4iZyX4yKtFW+FR4NtFv4F0rZP0TttRpc=; b=IUiKLtt370+VXpr4Dpb9tIRnmD lUlt8V0bVGbfLA+R8YSPIs2KN/WpHeEsLTx1xJLbLiXLynAZmIxYNh4kuFIPd1cjaXGTgOSWQoOIV QETpqcvhbwpVKGfbKrnWvzkGFspWw6FRMud3euBEeDrqOAmp45mWd2u7Kvf3O9M4aI5VFhAcu8//F AOGsqL6Ut9BtLNCe6g8wHoyGxVKxBkiRTrveBGZbdnHRjwFwVYBvF/DfhKrlZ9HZXRFFvwsnKDWWN e5CnjI2RJ1h+QIvFIOvGX8kRLrM3d7ZO9E4RhkJ9yNOU24aaT28io+SH1vNMaNB0s+x2RrCPd/ZBl 5izOhRpA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lQq5j-001TUs-4F; Mon, 29 Mar 2021 11:30:08 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 982223069B1; Mon, 29 Mar 2021 13:29:54 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 85F90207539C8; Mon, 29 Mar 2021 13:29:54 +0200 (CEST) Date: Mon, 29 Mar 2021 13:29:54 +0200 From: Peter Zijlstra To: Arnd Bergmann Cc: Guo Ren , linux-riscv , Linux Kernel Mailing List , linux-csky@vger.kernel.org, linux-arch , Guo Ren , Will Deacon , Ingo Molnar , Waiman Long , Anup Patel , Sebastian Andrzej Siewior Subject: Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32 Message-ID: References: <1616868399-82848-1-git-send-email-guoren@kernel.org> <1616868399-82848-4-git-send-email-guoren@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-csky@vger.kernel.org On Mon, Mar 29, 2021 at 01:16:53PM +0200, Peter Zijlstra wrote: > Anyway, an additional 'funny' is that I suspect you cannot prove fwd > progress of the entire primitive with any of this on. But who cares > about details anyway.. :/ What's the architectural guarantee on LL/SC progress for RISC-V ? And what if you double loop it like cmpxchg() ?