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[23.128.96.18]) by mx.google.com with ESMTP id m7si20030728edd.486.2021.04.07.14.28.51; Wed, 07 Apr 2021 14:29:15 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=hT6rnPyg; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234192AbhDGPze (ORCPT + 99 others); Wed, 7 Apr 2021 11:55:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232716AbhDGPze (ORCPT ); Wed, 7 Apr 2021 11:55:34 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61E3FC061756; Wed, 7 Apr 2021 08:55:24 -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-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=a8elwdZOsCHEPMraxac9e3Y9q00OjQSrAqqfC563Li0=; b=hT6rnPygmAOYuDBJ32gkAH24DN y0EskBQYVhmESQygX/JL1U9CFVN+vrw/X7f9JTPcPCgdQ0LfUq9HawJDre8t8SVigUPAP7gB/glVm qgAIylcHxk4Si+FR+ujhExsOgHLe7mhsLbe5p7LaCwVlflxb5He+EL7JVv1UnjRMWP6inKBD5KMwv nu0686GQIB6TMS465yR1qCNjO7osE7Oz1r2O1wVhf1N2AdhYQEaUzwHGexje1/o1iKA3DErFp/mQM fUWkDL41gAFBEkN8r5Uj8W9Nj8cxy31EKCUCk8SAm9oHb9jRFGbmZMBzzEb00QQllAZzoElXkIyXB 1r8acCwQ==; 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 1lUASU-00Ehp1-Ej; Wed, 07 Apr 2021 15:51:45 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 994483015D3; Wed, 7 Apr 2021 17:51:07 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 42E382BF09268; Wed, 7 Apr 2021 17:51:07 +0200 (CEST) Date: Wed, 7 Apr 2021 17:51:07 +0200 From: Peter Zijlstra To: Christoph =?iso-8859-1?Q?M=FCllner?= Cc: Christoph Hellwig , Guo Ren , linux-riscv , Linux Kernel Mailing List , linux-csky@vger.kernel.org, linux-arch , Guo Ren , Will Deacon , Ingo Molnar , Waiman Long , Arnd Bergmann , Anup Patel Subject: Re: [PATCH v4 3/4] locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32 Message-ID: References: <1616868399-82848-4-git-send-email-guoren@kernel.org> <20210407094224.GA3393992@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 07, 2021 at 04:29:12PM +0200, Christoph M?llner wrote: > Further, it is not the case that RISC-V has no guarantees at all. > It just does not provide a forward progress guarantee for a > synchronization implementation, > that writes in an endless loop to a memory location while trying to > complete an LL/SC > loop on the same memory location at the same time. Userspace can DoS the kernel that way, see futex.