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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 3C883C43603 for ; Wed, 18 Dec 2019 20:39:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 01CE0206A5 for ; Wed, 18 Dec 2019 20:39:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="XSIt63bn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727282AbfLRUjx (ORCPT ); Wed, 18 Dec 2019 15:39:53 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:47466 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726387AbfLRUjw (ORCPT ); Wed, 18 Dec 2019 15:39:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=5IRekf7Hfq0F+Zs5ey5GQlKOYNtd0pnVixx2++Tjts0=; b=XSIt63bn3+h51oZ/5uaig/NOu tFArHm61DH2FN0mgqglrTl5zKVhpSO7LuMmNRCoIXRmTZt5bZoRkL5YY9B9nkcVaeD5/dD9z+X00p tN0VRF1fIvb7Rp0xMS5MDbXsddPNA0eLVfg9XM+jBSFMm/XIXuaAyAGNZphBQlWjc7j2fzzbhWMEt k+RcqOpGsZtcOCG0OeJqGrYr8VtZ3pduTlmbJiTo1Wa0bTET8aziDg+/qRkipWT4/Fff//AH1Mdym 1Vbaxyye5BoJhHTrsGLym2XeSxr0lP9xMRW/VzMveg8bL2NTgzitT6LtVzLATjjErAcV7hXPkFLfR GbdToNU0A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1ihg6m-0002vS-Tm; Wed, 18 Dec 2019 20:39:49 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id E8D47980E35; Wed, 18 Dec 2019 21:39:46 +0100 (CET) Date: Wed, 18 Dec 2019 21:39:46 +0100 From: Peter Zijlstra To: Davidlohr Bueso Cc: David Howells , linux-afs@lists.infradead.org, Ingo Molnar , Will Deacon , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH] rxrpc: struct mutex cannot be used for rxrpc_call::user_mutex Message-ID: <20191218203946.GL11457@worktop.programming.kicks-ass.net> References: <157659672074.19580.11641288666811539040.stgit@warthog.procyon.org.uk> <20191218135047.GS2844@hirez.programming.kicks-ass.net> <20191218190833.ufpxjrvin5jvp3m5@linux-p48b> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191218190833.ufpxjrvin5jvp3m5@linux-p48b> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 18, 2019 at 11:08:33AM -0800, Davidlohr Bueso wrote: > On Wed, 18 Dec 2019, Peter Zijlstra wrote: > > > On Tue, Dec 17, 2019 at 03:32:00PM +0000, David Howells wrote: > > > Standard kernel mutexes cannot be used in any way from interrupt or softirq > > > context, so the user_mutex which manages access to a call cannot be a mutex > > > since on a new call the mutex must start off locked and be unlocked within > > > the softirq handler to prevent userspace interfering with a call we're > > > setting up. > > > > > > Commit a0855d24fc22d49cdc25664fb224caee16998683 ("locking/mutex: Complain > > > upon mutex API misuse in IRQ contexts") causes big warnings to be splashed > > > in dmesg for each a new call that comes in from the server. > > > > FYI that patch has currently been reverted. > > > > commit c571b72e2b845ca0519670cb7c4b5fe5f56498a5 (tip/locking/urgent, tip/locking-urgent-for-linus) > > Will we ever want to re-add this warning (along with writer rwsems) at some point? Yes, we can try again for the next cycle.