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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 C5A54C433DF for ; Thu, 13 Aug 2020 18:31:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A67E22078B for ; Thu, 13 Aug 2020 18:31:37 +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="OABqsCGb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726567AbgHMSbh (ORCPT ); Thu, 13 Aug 2020 14:31:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726167AbgHMSbg (ORCPT ); Thu, 13 Aug 2020 14:31:36 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C7E6C061757; Thu, 13 Aug 2020 11:31:36 -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=SH9o16/Qf0/iPL9rM1LGxVVZdzQj3ynCJRzANMbMLh8=; b=OABqsCGbsESN3jXxQUyFvsjtkH Trbqm8qEElLJ+OBn/xH1496gay5z4y2bWGu+yakc/VBmK6oj1HYPkZEID8voaWSpzi5WstQDz9Ad9 mcEeXP+y4WcGjuPCYmG7caPiU0Qhp3KMixtAtoLsYaEax+P/iPVYKrrHAfBjNGeMjRh0HRUfsfOOY E+rUEqRQQ2LcwdmvSiUdQ+LcaHY8TTrjkH5wFJJ3/oU/s1/PGZK2+51nfIi1W3zHQDzXIXASm4Qc7 3DvNaqO++o1tXrkKZffjdR//a+dY2E2odqWzH0ZLqnb9tfuwo/KITb0YEnfUTQhxhu7MyJYUWM3GD xssnZqGw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k6I0Z-00020f-Fv; Thu, 13 Aug 2020 18:31:23 +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 C7E2B304D58; Thu, 13 Aug 2020 20:31:21 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B5A0A2B929A4A; Thu, 13 Aug 2020 20:31:21 +0200 (CEST) Date: Thu, 13 Aug 2020 20:31:21 +0200 From: peterz@infradead.org To: "Paul E. McKenney" Cc: Michal Hocko , Thomas Gleixner , Uladzislau Rezki , LKML , RCU , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Matthew Wilcox , "Theodore Y . Ts'o" , Joel Fernandes , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag Message-ID: <20200813183121.GY2674@hirez.programming.kicks-ass.net> References: <20200813095840.GA25268@pc636> <874kp6llzb.fsf@nanos.tec.linutronix.de> <20200813133308.GK9477@dhcp22.suse.cz> <87sgcqty0e.fsf@nanos.tec.linutronix.de> <20200813145335.GN9477@dhcp22.suse.cz> <20200813154159.GR4295@paulmck-ThinkPad-P72> <20200813155412.GP9477@dhcp22.suse.cz> <20200813160442.GV4295@paulmck-ThinkPad-P72> <20200813161357.GQ9477@dhcp22.suse.cz> <20200813162904.GX4295@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200813162904.GX4295@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Thu, Aug 13, 2020 at 09:29:04AM -0700, Paul E. McKenney wrote: > OK. So the current situation requires a choice between these these > alternatives, each of which has shortcomings that have been mentioned > earlier in this thread: > > 1. Prohibit invoking allocators from raw atomic context, such > as when holding a raw spinlock. This! This has always been the case, why are we even considering change here? > 2. Adding a GFP_ flag. The patch 1/2 in this thread is horrendous crap. > 3. Reusing existing GFP_ flags/values/whatever to communicate > the raw-context information that was to be communicated by > the new GFP_ flag. > > 4. Making lockdep forgive acquiring spinlocks while holding > raw spinlocks, but only in CONFIG_PREEMPT_NONE=y kernels. > > Am I missing anything? How would 4 solve anything? In other words, what is the actual friggin problem? I've not seen one described anywhere.