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=-4.1 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 D8FC7C433E1 for ; Tue, 11 Aug 2020 15:43:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A88D520885 for ; Tue, 11 Aug 2020 15:43:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="xC/kPOyF"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="N2bSrMLX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729184AbgHKPnT (ORCPT ); Tue, 11 Aug 2020 11:43:19 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:59704 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728986AbgHKPnS (ORCPT ); Tue, 11 Aug 2020 11:43:18 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1597160596; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2Y8wKgLFG/BB38s4C+mIP9XqAuHjOkKcj6UCnkVK68w=; b=xC/kPOyFICzX+/DqLxf4qDnyIsUn+RJHbjTmGdh/IuE9OjfBlhAtRmfzWbaaaDKglABKOI AaVz3AvajZJntEW5ZWAuXZDAjD+5FcyJMMZ6PtpbEft3HBxWSzuAZkBQFRjXkQN83hsBtt 7Q1baAzcdYNTNy4RQfcqMVrFkG3mvDxGTFDVndVN7be3k5iro0yMG7ITtQa+Xf3Ot/CnAE u+UhZJOBDz0BjuIXLFF0yAbS9ipObwVLyzRs46I7pSqVyZgHFDzGytbEXEI6vrygbLNcTT 8PoMSowNYURNmwoBAIK8jXaGypiCTuZIeQ7BQqdbvYoE/dVrySU26GePTD/Bwg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1597160596; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2Y8wKgLFG/BB38s4C+mIP9XqAuHjOkKcj6UCnkVK68w=; b=N2bSrMLXJ9rTsShDyvIvw4dO2c6WDCQdjtjkKblf8yaYb74SCiqksA5/vA3fBGMpBC8bwh KlDoMDpvC5/Y05DA== To: paulmck@kernel.org Cc: Michal Hocko , 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 In-Reply-To: <20200811153327.GW4295@paulmck-ThinkPad-P72> References: <20200809204354.20137-1-urezki@gmail.com> <20200809204354.20137-2-urezki@gmail.com> <20200810123141.GF4773@dhcp22.suse.cz> <20200810160739.GA29884@pc636> <20200810192525.GG4773@dhcp22.suse.cz> <87pn7x6y4a.fsf@nanos.tec.linutronix.de> <20200811153327.GW4295@paulmck-ThinkPad-P72> Date: Tue, 11 Aug 2020 17:43:16 +0200 Message-ID: <87h7t96ve3.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org "Paul E. McKenney" writes: > On Tue, Aug 11, 2020 at 04:44:21PM +0200, Thomas Gleixner wrote: >> Now RCU creates a new thing which enforces to make page allocation in >> atomic context possible on RT. What for? >> >> What's the actual use case in truly atomic context for this new thing on >> an RT kernel? > > It is not just RT kernels. CONFIG_PROVE_RAW_LOCK_NESTING=y propagates > this constraint to all configurations, and a patch in your new favorite > subsystem really did trigger this lockdep check in a non-RT kernel. > >> The actual RCU code disabling interrupts is an implementation detail >> which can easily be mitigated with a local lock. > > In this case, we are in raw-spinlock context on entry to kfree_rcu(). Where?