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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 03C30C4724C for ; Mon, 4 May 2020 17:08:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D19C5206A5 for ; Mon, 4 May 2020 17:08:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588612123; bh=ypOPsyYM0K55BJG1G3egFRLHvuXBDVqQU1VVRfu/SmI=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=zKvn+1sbjT1Nkt/4MbAKQmNYQfaXPMA6sWHSGahxpeZnlgmcvIgFrqR4GHIhaiYTk 6t86dAwBG/YsL55gNLSARR9xY9CTlxPP2rmckT7yrj1KlZCtz9F74E9lV/wKr3MLw8 L3mHf09HfxY5UOKytjGcf7thcWJqaSKIRVvbBLuU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730039AbgEDRIg (ORCPT ); Mon, 4 May 2020 13:08:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:41996 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730050AbgEDRId (ORCPT ); Mon, 4 May 2020 13:08:33 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5E098206A5; Mon, 4 May 2020 17:08:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588612113; bh=ypOPsyYM0K55BJG1G3egFRLHvuXBDVqQU1VVRfu/SmI=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=RKfXMVsYI9cCeE5MKGX2AOl3oY35VW2WB/58+/IOr+d/JQXue/IaiKgqmCgOJGm4B i+jF5WKXBlxuVVX6hEYowk7XZ289PQhVgg+ULfZQmrw2XXU2ASjIWgXOdSP+cQ/3F9 SVOSM/N5viQjLNYhnu2DJrfCMGi/kotafxgWEzDQ= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 3AA7835226F4; Mon, 4 May 2020 10:08:33 -0700 (PDT) Date: Mon, 4 May 2020 10:08:33 -0700 From: "Paul E. McKenney" To: Uladzislau Rezki Cc: Joel Fernandes , LKML , linux-mm@kvack.org, Andrew Morton , "Theodore Y . Ts'o" , Matthew Wilcox , RCU , Oleksiy Avramchenko Subject: Re: [PATCH 19/24] rcu/tree: Support reclaim for head-less object Message-ID: <20200504170833.GQ2869@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200428205903.61704-1-urezki@gmail.com> <20200428205903.61704-20-urezki@gmail.com> <20200501223909.GF7560@paulmck-ThinkPad-P72> <20200504001258.GD197097@google.com> <20200504002855.GF2869@paulmck-ThinkPad-P72> <20200504003237.GD212435@google.com> <20200504142153.GG17577@pc636> <20200504153147.GL2869@paulmck-ThinkPad-P72> <20200504165629.GA20257@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200504165629.GA20257@pc636> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Mon, May 04, 2020 at 06:56:29PM +0200, Uladzislau Rezki wrote: > > > > > > For single argument we can drop the lock before the entry to the page > > > allocator. Because it follows might_sleep() anotation we avoid of having > > > a situation when spinlock(rt mutex) is taken from any atomic context. > > > > > > Since the lock is dropped the current context can be interrupted by > > > an IRQ which in its turn can also call kvfree_rcu() on current CPU. > > > In that case it must be double argument(single is not allowed) kvfree_rcu() > > > call. For PREEMPT_RT if no cache everything is reverted to rcu_head usage, > > > i.e. the entry to page allocator is bypassed. > > > > > > It can be addressed as a separate patch and send out later on if we > > > are on the same page. > > > > > > Paul, Joel what are your opinions? > > > > I strongly prefer that it be removed from the series. I do understand > > that this is a bit more hassle right now, but this does help avoid > > confusion in the future, plus perhaps also avoiding issues with future > > bisections. > > > We have already decided to get rid of it, i mean small allocations(dynamic > rcu_head attaching). I will exclude it from next patch-set version. Very good, and thank you!!! Thanx, Paul