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=-5.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 42398C31E40 for ; Tue, 13 Aug 2019 01:05:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1137F20665 for ; Tue, 13 Aug 2019 01:05:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="Mv241Fhb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726479AbfHMBF2 (ORCPT ); Mon, 12 Aug 2019 21:05:28 -0400 Received: from mail-pg1-f172.google.com ([209.85.215.172]:45014 "EHLO mail-pg1-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726296AbfHMBF2 (ORCPT ); Mon, 12 Aug 2019 21:05:28 -0400 Received: by mail-pg1-f172.google.com with SMTP id i18so50352362pgl.11 for ; Mon, 12 Aug 2019 18:05:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=qKDtRrj8VSA0AxTKmeWFFvgiD7uTonCobI1vWS2Oa24=; b=Mv241FhbNqODnmgbBHKpokjGwoA0ZA2DLfDRJnJGl1/Fo4TiGuXXkE7hQG0C4OsZb3 42o8l9VPl1/SSH47hrtWpR4TsJxQaR0adyBnkQCxIY7QHqU4QjaZNrAyB4BcE2RfYQX3 cUMTJ1gggVu8mQrZYUNL9wvtewVVIjYMrhfYQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=qKDtRrj8VSA0AxTKmeWFFvgiD7uTonCobI1vWS2Oa24=; b=drO+9fM5byAe9disq16CosEg37RIQr7maN1BGB05iAgJqub1gOG68d6951LrbFKYMi p34Jz3nx4XgJ/yfRoaBWqaaiE4RZMJehjSLlm2xxfBcQjmi8ffHbFwYNPxLV+1nnPGqP AowD/ZlyynmOF5mJqYsJZAV8ay3BauPV+rX4szHdjS/vLc86qZATshtuX1+t5G2BZC4K Eu+FWQKd60ohpA2zIOW8ObmFfPnj/hW0IdS3so8aoBlxxpiI1N+Wk9AkNsPEdpTndx6t zDQg+OfPRJll6y5zjtYFZU91SgmbFT2zJNv/oNtWcvs/6ccH6xWpCtxbUVYBaUFZUy/M VJhg== X-Gm-Message-State: APjAAAUTdJvXeAGSTPq4YLyv7rEqSPH4TA4wlCLueQ98i9erdpBq4c0P mhZIhcGe5LN1wlJvconY6t45+2hdYMg= X-Google-Smtp-Source: APXvYqy+4vu3quu56fOnYCKxkR9ImMB7DR2raLLo9n4l3tA6ML/FY2VBqoKnDxqvoSlB5D3o5MYGJw== X-Received: by 2002:a65:430b:: with SMTP id j11mr32045818pgq.383.1565658327681; Mon, 12 Aug 2019 18:05:27 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id 67sm817885pjo.29.2019.08.12.18.05.26 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 12 Aug 2019 18:05:26 -0700 (PDT) Date: Mon, 12 Aug 2019 21:05:25 -0400 From: Joel Fernandes To: "Paul E. McKenney" Cc: rcu@vger.kernel.org Subject: Re: need_heavy_qs flag for PREEMPT=y kernels Message-ID: <20190813010525.GB129011@google.com> References: <20190811180852.GA128944@google.com> <20190811211318.GX28441@linux.ibm.com> <20190812032142.GA171001@google.com> <20190812035306.GE28441@linux.ibm.com> <20190812212013.GB48751@google.com> <20190812230138.GS28441@linux.ibm.com> <20190813010249.GA129011@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190813010249.GA129011@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Mon, Aug 12, 2019 at 09:02:49PM -0400, Joel Fernandes wrote: [snip] > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 8c494a692728..ad906d6a74fb 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -651,6 +651,12 @@ static __always_inline void rcu_nmi_exit_common(bool irq) > > */ > > if (rdp->dynticks_nmi_nesting != 1) { > > trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks); > > + if (tick_nohz_full_cpu(rdp->cpu) && > > + rdp->dynticks_nmi_nesting == 2 && > > + rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { > > + rdp->rcu_forced_tick = true; > > + tick_dep_set_cpu(rdp->cpu, TICK_DEP_MASK_RCU); > > + } > > > Instead of checking dynticks_nmi_nesting == 2 in rcu_nmi_exit_common(), can > we do the tick_dep_set_cpu(rdp->cpu, TICK_DEP_MASK_RCU) from > rcu_nmi_enter_common() ? We could add this code there, under the "if > (rcu_dynticks_curr_cpu_in_eqs())". Actually, the other way. if (!rcu_dynticks_curr_cpu_in_eqs()) then do the tick_dep_set_cpu(). thanks, - Joel