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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C225CC54EBC for ; Thu, 12 Jan 2023 13:18:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231443AbjALNST (ORCPT ); Thu, 12 Jan 2023 08:18:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232989AbjALNSQ (ORCPT ); Thu, 12 Jan 2023 08:18:16 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 172751E3F5; Thu, 12 Jan 2023 05:18:14 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B908EB81DC4; Thu, 12 Jan 2023 13:18:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAD57C433EF; Thu, 12 Jan 2023 13:18:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673529491; bh=BDvN5ZLk/njQe+svUcrjrAn0YUpLJT8kpaTkXNuJp98=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XSaxD7QkgYx9p5tWhyMFfpdO2b+EEtrBZAjChsbD7SrzlCNF53BprbbzhkfsRlW9c d5Deemm2bVOryepkiiJ351o4ZEzO5XUKgzoKk5rIyxpzdmtIyDwfiNKmiyjKOgl6h4 OXKdhLB7ZpexCU6YB1Q7Y+003QUdnLYcThMbVPJZuXptMKSjpqEhrxj1JtQ0eqBmZ5 IatZN8yfga/80omt4IMZPC0PVuA8EgSt+0aOXpy2f/avMyr+kvkM+e8+jnyrBVMPca BDuWeh7IeuSAse6JL+O60gf6iZvGqYN2CVX2CWdtBc+rBMV117lng958X1WsdfN5lh YFKshjYRU4RXA== Date: Thu, 12 Jan 2023 14:18:08 +0100 From: Frederic Weisbecker To: Zqiang Cc: paulmck@kernel.org, quic_neeraju@quicinc.com, joel@joelfernandes.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] rcu: Fix the start_poll_synchronize_rcu_expedited() be invoked very early Message-ID: References: <20230112075629.1661429-1-qiang1.zhang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230112075629.1661429-1-qiang1.zhang@intel.com> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Thu, Jan 12, 2023 at 03:56:29PM +0800, Zqiang wrote: > Currently, the start_poll_synchronize_rcu_expedited() can be invoked > very early. before rcu_init(), the rcu_data structure's->mynode is not > initialized, if invoke start_poll_synchronize_rcu_expedited() before > rcu_init(), will trigger a null rcu_node structure's->exp_seq_poll access. > > This commit add boot_exp_seq_poll_rq member to rcu_state structure to > store seq number return by invoke start_poll_synchronize_rcu_expedited() > very early. > > Fixes: d96c52fe4907 ("rcu: Add polled expedited grace-period primitives") > Signed-off-by: Zqiang Reviewed-by: Frederic Weisbecker Just a nit below: > --- > kernel/rcu/tree.c | 3 ++- > kernel/rcu/tree.h | 1 + > kernel/rcu/tree_exp.h | 6 ++++-- > 3 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 63545d79da51..12f0891ce7f4 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -92,6 +92,7 @@ static struct rcu_state rcu_state = { > .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), > .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), > .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, > + .boot_exp_seq_poll_rq = RCU_GET_STATE_COMPLETED, > }; > > /* Dump rcu_node combining tree at boot to verify correct setup. */ > @@ -4938,7 +4939,7 @@ void __init rcu_init(void) > qovld_calc = qovld; > > // Kick-start any polled grace periods that started early. > - if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1)) > + if (!(rcu_state.boot_exp_seq_poll_rq & 0x1)) This can be "if (!(rcu_state.boot_exp_seq_poll_rq == RCU_GET_STATE_COMPLETED))" > (void)start_poll_synchronize_rcu_expedited(); > > rcu_test_sync_prims(); > diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h > index 192536916f9a..ae50ca6853ad 100644 > --- a/kernel/rcu/tree.h > +++ b/kernel/rcu/tree.h > @@ -397,6 +397,7 @@ struct rcu_state { > /* Synchronize offline with */ > /* GP pre-initialization. */ > int nocb_is_setup; /* nocb is setup from boot */ > + unsigned long boot_exp_seq_poll_rq; A comment on the right can mention: "/* exp seq poll request before rcu_init() */" Thanks! > }; > > /* Values for rcu_state structure's gp_flags field. */ > diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h > index 956cd459ba7f..1b35a1e233d9 100644 > --- a/kernel/rcu/tree_exp.h > +++ b/kernel/rcu/tree_exp.h > @@ -1068,9 +1068,11 @@ unsigned long start_poll_synchronize_rcu_expedited(void) > if (rcu_init_invoked()) > raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags); > if (!poll_state_synchronize_rcu(s)) { > - rnp->exp_seq_poll_rq = s; > - if (rcu_init_invoked()) > + if (rcu_init_invoked()) { > + rnp->exp_seq_poll_rq = s; > queue_work(rcu_gp_wq, &rnp->exp_poll_wq); > + } else > + rcu_state.boot_exp_seq_poll_rq = s; > } > if (rcu_init_invoked()) > raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags); > -- > 2.25.1 >