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 3917BC46467 for ; Wed, 11 Jan 2023 14:49:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232676AbjAKOtJ (ORCPT ); Wed, 11 Jan 2023 09:49:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234188AbjAKOtC (ORCPT ); Wed, 11 Jan 2023 09:49:02 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3433411C2C; Wed, 11 Jan 2023 06:48:49 -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 D975FB81C0A; Wed, 11 Jan 2023 14:48:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06D82C433D2; Wed, 11 Jan 2023 14:48:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673448526; bh=UEfl0KhVxYyXipkkr67e2P9gmRximnKB5GfIk2W8EsI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dzzVw6+qEMqRcc74jyTIdwny/0zFquyCQRecNUHhIgC4TAhKlfPSzjOmLFOJYxx6Y dby7NZLeH7KuotpImqA062vIQbVEaE6P1yIyonxoVPGOth5lHX/kM5QDVyM2E7wnfC eTkgxEM4YwCFbRFV3KhvPMj0iWWu9LVNGNRldO+qwQO3PLiQUe1FqxSb2iQIRSOAc7 ZMZeLrjCDIWOoYiWB12E+2L9sNb2vSclVnXd7WlVyPlqaMqToS7mNsn/Wsywz4QWLg PqDgwzBWtRnT9GsgY+VCgVBA2ftABOEBnypUjjuJHWdKCjCTSQ7MIFBipCWZXe+K5N OZmbpZ+r6QVgA== Date: Wed, 11 Jan 2023 15:48:43 +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] rcu: Fix the start_poll_synchronize_rcu_expedited() be invoked very early Message-ID: References: <20230111131453.1626214-1-qiang1.zhang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230111131453.1626214-1-qiang1.zhang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 11, 2023 at 09:14:53PM +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 access to NULL mynode pointer. > > This commit therefore add exp_seq_poll_rq member to rcu_state structure > to store snap seq number Is it even sane to poll that early in the morning? :-) > > Signed-off-by: Zqiang > --- > 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..34b13d6bd8c4 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, > + .exp_seq_poll_rq = RCU_GET_STATE_COMPLETED, I don't know if we really want to fix this, but assuming we do, can we rename it to boot_exp_seq_poll_rq? To avoid later confusion. Thanks.