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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 25530C47254 for ; Fri, 1 May 2020 21:17:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4ABC2166E for ; Fri, 1 May 2020 21:17:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588367825; bh=gcWqVApgJs+BB978Fby692FvXoFwUlGeY+pFd8nhOMY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=TKCj5YWs6sEOIyMbP8ZiJ2Pe4Bs7mBAdcUXLP014QmC9AvLrxSukGMgSFMLt5FX6g FMvrfdpge7JvGfI4vvo2pHbjpjn4K0+fpFTyx2dcWJbMFPqrnm8GhvjLMnfghTzPV8 YzmpdofEcFiUL40WWb2ICZK3u9R52vIwbpe1Xa/g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726463AbgEAVRF (ORCPT ); Fri, 1 May 2020 17:17:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:38708 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726045AbgEAVRE (ORCPT ); Fri, 1 May 2020 17:17:04 -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 CF8A22073E; Fri, 1 May 2020 21:17:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588367823; bh=gcWqVApgJs+BB978Fby692FvXoFwUlGeY+pFd8nhOMY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=bH738pactjRZOPIK/6+Eo1lOB7GMdmeQ8itFo5KMUOx6C55Y4n5/hvcRJRpZEhOcy oKilnMUoRczmYFwKycghRDoRcQ6yI/ww+82eqziDVZunSRhtiOLvtld0N/34+o9YHA l0CK/CfLUvzXsZwSMYH+jOpcKiTG6d74tOAX8VlA= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 94DA63522B72; Fri, 1 May 2020 14:17:03 -0700 (PDT) Date: Fri, 1 May 2020 14:17:03 -0700 From: "Paul E. McKenney" To: "Uladzislau Rezki (Sony)" Cc: LKML , linux-mm@kvack.org, Andrew Morton , "Theodore Y . Ts'o" , Matthew Wilcox , Joel Fernandes , RCU , Oleksiy Avramchenko , Sebastian Andrzej Siewior Subject: Re: [PATCH 08/24] rcu/tree: Use static initializer for krc.lock Message-ID: <20200501211703.GC7560@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200428205903.61704-1-urezki@gmail.com> <20200428205903.61704-9-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200428205903.61704-9-urezki@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 28, 2020 at 10:58:47PM +0200, Uladzislau Rezki (Sony) wrote: > From: Sebastian Andrzej Siewior > > The per-CPU variable is initialized at runtime in > kfree_rcu_batch_init(). This function is invoked before > 'rcu_scheduler_active' is set to 'RCU_SCHEDULER_RUNNING'. > After the initialisation, '->initialized' is to true. > > The raw_spin_lock is only acquired if '->initialized' is > set to true. The worqueue item is only used if 'rcu_scheduler_active' > set to RCU_SCHEDULER_RUNNING which happens after initialisation. > > Use a static initializer for krc.lock and remove the runtime > initialisation of the lock. Since the lock can now be always > acquired, remove the '->initialized' check. > > Signed-off-by: Sebastian Andrzej Siewior > Signed-off-by: Uladzislau Rezki (Sony) > --- > kernel/rcu/tree.c | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index bc6c2bc8fa32..89e9ca3f4e3e 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2892,7 +2892,7 @@ struct kfree_rcu_cpu_work { > * @lock: Synchronize access to this structure > * @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES > * @monitor_todo: Tracks whether a @monitor_work delayed work is pending > - * @initialized: The @lock and @rcu_work fields have been initialized > + * @initialized: The @rcu_work fields have been initialized > * > * This is a per-CPU structure. The reason that it is not included in > * the rcu_data structure is to permit this code to be extracted from > @@ -2912,7 +2912,9 @@ struct kfree_rcu_cpu { > int count; > }; > > -static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc); > +static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = { > + .lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock), > +}; > > static __always_inline void > debug_rcu_bhead_unqueue(struct kfree_rcu_bulk_data *bhead) > @@ -2930,10 +2932,9 @@ krc_this_cpu_lock(unsigned long *flags) > { > struct kfree_rcu_cpu *krcp; > > - local_irq_save(*flags); // For safely calling this_cpu_ptr(). > + local_irq_save(*flags); /* For safely calling this_cpu_ptr(). */ And here as well. ;-) Thanx, Paul > krcp = this_cpu_ptr(&krc); > - if (likely(krcp->initialized)) > - raw_spin_lock(&krcp->lock); > + raw_spin_lock(&krcp->lock); > > return krcp; > } > @@ -2941,8 +2942,7 @@ krc_this_cpu_lock(unsigned long *flags) > static inline void > krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags) > { > - if (likely(krcp->initialized)) > - raw_spin_unlock(&krcp->lock); > + raw_spin_unlock(&krcp->lock); > local_irq_restore(flags); > } > > @@ -4168,7 +4168,6 @@ static void __init kfree_rcu_batch_init(void) > for_each_possible_cpu(cpu) { > struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); > > - raw_spin_lock_init(&krcp->lock); > for (i = 0; i < KFREE_N_BATCHES; i++) { > INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work); > krcp->krw_arr[i].krcp = krcp; > -- > 2.20.1 >