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 42496C433EF for ; Wed, 1 Dec 2021 09:25:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348198AbhLAJ3Q (ORCPT ); Wed, 1 Dec 2021 04:29:16 -0500 Received: from alexa-out-sd-01.qualcomm.com ([199.106.114.38]:10837 "EHLO alexa-out-sd-01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242016AbhLAJ3O (ORCPT ); Wed, 1 Dec 2021 04:29:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1638350753; x=1669886753; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=RuZH4w90n5W5nJ9qxjET1aTW0ME4PBkPQ1uu/8hLefg=; b=pfWFMYuUtp9rcZBTNMuhS0lKMCZlyvoXGnGyAZDxTX+4yDgz6yXAz6da e3m7ssgKDLQWQ1yybSQEjyumLuFcevEFZfYTjIPL3GBfbKGtehb4XdDDF LFPqjJCKrPnBDzp8G8XZFWSa9UcHp1yGwOPqGwV7uw0uLyQbVfPNmdtVA 4=; Received: from unknown (HELO ironmsg05-sd.qualcomm.com) ([10.53.140.145]) by alexa-out-sd-01.qualcomm.com with ESMTP; 01 Dec 2021 01:25:53 -0800 X-QCInternal: smtphost Received: from nasanex01b.na.qualcomm.com ([10.46.141.250]) by ironmsg05-sd.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Dec 2021 01:25:52 -0800 Received: from [10.216.8.32] (10.80.80.8) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.922.19; Wed, 1 Dec 2021 01:25:50 -0800 Message-ID: <4b192489-ed1d-179b-ea35-cc9b23b8f389@quicinc.com> Date: Wed, 1 Dec 2021 14:55:46 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH 2/6] rcu/nocb: Prepare nocb_cb_wait() to start with a non-offloaded rdp Content-Language: en-US To: Frederic Weisbecker , "Paul E . McKenney" CC: LKML , Uladzislau Rezki , Boqun Feng , Josh Triplett , Joel Fernandes , References: <20211123003708.468409-1-frederic@kernel.org> <20211123003708.468409-3-frederic@kernel.org> From: Neeraj Upadhyay In-Reply-To: <20211123003708.468409-3-frederic@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nasanex01b.na.qualcomm.com (10.46.141.250) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/23/2021 6:07 AM, Frederic Weisbecker wrote: > In order to be able to toggle the offloaded state from cpusets, a nocb > kthread will need to be created for all possible CPUs whenever the > "rcu_nocbs=" or "nohz_full=" parameters are passed. > > Therefore nocb_cb_wait() kthread must prepare to start running on a > de-offloaded rdp. Simply move the sleeping condition in the beginning > of the kthread callback is enough to prevent from running callbacks > before the rdp ever becomes offloaded. > > Signed-off-by: Frederic Weisbecker > Cc: Neeraj Upadhyay > Cc: Boqun Feng > Cc: Uladzislau Rezki > Cc: Josh Triplett > Cc: Joel Fernandes > --- Reviewed-by: Neeraj Upadhyay Thanks Neeraj > kernel/rcu/tree_nocb.h | 23 ++++++++++++----------- > 1 file changed, 12 insertions(+), 11 deletions(-) > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index cc1165559177..e1cb06840454 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -797,6 +797,18 @@ static void nocb_cb_wait(struct rcu_data *rdp) > bool can_sleep = true; > struct rcu_node *rnp = rdp->mynode; > > + do { > + swait_event_interruptible_exclusive(rdp->nocb_cb_wq, > + nocb_cb_wait_cond(rdp)); > + > + // VVV Ensure CB invocation follows _sleep test. > + if (smp_load_acquire(&rdp->nocb_cb_sleep)) { // ^^^ > + WARN_ON(signal_pending(current)); > + trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty")); > + } > + } while (!nocb_cb_can_run(rdp)); > + > + > local_irq_save(flags); > rcu_momentary_dyntick_idle(); > local_irq_restore(flags); > @@ -849,17 +861,6 @@ static void nocb_cb_wait(struct rcu_data *rdp) > > if (needwake_state) > swake_up_one(&rdp->nocb_state_wq); > - > - do { > - swait_event_interruptible_exclusive(rdp->nocb_cb_wq, > - nocb_cb_wait_cond(rdp)); > - > - // VVV Ensure CB invocation follows _sleep test. > - if (smp_load_acquire(&rdp->nocb_cb_sleep)) { // ^^^ > - WARN_ON(signal_pending(current)); > - trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty")); > - } > - } while (!nocb_cb_can_run(rdp)); > } > > /* >