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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 00BECC56202 for ; Tue, 27 Oct 2020 15:08:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B57E22072E for ; Tue, 27 Oct 2020 15:08:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603811285; bh=JXZONq7X0oCbEAnznopNN9JnAMd0U9fKlt09WB8qHoY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lfjFaKi0IlzdIs3JM3Hz1HfpW5Gsx1ZGdd17REcMr6TkA2TgxRCRwSTjXQJQzggZQ GR9nnmcPNUBpd3mwgFcJY0wp6d17XtA7o8uP1Tt7AuBIfGTpF8bAE+gRTZDVCPJCyz ZlbpKCD8rgf/rTW7qDrkJaP+FrSFeAuGVZ4PniYw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1793735AbgJ0PIE (ORCPT ); Tue, 27 Oct 2020 11:08:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:37088 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1789761AbgJ0PCs (ORCPT ); Tue, 27 Oct 2020 11:02:48 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 EB05020747; Tue, 27 Oct 2020 15:02:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603810967; bh=JXZONq7X0oCbEAnznopNN9JnAMd0U9fKlt09WB8qHoY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S71CDBwapHpoHH/erP4HXPrF9B1djl5LCxEntc8Z8K7DsWuyzCk4n2JxcjGvV91qk FYmtwMnHkKXhibR1SbM83dIVkBxht1PiEMhT/Vw3+W6KmmT/sM3VdOsvkjspC3INKF W16XLRn8cEgNlGYN8CcVCUwEJR12VVzHEHhRlhtU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Joel Fernandes (Google)" , Neeraj Upadhyay , "Paul E. McKenney" , Sasha Levin Subject: [PATCH 5.8 327/633] rcu/tree: Force quiescent state on callback overload Date: Tue, 27 Oct 2020 14:51:10 +0100 Message-Id: <20201027135538.021558130@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135522.655719020@linuxfoundation.org> References: <20201027135522.655719020@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Neeraj Upadhyay [ Upstream commit 9c39245382de4d52a122641952900709d4a9950b ] On callback overload, it is necessary to quickly detect idle CPUs, and rcu_gp_fqs_check_wake() checks for this condition. Unfortunately, the code following the call to this function does not repeat this check, which means that in reality no actual quiescent-state forcing, instead only a couple of quick and pointless wakeups at the beginning of the grace period. This commit therefore adds a check for the RCU_GP_FLAG_OVLD flag in the post-wakeup "if" statement in rcu_gp_fqs_loop(). Fixes: 1fca4d12f4637 ("rcu: Expedite first two FQS scans under callback-overload conditions") Reviewed-by: Joel Fernandes (Google) Signed-off-by: Neeraj Upadhyay Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 1e9e500ff7906..572a79b1a8510 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1882,7 +1882,7 @@ static void rcu_gp_fqs_loop(void) break; /* If time for quiescent-state forcing, do it. */ if (!time_after(rcu_state.jiffies_force_qs, jiffies) || - (gf & RCU_GP_FLAG_FQS)) { + (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) { trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("fqsstart")); rcu_gp_fqs(first_gp_fqs); -- 2.25.1