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=-13.1 required=3.0 tests=BAYES_00,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_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 43047C433E6 for ; Mon, 31 Aug 2020 18:01:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0850D2083E for ; Mon, 31 Aug 2020 18:01:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598896901; bh=/yTUs0FVay3sAqB0eTJiMOJcG5gY0G1ZMAr1sjY9mug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YkpBV6n7lRvFMCATbuNSQPMT07MRVze4deF0K7mE96vfz45VFyuOcjwaOkO8hKbHw 2R+8sKKJ2Tnt6farF9fw2ioDYPs2DlWDqU5JYFl8loFTRA9L3kPaCwmhgk5o9CrwBw YzlYiY+NWHcbEPcgZ7gWj+1IA2qgpXJ5qmBR3pIc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729007AbgHaSBj (ORCPT ); Mon, 31 Aug 2020 14:01:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:35868 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728348AbgHaSBW (ORCPT ); Mon, 31 Aug 2020 14:01:22 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B87B421534; Mon, 31 Aug 2020 18:01:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598896882; bh=/yTUs0FVay3sAqB0eTJiMOJcG5gY0G1ZMAr1sjY9mug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qnwei98lujhVttzUCeKUU0xGi31zidZO/Lm2XPrwytbawfMewQLxQfdY6OMCInimR XFXFquMbwxTfPS1jIEqR745GejCR+25BcsaTtSdpuUA2sTX2JIvzDCELIqaSQD2cN4 eb3rGjzN8wAItKpFxpOqNZiJ+LpDNbfvtfJSYpoY= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Neeraj Upadhyay , "Paul E . McKenney" Subject: [PATCH tip/core/rcu 08/24] rcu/tree: Force quiescent state on callback overload Date: Mon, 31 Aug 2020 11:01:00 -0700 Message-Id: <20200831180116.32690-8-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200831180050.GA32590@paulmck-ThinkPad-P72> References: <20200831180050.GA32590@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Neeraj Upadhyay 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 --- 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 8969120..4770d77 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1884,7 +1884,7 @@ 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); -- 2.9.5