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 6A149C433EF for ; Tue, 19 Apr 2022 00:00:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236561AbiDSADR (ORCPT ); Mon, 18 Apr 2022 20:03:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236152AbiDSAC6 (ORCPT ); Mon, 18 Apr 2022 20:02:58 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 172F913CDC; Mon, 18 Apr 2022 17:00:18 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 758FC612A0; Tue, 19 Apr 2022 00:00:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EAE3C385B4; Tue, 19 Apr 2022 00:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650326416; bh=d8BookNJh/O4qU39WT4SVwBgry0u2pt1lr7SQzvjnkA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NTmmCdR/7pN5hzrQK2g+6jsxLyKLU+7QwtwM+OzzNSX3KNYpZPdA3BqGL/NEypEhZ wI18v5qZESaM1SFEBTKsgIPmDOfkmjSoR5I1qFpbOO4BsNglKmgPo37SfTWbxjGiwi alMc4vTUdNB0mKBxmrPt2ygaONntkH9q2v5jsGP/ojmu51XbTR/tWEYGNPrAZN6S6b 3lhGhOKz/OtDxBOxAu5vwy8bj7huAGyZ4tsW7U87iTY2Wy8MK8LNYBRgKrYvlI5xxw sLfcSZGbyNRwL9UqboiohZOSN3O3JjVc/E+fxc14EP3tIXC9gENeQ21jfvFsN1Rh68 iPAx3FGXDSCvQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id E12025C0B86; Mon, 18 Apr 2022 17:00:15 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, "Paul E. McKenney" Subject: [PATCH rcu 6/9] rcu-tasks: Restore use of timers for non-RT kernels Date: Mon, 18 Apr 2022 17:00:11 -0700 Message-Id: <20220419000014.3948512-6-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220419000007.GA3945818@paulmck-ThinkPad-P17-Gen-1> References: <20220419000007.GA3945818@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The use of hrtimers for RCU-tasks grace-period delays works well in general, but can result in excessive grace-period delays for some corner-case workloads. This commit therefore reverts to the use of timers for non-RT kernels to mitigate those grace-period delays. Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 71fe340ab82a..405614039515 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -654,9 +654,13 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp) // Slowly back off waiting for holdouts set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS); - exp = jiffies_to_nsecs(fract); - __set_current_state(TASK_IDLE); - schedule_hrtimeout_range(&exp, jiffies_to_nsecs(HZ / 2), HRTIMER_MODE_REL_HARD); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { + schedule_timeout_idle(fract); + } else { + exp = jiffies_to_nsecs(fract); + __set_current_state(TASK_IDLE); + schedule_hrtimeout_range(&exp, jiffies_to_nsecs(HZ / 2), HRTIMER_MODE_REL_HARD); + } if (fract < HZ) fract++; -- 2.31.1.189.g2e36527f23