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,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 6B5E3C4742C for ; Thu, 5 Nov 2020 23:49:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20BE220756 for ; Thu, 5 Nov 2020 23:49:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604620141; bh=RmqrHKJx6BYaq4MH6bNxDrXByH53ETHnBnon0isWHcQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=hPZMc8Fceuc8XRt+1yoIZHXaUKk0xOH1IBeqH1HG4LZ/KA1C7dIUkniR93ThN9vtb IH5YPfU/FIlrpw0Lj0kuaIUIrqeyhO7gDkQ8hGllnwecEtsxxAD4S5JlfsKn18mjO4 TIhXq5x/MEFgxvU/gKbOb+c5FJdX2gTSpJ4yDiUg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733163AbgKEXtA (ORCPT ); Thu, 5 Nov 2020 18:49:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:45970 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732498AbgKEXrY (ORCPT ); Thu, 5 Nov 2020 18:47:24 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (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 475A82151B; Thu, 5 Nov 2020 23:47:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604620043; bh=RmqrHKJx6BYaq4MH6bNxDrXByH53ETHnBnon0isWHcQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wfnrowlSUQ7MFGxQWY/ccC/2ZFvl3KPTjqXwT3OYFIfv/YtVUynz/C6e+PQFnw/yW XYgNUhekE1f5eqM2D2SPLkMO++qFi1MYMj/6q8zgDxK1mibDeI+3PV1RsA7NDrJMI7 pBfVKy0RrfZZRIgWPITewVpPirnctRtaimlbjUYQ= 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, 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, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/28] torture: Periodically pause in stutter_wait() Date: Thu, 5 Nov 2020 15:46:55 -0800 Message-Id: <20201105234719.23307-4-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20201105234658.GA23142@paulmck-ThinkPad-P72> References: <20201105234658.GA23142@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Running locktorture scenario LOCK05 results in hangs: tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --torture lock --duration 3 --configs LOCK05 The lock_torture_writer() kthreads set themselves to MAX_NICE while running SCHED_OTHER. Other locktorture kthreads run at default niceness, also SCHED_OTHER. This results in these other locktorture kthreads indefinitely preempting the lock_torture_writer() kthreads. Note that the cond_resched() in the stutter_wait() function's loop is ineffective because this scenario is built with CONFIG_PREEMPT=y. It is not clear that such indefinite preemption is supposed to happen, but in the meantime this commit prevents kthreads running in stutter_wait() from being completely CPU-bound, thus allowing the other threads to get some CPU in a timely fashion. This commit also uses hrtimers to provide very short sleeps to avoid degrading the sudden-on testing that stutter is supposed to provide. Reviewed-by: Davidlohr Bueso Signed-off-by: Paul E. McKenney --- kernel/torture.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/kernel/torture.c b/kernel/torture.c index 1061492..5488ad2 100644 --- a/kernel/torture.c +++ b/kernel/torture.c @@ -602,8 +602,11 @@ static int stutter_gap; */ bool stutter_wait(const char *title) { - int spt; + ktime_t delay; + unsigned i = 0; + int oldnice; bool ret = false; + int spt; cond_resched_tasks_rcu_qs(); spt = READ_ONCE(stutter_pause_test); @@ -612,8 +615,17 @@ bool stutter_wait(const char *title) if (spt == 1) { schedule_timeout_interruptible(1); } else if (spt == 2) { - while (READ_ONCE(stutter_pause_test)) + oldnice = task_nice(current); + set_user_nice(current, MAX_NICE); + while (READ_ONCE(stutter_pause_test)) { + if (!(i++ & 0xffff)) { + set_current_state(TASK_INTERRUPTIBLE); + delay = 10 * NSEC_PER_USEC; + schedule_hrtimeout(&delay, HRTIMER_MODE_REL); + } cond_resched(); + } + set_user_nice(current, oldnice); } else { schedule_timeout_interruptible(round_jiffies_relative(HZ)); } -- 2.9.5