From patchwork Mon Jun 20 22:51:28 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 12888354 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 C0BD5C433EF for ; Mon, 20 Jun 2022 22:51:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243819AbiFTWvh (ORCPT ); Mon, 20 Jun 2022 18:51:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54718 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344175AbiFTWvd (ORCPT ); Mon, 20 Jun 2022 18:51:33 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DB551CB10; Mon, 20 Jun 2022 15:51:32 -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 50B35613F7; Mon, 20 Jun 2022 22:51:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59B5DC341D5; Mon, 20 Jun 2022 22:51:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655765490; bh=oMsHSf3dnE1PCs3K0mPgTlXOBWPjOTVil2QL7Pc287I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tf0sEhNyvz9OwkVPws0rI4VEOFBxn29UvS7QiWe8ip/oReiP4pIWRpTLvr7wFe/A7 T1wfb9cetYPxZzGdN0dP7Mt6EetSEu+EiOFvupeqJyuEUEWinb0X2qflZPg0lgTqHe i3BrbHH0i6e0fPUqVxjgKKqAI5ZQLlD2ytRrYLqmUA0eF9ouJl1PjrCj3H7L8oPvjU gq065X++7ih4athDNH7Z4wHLZnUH5s5Fmwbd3+1+4/lQmSYlnXjvUXUCP3QAIjCD3R S2kjujXAgKbTSufin7CQ72X2rDtAkQacBqiZXGdKZ2qXeno+oyAI1YG/fA4vNkd4DF 4EQYkfsIJhC3A== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id A96045C0E3F; Mon, 20 Jun 2022 15:51:29 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Zqiang , "Paul E . McKenney" Subject: [PATCH rcu 12/12] rcu: Add irqs-disabled indicator to expedited RCU CPU stall warnings Date: Mon, 20 Jun 2022 15:51:28 -0700 Message-Id: <20220620225128.3842050-12-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220620224943.GA3841634@paulmck-ThinkPad-P17-Gen-1> References: <20220620224943.GA3841634@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Zqiang If a CPU has interrupts disabled continuously starting before the beginning of a given expedited RCU grace period, that CPU will not execute that grace period's IPI handler. This will in turn mean that the ->cpu_no_qs.b.exp field in that CPU's rcu_data structure will continue to contain the boolean value false. Knowing whether or not a CPU has had interrupts disabled can be helpful when debugging an expedited RCU CPU stall warning, so this commit adds a "D" indicator expedited RCU CPU stall warnings that signifies that the corresponding CPU has had interrupts disabled throughout. This capability was tested as follows: runqemu kvm slirp nographic qemuparams="-m 4096 -smp 4" bootparams= "isolcpus=2,3 nohz_full=2,3 rcu_nocbs=2,3 rcutree.dump_tree=1 rcutorture.stall_cpu_holdoff=30 rcutorture.stall_cpu=40 rcutorture.stall_cpu_irqsoff=1 rcutorture.stall_cpu_block=0 rcutorture.stall_no_softlockup=1" -d The rcu_torture_stall() function ran on CPU 1, which displays the "D" as expected given the rcutorture.stall_cpu_irqsoff=1 module parameter: ............ rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-...D } 26467 jiffies s: 13317 root: 0x1/. rcu: blocking rcu_node structures (internal RCU debug): l=1:0-1:0x2/. Task dump for CPU 1: task:rcu_torture_sta state:R running task stack: 0 pid: 76 ppid: 2 flags:0x00004008 Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 4c7037b507032..f092c7f18a5f3 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -637,10 +637,11 @@ static void synchronize_rcu_expedited_wait(void) continue; ndetected++; rdp = per_cpu_ptr(&rcu_data, cpu); - pr_cont(" %d-%c%c%c", cpu, + pr_cont(" %d-%c%c%c%c", cpu, "O."[!!cpu_online(cpu)], "o."[!!(rdp->grpmask & rnp->expmaskinit)], - "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]); + "N."[!!(rdp->grpmask & rnp->expmaskinitnext)], + "D."[!!(rdp->cpu_no_qs.b.exp)]); } } pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",