From patchwork Mon Dec 19 20:29:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Elliott, Robert (Servers)" X-Patchwork-Id: 13077129 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 342CEC4332F for ; Mon, 19 Dec 2022 20:30:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232471AbiLSUaV (ORCPT ); Mon, 19 Dec 2022 15:30:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232641AbiLSUaD (ORCPT ); Mon, 19 Dec 2022 15:30:03 -0500 Received: from mx0a-002e3701.pphosted.com (mx0a-002e3701.pphosted.com [148.163.147.86]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18B488FCC; Mon, 19 Dec 2022 12:29:58 -0800 (PST) Received: from pps.filterd (m0134422.ppops.net [127.0.0.1]) by mx0b-002e3701.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 2BJKRChb029372; Mon, 19 Dec 2022 20:29:44 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=hpe.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=pps0720; bh=jD3LLgSm37nQRHMfKV4CUST8QKYllFqCcPy8zK6SIaM=; b=RyEzalHhrx/aHW3orjqb8LBtPsIHKMSwHC0xpg9eaj/HNB2G6wFZy4pO5S/S8fd+oerW wmCJvFkeF7AxHxMq//9NyHmZM+gepIK8w5ZpT6mPKBLhtknXQLmZruX1Kq+Qo21mbkgo a+zmJ35F2pbb1rSjMZK3zyZtN9egQnXbcluUmf3axRXe/CU1Urc9OltNUTn2EFk9cD96 WyL73c+6rrltYL9kqMV9A2g1Lk/6u51nTSi91Lpg1BWWzjmX4g7QwOL6EJL6VQGiF7tn gFAT7GoqnNyS9arIrU+H2L6n0Y7MKQuLl921TyI0Rl2Cbhr52HHp3B5kNJeDWxVT8YNv 9g== Received: from p1lg14880.it.hpe.com (p1lg14880.it.hpe.com [16.230.97.201]) by mx0b-002e3701.pphosted.com (PPS) with ESMTPS id 3mjy0fr0hu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 19 Dec 2022 20:29:44 +0000 Received: from p1lg14885.dc01.its.hpecorp.net (unknown [10.119.18.236]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by p1lg14880.it.hpe.com (Postfix) with ESMTPS id 877EC807EE5; Mon, 19 Dec 2022 20:29:43 +0000 (UTC) Received: from adevxp033-sys.us.rdlabs.hpecorp.net (unknown [16.231.227.36]) by p1lg14885.dc01.its.hpecorp.net (Postfix) with ESMTP id 1DC488065EB; Mon, 19 Dec 2022 20:29:43 +0000 (UTC) From: Robert Elliott To: herbert@gondor.apana.org.au, davem@davemloft.net, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org Cc: linux-crypto@vger.kernel.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Robert Elliott Subject: [PATCH 2/3] rcu: print first CPU on expedited stall line Date: Mon, 19 Dec 2022 14:29:09 -0600 Message-Id: <20221219202910.3063036-3-elliott@hpe.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221219202910.3063036-1-elliott@hpe.com> References: <20221219202910.3063036-1-elliott@hpe.com> MIME-Version: 1.0 X-Proofpoint-ORIG-GUID: wSTApf6gnSbNoJkuVG0vozCGTGg8BbvZ X-Proofpoint-GUID: wSTApf6gnSbNoJkuVG0vozCGTGg8BbvZ X-HPE-SCL: -1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-12-19_01,2022-12-15_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 malwarescore=0 clxscore=1015 impostorscore=0 phishscore=0 lowpriorityscore=0 mlxlogscore=812 mlxscore=0 bulkscore=0 priorityscore=1501 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2212190180 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Include the first CPU number in the first pr_err() call reporting an expedited stall warning. Printing the CPU numbers with subsequent pr_cont() calls can result in the prints being many lines away or being dropped entirely in a busy system. This change ensures there is indication of at least one of the CPUs with the problem with the original message. Before (if prints are interspersed with other prints): rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 13-.... } 32 jiffies s: 6685 root: 0x1/. After: rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: {13-.... } 32 jiffies s: 6685 root: 0x1/. Signed-off-by: Robert Elliott --- kernel/rcu/tree_exp.h | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index ed6c3cce28f2..ade6a18e6c07 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -624,8 +624,6 @@ static void synchronize_rcu_expedited_wait(void) if (rcu_stall_is_suppressed()) continue; trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall")); - pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {", - rcu_state.name); ndetected = 0; rcu_for_each_leaf_node(rnp) { ndetected += rcu_print_task_exp_stall(rnp); @@ -637,11 +635,21 @@ static void synchronize_rcu_expedited_wait(void) continue; ndetected++; rdp = per_cpu_ptr(&rcu_data, cpu); - pr_cont(" %d-%c%c%c%c", cpu, - "O."[!!cpu_online(cpu)], - "o."[!!(rdp->grpmask & rnp->expmaskinit)], - "N."[!!(rdp->grpmask & rnp->expmaskinitnext)], - "D."[!!(rdp->cpu_no_qs.b.exp)]); + // print the prefix and the first CPU number together + // under heavy load, the pr_cont prints can be far away or dropped + if (ndetected == 1) + pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {%d-%c%c%c%c", + rcu_state.name, cpu, + "O."[!!cpu_online(cpu)], + "o."[!!(rdp->grpmask & rnp->expmaskinit)], + "N."[!!(rdp->grpmask & rnp->expmaskinitnext)], + "D."[!!(rdp->cpu_no_qs.b.exp)]); + else + pr_cont(" %d-%c%c%c%c", cpu, + "O."[!!cpu_online(cpu)], + "o."[!!(rdp->grpmask & rnp->expmaskinit)], + "N."[!!(rdp->grpmask & rnp->expmaskinitnext)], + "D."[!!(rdp->cpu_no_qs.b.exp)]); } } pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",