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 45502C433EF for ; Wed, 20 Apr 2022 18:17:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381459AbiDTSTq (ORCPT ); Wed, 20 Apr 2022 14:19:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233570AbiDTSTo (ORCPT ); Wed, 20 Apr 2022 14:19:44 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DE519FD3; Wed, 20 Apr 2022 11:16:57 -0700 (PDT) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 23KI0shV020011; Wed, 20 Apr 2022 18:16:46 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=pp1; bh=8uhPUsPO5Owws7Bjf6Vxskq3KKfsHHNUxbKMMmLdx1w=; b=dD9snOoj4/Mxwdxj8LyF7NCKVbgAb4Ho82D65ezMhtMUp/YkYJGJVKxaFVA5b8BAm2g5 dy4AJKj4EfrqSHyHflSBFgSSYvGut5wU+c53f9GapKA6Wt9aJlO/Ss7pTn4gbZzxHrVY eZaKu0yT3wZUWyX0+/duP7RBufYMFpybihsxnHpbr4pz+me/ChUO7DEKLjWrg+sU05IX 1ax6c2mcrF1zPqmGCsrDIyvR+BPEHDXsGe0gzTMsTO3OlvfzlA+0dCOJRzj/je5RNUTk rmMWh8Wy57gS1FYmxv3etJaX4LUvXZt/kCdJeIYq+7jLR2tRh24sFGvHzpHojrkwtUnM FA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3fjm2hd514-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 20 Apr 2022 18:16:45 +0000 Received: from m0098410.ppops.net (m0098410.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 23KIGjQq020248; Wed, 20 Apr 2022 18:16:45 GMT Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com with ESMTP id 3fjm2hd50g-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 20 Apr 2022 18:16:45 +0000 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 23KIEACN029771; Wed, 20 Apr 2022 18:16:43 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma06ams.nl.ibm.com with ESMTP id 3ffn2hxqh3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 20 Apr 2022 18:16:42 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 23KIGdr551118570 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Apr 2022 18:16:39 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ACA84A405F; Wed, 20 Apr 2022 18:16:39 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 54986A405C; Wed, 20 Apr 2022 18:16:39 +0000 (GMT) Received: from osiris (unknown [9.145.42.46]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Wed, 20 Apr 2022 18:16:39 +0000 (GMT) Date: Wed, 20 Apr 2022 20:16:37 +0200 From: Heiko Carstens To: Pingfan Liu Cc: linux-s390@vger.kernel.org, Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/9] s390/irq: utilize RCU instead of irq_lock_sparse() in show_msi_interrupt() Message-ID: References: <20220420140521.45361-1-kernelfans@gmail.com> <20220420140521.45361-5-kernelfans@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220420140521.45361-5-kernelfans@gmail.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: Tmdi8VJ_xmfYAKJR6QOD66jCxD7Tamwm X-Proofpoint-ORIG-GUID: 5YrumQ7X8EDTWkf9JoF7AxUiYVLL9Ho- X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-04-20_05,2022-04-20_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1011 lowpriorityscore=0 adultscore=0 suspectscore=0 mlxlogscore=658 spamscore=0 bulkscore=0 phishscore=0 malwarescore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2204200107 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 20, 2022 at 10:05:16PM +0800, Pingfan Liu wrote: > irq_desc can be accessed safely in RCU read section as demonstrated by > kstat_irqs_usr(). And raw_spin_lock_irqsave() context can provide a rcu > read section, which can be utilized to get rid of irq_lock_sparse(). > > Signed-off-by: Pingfan Liu > Cc: Heiko Carstens > Cc: Vasily Gorbik > Cc: Alexander Gordeev > Cc: Christian Borntraeger > Cc: Sven Schnelle > Cc: Sebastian Andrzej Siewior > Cc: linux-kernel@vger.kernel.org > To: linux-s390@vger.kernel.org > --- > arch/s390/kernel/irq.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c > index 3033f616e256..6302dc7874cf 100644 > --- a/arch/s390/kernel/irq.c > +++ b/arch/s390/kernel/irq.c > @@ -205,12 +205,13 @@ static void show_msi_interrupt(struct seq_file *p, int irq) > unsigned long flags; > int cpu; > > - irq_lock_sparse(); > + raw_spin_lock_irqsave(&desc->lock, flags); > desc = irq_to_desc(irq); How is this supposed to work? desc get's initialized after its random stack value has been used as a pointer to lock something...