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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 AC007C432C0 for ; Tue, 19 Nov 2019 14:38:54 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 60B7922316 for ; Tue, 19 Nov 2019 14:38:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60B7922316 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47HT3J4HhhzDqgn for ; Wed, 20 Nov 2019 01:38:52 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=fbarrat@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47HT0w6K5JzDq9y for ; Wed, 20 Nov 2019 01:36:48 +1100 (AEDT) Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id xAJELvpW007080 for ; Tue, 19 Nov 2019 09:36:46 -0500 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2wadmx19ba-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 19 Nov 2019 09:36:41 -0500 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 19 Nov 2019 14:36:28 -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 xAJEaRUw56098858 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 19 Nov 2019 14:36:27 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4E591A405B; Tue, 19 Nov 2019 14:36:27 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0C7E1A405C; Tue, 19 Nov 2019 14:36:27 +0000 (GMT) Received: from bali.tlslab.ibm.com (unknown [9.101.4.17]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 19 Nov 2019 14:36:26 +0000 (GMT) Subject: Re: [PATCH 02/11] powerpc/powernv/ioda: Protect PE list To: "Oliver O'Halloran" References: <20190909154600.19917-1-fbarrat@linux.ibm.com> <20190909154600.19917-3-fbarrat@linux.ibm.com> <8f5d581d8f1e8defaf8622cd79c40c98f18d3507.camel@au1.ibm.com> <882c0d26-7931-a2e9-c99a-7732d32a6a2f@linux.ibm.com> From: Frederic Barrat Date: Tue, 19 Nov 2019 15:36:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19111914-4275-0000-0000-00000382647D X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19111914-4276-0000-0000-00003895D8DE Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-19_04:2019-11-15,2019-11-19 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 mlxlogscore=806 impostorscore=0 mlxscore=0 clxscore=1015 priorityscore=1501 spamscore=0 suspectscore=0 lowpriorityscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911190133 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Christophe Lombard , linuxppc-dev , Alastair D'Silva , Andrew Donnellan , Greg Kurz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 19/11/2019 à 14:22, Oliver O'Halloran a écrit : > On Tue, Nov 19, 2019 at 11:57 PM Frederic Barrat wrote: >> >>> Do the other accessors of ioda.pe_list also need mutex protection? >>> pnv_ioda_setup_bus_PE() >>> pnv_pci_dma_bus_setup() >>> pnv_pci_init_ioda_phb() >>> pnv_pci_ioda_setup_PEs() >> >> >> I think we could also use it there, it wouldn't hurt. Those functions >> are called when the kernel is building part of the PCI topology, and >> devices are not really active yet, so I don't think it's absolutely >> required. >> >> I'm actually not sure my patch is needed either. With hotplug, the >> devices can come and go, whereas the PHB remains. So it feels right to >> start protecting the list when adding/removing a device. But I don't >> think we can really have concurrency and have 2 different operations >> adding/removing devices at the same time under the same PHB, at least >> for opencapi. Maybe for PCI, if we have multiple slots under the same >> PHB. Not sure. > > Creation of new pci_dev's is serialised by the global pci rescan and > remove lock so on the creation side it's not an issue. However, we can > release IODA PEs in the pci_dev's release function which might be > called without that lock held. It's pretty hard to hit that case > though since it require something to be holding a ref to the pci_dev > even after the driver's ->remove() function has been called. Thanks for clarifying it! Indeed, the pci_rescan_remove_lock in hotplug helps for the PCI case. I guess we can keep this patch for that hard to hit case, just in case it doesn't blow up somewhere else. Fred