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=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 DB0AEC43613 for ; Fri, 21 Jun 2019 06:07:18 +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 1DCAE2083B for ; Fri, 21 Jun 2019 06:07:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1DCAE2083B 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 45VSrf2fSSzDqby for ; Fri, 21 Jun 2019 16:07:14 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=nathanl@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 45VSpb5VJLzDqbx for ; Fri, 21 Jun 2019 16:05:26 +1000 (AEST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5L5ulhG126033 for ; Fri, 21 Jun 2019 02:05:23 -0400 Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx0a-001b2d01.pphosted.com with ESMTP id 2t8p1cq1sh-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 21 Jun 2019 02:05:22 -0400 Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 21 Jun 2019 07:05:22 +0100 Received: from b03cxnp08026.gho.boulder.ibm.com (9.17.130.18) by e35.co.us.ibm.com (192.168.1.135) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 21 Jun 2019 07:05:20 +0100 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08026.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5L65JKK32113082 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Jun 2019 06:05:19 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EDBC4C6059; Fri, 21 Jun 2019 06:05:18 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BD97EC6055; Fri, 21 Jun 2019 06:05:18 +0000 (GMT) Received: from localhost (unknown [9.85.146.224]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 21 Jun 2019 06:05:18 +0000 (GMT) From: Nathan Lynch To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH] powerpc/rtas: retry when cpu offline races with suspend/migration Date: Fri, 21 Jun 2019 01:05:18 -0500 X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19062106-0012-0000-0000-00001746A009 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011301; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01221045; UDB=6.00642381; IPR=6.01002184; MB=3.00027401; MTD=3.00000008; XFM=3.00000015; UTC=2019-06-21 06:05:21 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19062106-0013-0000-0000-000057C57C4C Message-Id: <20190621060518.29616-1-nathanl@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-06-21_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906210051 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: ego@linux.vnet.ibm.com, mmc@linux.vnet.ibm.com, julietk@linux.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" The protocol for suspending or migrating an LPAR requires all present processor threads to enter H_JOIN. So if we have threads offline, we have to temporarily bring them up. This can race with administrator actions such as SMT state changes. As of dfd718a2ed1f ("powerpc/rtas: Fix a potential race between CPU-Offline & Migration"), rtas_ibm_suspend_me() accounts for this, but errors out with -EBUSY for what almost certainly is a transient condition in any reasonable scenario. Callers of rtas_ibm_suspend_me() already retry when -EAGAIN is returned, and it is typical during a migration for that to happen repeatedly for several minutes polling the H_VASI_STATE hcall result before proceeding to the next stage. So return -EAGAIN instead of -EBUSY when this race is encountered. Additionally: logging this event is still appropriate but use pr_info instead of pr_err; and remove use of unlikely() while here as this is not a hot path at all. Fixes: dfd718a2ed1f ("powerpc/rtas: Fix a potential race between CPU-Offline & Migration") Signed-off-by: Nathan Lynch --- arch/powerpc/kernel/rtas.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index fbc676160adf..9b4d2a2ffb4f 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -984,10 +984,9 @@ int rtas_ibm_suspend_me(u64 handle) cpu_hotplug_disable(); /* Check if we raced with a CPU-Offline Operation */ - if (unlikely(!cpumask_equal(cpu_present_mask, cpu_online_mask))) { - pr_err("%s: Raced against a concurrent CPU-Offline\n", - __func__); - atomic_set(&data.error, -EBUSY); + if (!cpumask_equal(cpu_present_mask, cpu_online_mask)) { + pr_info("%s: Raced against a concurrent CPU-Offline\n", __func__); + atomic_set(&data.error, -EAGAIN); goto out_hotplug_enable; } -- 2.20.1