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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B28DDCD6E4A for ; Wed, 3 Jun 2026 06:28:22 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4gVd725wwyz2xc2; Wed, 03 Jun 2026 16:28:14 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=148.163.156.1 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1780468094; cv=none; b=L+bJ/+IhCUZxnUuVNOjeF9y6ax2D8g1YdWtrOajCWI/eo5GXH4zfZ+4B5c1vn8GplkglZhIKpMCgwpzaoMAyrS5tKxkW0ODdp8L+3d9FOgknXwE36ab+x1m3+SyeJk/o3hGo4kt26ZzJhz5EXr+iY9SYvdhyMuHPXBv2i7B3mzvgcERkhNhCMQOEnPbViKm+QjpFsVtSwjRDB2j33mRLTXYNb5HzjqufwGyl/mQpfY1OBg2NiyePkFAOAVjIQF+2WHFYvALGEdFuPSzbyvFFRNEpWNwCj5FcaRD7Kz5EsG1lyfwfWh/TFvY85hXYxY6vRVn23mH0CMJX4urDjvgA2g== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1780468094; c=relaxed/relaxed; bh=5RuyxDjFPIpjwknUPXiV6WeC/V+p6pLbpxglLwF1LmU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LK9jYbpxi0Gt9mIwhpRy8yobc17+kEBLz8wuPnXAA4AIw0H81yJt/+DTpHqae4SwUN7igHoMISeZFLvoqnxE72AGTgMaWREXNF9Y39wSivYBsJNrNUqlDYGxTEeSDgwCSuRmzc5p64JKrQktnjZZoC/oB8ksbA+Em3V2iwS1PwsFAXOh+7wwg0xWRulOQv2D1iFisb9p/f2oeX7DLmL6ciG5ryLm551kYY9m5EXhK0dlWCb8XuJ4Rlm6f3H2eir1J3TMIAH8HGdFygs9m8jSVx1FVPn3VLCwAGH1ueqmHITheS6uOnWalTrmyMlbnC7NKYBieZtp2WC8GyLiIxozUg== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=FGxCSZuZ; dkim-atps=neutral; spf=pass (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=aboorvad@linux.ibm.com; receiver=lists.ozlabs.org) smtp.mailfrom=linux.ibm.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=FGxCSZuZ; dkim-atps=neutral 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=aboorvad@linux.ibm.com; receiver=lists.ozlabs.org) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (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 lists.ozlabs.org (Postfix) with ESMTPS id 4gVd713V1Vz2ySl for ; Wed, 03 Jun 2026 16:28:13 +1000 (AEST) Received: from pps.filterd (m0353729.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 653669BW2897645; Wed, 3 Jun 2026 06:28:10 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:date:from:in-reply-to:message-id :mime-version:references:subject:to; s=pp1; bh=5RuyxDjFPIpjwknUP XiV6WeC/V+p6pLbpxglLwF1LmU=; b=FGxCSZuZhEGWpFGdLnc/owU60pU/5LiLL LONOZF7LToiDaQsxs7ENuj24iF2GROGc9HWUrq+6eCfiFmXIzKvrZiW1ErGpnUdm 7nQoXTNrFoGfG98Y+CUDTeUrLp5Z/M/yGsiy6PPR0cEe7qyEEq9wFnSJqfT40fob D2t0HxVew2t4PMCy+51Wh685y/EuTNHdpLtXlRPtURyKoB9IjhOl4AtH7cUfeWJe 1MVzjoDrDMur1H6gBRChUCod3t8+wMSR9uBwIzo5SwP6ZHSOK8LSEBmGWFKvDNZN gsyMXyKpfwrDiXFhIa6NNneh6WW1/uT1C4U5Lh15xZX76mJUeBgBg== Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4efqjq9f9w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 03 Jun 2026 06:28:10 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 6536Oadj022721; Wed, 3 Jun 2026 06:28:09 GMT Received: from smtprelay03.fra02v.mail.ibm.com ([9.218.2.224]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4egakvy04k-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 03 Jun 2026 06:28:09 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 6536S5gb50987502 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 3 Jun 2026 06:28:05 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 224CB20043; Wed, 3 Jun 2026 06:28:05 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DDB3220040; Wed, 3 Jun 2026 06:28:01 +0000 (GMT) Received: from aboo.ibm.com.com (unknown [9.39.24.39]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 3 Jun 2026 06:28:01 +0000 (GMT) From: Aboorva Devarajan To: Madhavan Srinivasan , linuxppc-dev@lists.ozlabs.org Cc: Athira Rajeev , Aboorva Devarajan , Christophe Leroy , linux-kernel@vger.kernel.org, Sourabh Jain , Ritesh Harjani , Shrikanth Hegde Subject: [PATCH 3/3] powerpc/kexec: fix double get_cpu() imbalance in kexec_prepare_cpus Date: Wed, 3 Jun 2026 11:57:43 +0530 Message-ID: <20260603062743.1152253-4-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260603062743.1152253-1-aboorvad@linux.ibm.com> References: <20260603062743.1152253-1-aboorvad@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: yUIY4cDnkKZJp1H322_jgn677HP3tL2k X-Proofpoint-GUID: u7iXvpUrp6lWhCOYoS685Vm5LWcDY0du X-Authority-Analysis: v=2.4 cv=bcVbluPB c=1 sm=1 tr=0 ts=6a1fc97a cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=NZuQ31_9CfGeVvh8xa4A:9 a=O8hF6Hzn-FEA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjAzMDA1NiBTYWx0ZWRfXysn2RhiqjE8Y TzpEo4UPiNtYXhYBF2pXXLCho1VY2q5T8wKSi+iazq5fq1fQq3rmoPtIMZgiWV9ltGd7UPhe/wi YXqxSvk0s41cfCDGTdU3aW8xV38oQ6bGR+GyDPwQ3zvaOOPRF6nxChXH/awc3rlryGu+nKArY0S 5eqFYaurM/LNmJ24HGrcYS5N3zIaNkSAkS03eHdYDNFA4rocy/LgPwR31gwQwEeYLRISusc157V gl2pEg1YvWJfJB8ELREl9uTQYS6VigK0wv3iE9WDj7YTccT9MCkZ/8stybQsAq9Y6klLedzxGfv H9w6ZlqCkajilGLFT4yMCYbRuq8ZPV0+vH418p7oSLWMWHwa5jfR+q/Pw8bSJxobJf20urKWTk9 TiKAqNVGz7g6lQzmDNP5XADIrjj4eDj5LTr8AhOWDuv2puIPZqqkiJDC1ViZ3M7gyAZSzXoQU05 Jx7zER+aHgwy6s28aBA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-03_02,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1015 adultscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606030056 kexec_prepare_cpus_wait() calls get_cpu() internally to obtain the current CPU id. kexec_prepare_cpus() calls kexec_prepare_cpus_wait() twice -- once for KEXEC_STATE_IRQS_OFF and once for KEXEC_STATE_REAL_MODE -- but only issues a single put_cpu() at the end, leaving preempt_count elevated by one extra nesting level. In practice the imbalance does not trigger a 'scheduling while atomic' splat because the kexec path is a one-way trip: IRQs are already disabled, no schedule() occurs after the leak, and default_machine_kexec() overwrites preempt_count with HARDIRQ_OFFSET before jumping into kexec_sequence() which never returns. However the bookkeeping is still wrong. kexec_prepare_cpus() calls local_irq_disable()/hard_irq_disable() before invoking kexec_prepare_cpus_wait(), so the CPU is already pinned and the get_cpu()/put_cpu() preempt_disable() bracketing is unnecessary. Only the current CPU id is needed, so replace get_cpu() with smp_processor_id() and drop the now-unneeded put_cpu(). Fixes: 1fc711f7ffb0 ("powerpc/kexec: Fix race in kexec shutdown") Signed-off-by: Aboorva Devarajan --- arch/powerpc/kexec/core_64.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c index 825ab8a88f18..d7bdc362d497 100644 --- a/arch/powerpc/kexec/core_64.c +++ b/arch/powerpc/kexec/core_64.c @@ -169,7 +169,7 @@ static void kexec_prepare_cpus_wait(int wait_state) int my_cpu, i, notified=-1; hw_breakpoint_disable(); - my_cpu = get_cpu(); + my_cpu = smp_processor_id(); /* Make sure each CPU has at least made it to the state we need. * * FIXME: There is a (slim) chance of a problem if not all of the CPUs @@ -267,8 +267,6 @@ static void kexec_prepare_cpus(void) /* after we tell the others to go down */ if (ppc_md.kexec_cpu_down) ppc_md.kexec_cpu_down(0, 0); - - put_cpu(); } #else /* ! SMP */ -- 2.54.0