From nobody Fri Jun 19 17:02:52 2026 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 D4BB2C433EF for ; Thu, 31 Mar 2022 15:44:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238889AbiCaPp4 (ORCPT ); Thu, 31 Mar 2022 11:45:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239309AbiCaPpU (ORCPT ); Thu, 31 Mar 2022 11:45:20 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D5D431E31B0 for ; Thu, 31 Mar 2022 08:39:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648741173; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=HGNBKdVLy2ioTvnPQV3bpsQMS1zK36BBjUbEXrjr8xA=; b=LvacF2X0xAW2dhk8h98FedMx/VWzJaZfjCRUldlRXtunvcJm0LgKfdy02xooqMoC6DIAsR SF0K2w/It4//6Svxcbw3tIprr+x4jNOYZ0xiU7YxBsnr+hToGDkSopfkvJ6C053SlbpXVf ik8Yry9M4DIG6f+E+AiEeEbiAZOeLQs= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-477-TAsf-1w-MVWchVhuC-zIDw-1; Thu, 31 Mar 2022 11:39:28 -0400 X-MC-Unique: TAsf-1w-MVWchVhuC-zIDw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 969213C16193; Thu, 31 Mar 2022 15:39:27 +0000 (UTC) Received: from pauld.bos.com (dhcp-17-51.bos.redhat.com [10.18.17.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5CAF7400E42D; Thu, 31 Mar 2022 15:39:27 +0000 (UTC) From: Phil Auld To: linux-kernel@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Mark Rutland , Peter Zijlstra , linux-arm-kernel@lists.infradead.org, Dietmar Eggemann Subject: [PATCH v3] arch/arm64: Fix topology initialization for core scheduling Date: Thu, 31 Mar 2022 11:39:26 -0400 Message-Id: <20220331153926.25742-1-pauld@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Arm64 systems rely on store_cpu_topology() to call update_siblings_masks() to transfer the toplogy to the various cpu masks. This needs to be done=20 before the call to notify_cpu_starting() which tells the scheduler about=20 each cpu found, otherwise the core scheduling data structures are setup=20 in a way that does not match the actual topology. With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) =3D= =3D 1`=20 for !leaders in: notify_cpu_starting() cpuhp_invoke_callback_range() sched_cpu_starting() sched_core_cpu_starting() which leads to rq->core not being correctly set for !leader-rq's. Without this change stress-ng (which enables core scheduling in its prctl=20 tests in newer versions -- i.e. with PR_SCHED_CORE support) causes a warnin= g=20 and then a crash (trimmed for legibility): [ 1853.805168] ------------[ cut here ]------------ [ 1853.809784] task_rq(b)->core !=3D rq->core [ 1853.809792] WARNING: CPU: 117 PID: 0 at kernel/sched/fair.c:11102 cfs_pr= io_less+0x1b4/0x1c4 ... [ 1854.015210] Unable to handle kernel NULL pointer dereference at virtual = address 0000000000000010 ... [ 1854.231256] Call trace: [ 1854.233689] pick_next_task+0x3dc/0x81c [ 1854.237512] __schedule+0x10c/0x4cc [ 1854.240988] schedule_idle+0x34/0x54 Fixes: 9edeaea1bc45 ("sched: Core-wide rq->lock") Signed-off-by: Phil Auld Reviewed-by: Dietmar Eggemann Tested-by: Dietmar Eggemann --- This is a similar issue to=20 f2703def339c ("MIPS: smp: fill in sibling and core maps earlier")=20 which fixed it for MIPS.=20 v2: Fixed the commit message. No code change. arch/arm64/kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 27df5c1e6baa..3b46041f2b97 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -234,6 +234,7 @@ asmlinkage notrace void secondary_start_kernel(void) * Log the CPU info before it is marked online and might get read. */ cpuinfo_store_cpu(); + store_cpu_topology(cpu); =20 /* * Enable GIC and timers. @@ -242,7 +243,6 @@ asmlinkage notrace void secondary_start_kernel(void) =20 ipi_setup(cpu); =20 - store_cpu_topology(cpu); numa_add_cpu(cpu); =20 /* --=20 2.18.0