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=-10.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,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 CE949C43441 for ; Mon, 26 Nov 2018 11:04:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9841C21479 for ; Mon, 26 Nov 2018 11:04:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Qr5O9KAm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9841C21479 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730646AbeKZV6l (ORCPT ); Mon, 26 Nov 2018 16:58:41 -0500 Received: from mail.kernel.org ([198.145.29.99]:44050 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726307AbeKZV6k (ORCPT ); Mon, 26 Nov 2018 16:58:40 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 862092089F; Mon, 26 Nov 2018 11:04:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1543230294; bh=PPssmZnB4ckM8MsehMVvkmGb7GRpe1KYmV9ODtLmfAM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Qr5O9KAmIyxQoGl6Cvqqgc9VnpnBk1j4xQJGrUG1fIzFomtXasMK3kke+8xrFRX2/ SSmT9XFVg4DH2KtUmK486wf9jCH5Bdew1OucK7VcOq1+QHvtBEVK2zaSD5A3azBuqK NhvcegBTj57ea3pykeWVN6V5w5muceKv3AhqA1aI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sudeep Holla , Valentin Schneider , "Peter Zijlstra (Intel)" , Dietmar.Eggemann@arm.com, Linus Torvalds , Thomas Gleixner , morten.rasmussen@arm.com, quentin.perret@arm.com, Ingo Molnar , Sasha Levin Subject: [PATCH 4.19 074/118] sched/core: Take the hotplug lock in sched_init_smp() Date: Mon, 26 Nov 2018 11:51:08 +0100 Message-Id: <20181126105104.412501387@linuxfoundation.org> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20181126105059.832485122@linuxfoundation.org> References: <20181126105059.832485122@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 40fa3780bac2b654edf23f6b13f4e2dd550aea10 ] When running on linux-next (8c60c36d0b8c ("Add linux-next specific files for 20181019")) + CONFIG_PROVE_LOCKING=y on a big.LITTLE system (e.g. Juno or HiKey960), we get the following report: [ 0.748225] Call trace: [ 0.750685] lockdep_assert_cpus_held+0x30/0x40 [ 0.755236] static_key_enable_cpuslocked+0x20/0xc8 [ 0.760137] build_sched_domains+0x1034/0x1108 [ 0.764601] sched_init_domains+0x68/0x90 [ 0.768628] sched_init_smp+0x30/0x80 [ 0.772309] kernel_init_freeable+0x278/0x51c [ 0.776685] kernel_init+0x10/0x108 [ 0.780190] ret_from_fork+0x10/0x18 The static_key in question is 'sched_asym_cpucapacity' introduced by commit: df054e8445a4 ("sched/topology: Add static_key for asymmetric CPU capacity optimizations") In this particular case, we enable it because smp_prepare_cpus() will end up fetching the capacity-dmips-mhz entry from the devicetree, so we already have some asymmetry detected when entering sched_init_smp(). This didn't get detected in tip/sched/core because we were missing: commit cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations") Calls to build_sched_domains() post sched_init_smp() will hold the hotplug lock, it just so happens that this very first call is a special case. As stated by a comment in sched_init_smp(), "There's no userspace yet to cause hotplug operations" so this is a harmless warning. However, to both respect the semantics of underlying callees and make lockdep happy, take the hotplug lock in sched_init_smp(). This also satisfies the comment atop sched_init_domains() that says "Callers must hold the hotplug lock". Reported-by: Sudeep Holla Tested-by: Sudeep Holla Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Cc: Dietmar.Eggemann@arm.com Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: morten.rasmussen@arm.com Cc: quentin.perret@arm.com Link: http://lkml.kernel.org/r/1540301851-3048-1-git-send-email-valentin.schneider@arm.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/core.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ad97f3ba5ec5..35551110d277 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5854,11 +5854,14 @@ void __init sched_init_smp(void) /* * There's no userspace yet to cause hotplug operations; hence all the * CPU masks are stable and all blatant races in the below code cannot - * happen. + * happen. The hotplug lock is nevertheless taken to satisfy lockdep, + * but there won't be any contention on it. */ + cpus_read_lock(); mutex_lock(&sched_domains_mutex); sched_init_domains(cpu_active_mask); mutex_unlock(&sched_domains_mutex); + cpus_read_unlock(); /* Move init over to a non-isolated CPU */ if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0) -- 2.17.1