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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 AACF9C76191 for ; Thu, 25 Jul 2019 12:56:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6C399218EA for ; Thu, 25 Jul 2019 12:56:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C399218EA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F1A2F8E0071; Thu, 25 Jul 2019 08:56:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EA4578E0059; Thu, 25 Jul 2019 08:56:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D6BC78E0071; Thu, 25 Jul 2019 08:56:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 862FE8E0059 for ; Thu, 25 Jul 2019 08:56:38 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id e9so20965939edv.18 for ; Thu, 25 Jul 2019 05:56:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :in-reply-to:user-agent; bh=WzbRpiXeNAPRf1WNpmRGk/SjiXKIj5CDvJcpUk0ckME=; b=I3FA34c8g5cWYvaVA5tVeJ/UG20a2gET9C030v5L+rDuuM6nvUS0kYt5P8YeP8486N qrC1cgIXkcuEdcTp2wO58XVzDSiRqKYkn6nvUvYYxso+FCd2xAbrAzF/WcLBsddFOeIr 5KYvY6jcjdguG6nSOZHnPHwciqt/7xrpD6IlJNLdPAGtX1Wdj9M9Y/sxvC5AUWzHNosL fQVUk28gowpBcJ7lN5TLR/RVBG9nEFFLz0UGciY+9ir+5xIe2sw5LnVpoax4gNBt+Mt9 FoxRnHPXsVVjdDD5vT/3eHTxkITdx3QAOgy3XRxSupPhUJjJ98e8w0vjq8QSYsMpn3Wr Wddg== X-Original-Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Gm-Message-State: APjAAAU2uMGKrB8xpeUyKikfW32K4xFaPPmViYPfXDANTHE7yL65cIHk 2cXAypZNp5amaowdcN0MBTEGOdJ/GpG0YQVG2lSNK2Nwo7wIapzL1XBifeOjF2kOiSEsuQOw0D0 wJxxgDbeWILbNIDSnBsFlypl0/DFEq7FqofdU/UPq21b4abQaZmF51mMNYEsC18I= X-Received: by 2002:a50:e718:: with SMTP id a24mr75776053edn.91.1564059398102; Thu, 25 Jul 2019 05:56:38 -0700 (PDT) X-Google-Smtp-Source: APXvYqysfu80qhwNwIwRDOLFzXGeMkk9lvkgXOik/9my0VMKzqRfQEz+d6a9p22ozhnocnfxuESR X-Received: by 2002:a50:e718:: with SMTP id a24mr75776009edn.91.1564059397402; Thu, 25 Jul 2019 05:56:37 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1564059397; cv=none; d=google.com; s=arc-20160816; b=1JJwAtKlQwHIXYp5EzLtp9VfftOkoHB54EYV9Tj48QmN3C5Gx2lGZffkG77WOBLLWG A7DCPS0cYOIxb8ZrfmXPART67bdH89YZzzxrseBcdUV0zfFhiUQQaCcicHoFTfrqoI11 URA++VPubd7OiEWYQWn1bGaXgq7yYjHe0i3+Uo+G4NJ3aDn+Nxv4SM6F0WNkNTmAVqpO vs4hF6SkpM6zKUsjLXWEHjUufwM14Ngno0Ja3W+WlmaycV63BVdwIsBhhUrbzF+sysSe mj8PBVohBTHTyWbxKHPW5jIgaCYwXv7K8P1L6cPN2fO0Yiq4/VrKYXYjGjmy+p8m0ExI GDRw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date; bh=WzbRpiXeNAPRf1WNpmRGk/SjiXKIj5CDvJcpUk0ckME=; b=082inDi7FMZS3NQqSZz6SaYW+lF6ts5p/NOUvCP+B27IMS8+vr1c8cxt6ZT7xRr6Qx M4/6r5Hrc/2a40D2C4TCZ4ET1Wet/pVmxMennD+KeeGCVZFUY60us8/AaIRAmfms1519 8yiYHvZs+GjJB4aHQ/3GbtyX5DlQck1n6ZbTxpbrLr3OOakAd3eSzjsKplRCmjdsZAGm wH2ryBW54x3nFSQDq5Zhj+cWcxMm/c3dAqu4XtdpqmTV/s+9fllcsGaR5yBPcL5IIP5i KeUULk5VoPnhNSACPohvaeFdNPhWqEvfFHcBJ0mtCdfRl6gRllVr7x99HUO4ymP4+Eba vVRA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j5si9177409ejq.397.2019.07.25.05.56.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jul 2019 05:56:37 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id D02BCAF05; Thu, 25 Jul 2019 12:56:36 +0000 (UTC) Date: Thu, 25 Jul 2019 14:56:36 +0200 From: Michal Hocko To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-acpi@vger.kernel.org, "Rafael J. Wysocki" , Andrew Morton , Oscar Salvador Subject: Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan_init() Message-ID: <20190725125636.GA3582@dhcp22.suse.cz> References: <20190724143017.12841-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190724143017.12841-1-david@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 24-07-19 16:30:17, David Hildenbrand wrote: > We end up calling __add_memory() without the device hotplug lock held. > (I used a local patch to assert in __add_memory() that the > device_hotplug_lock is held - I might upstream that as well soon) > > [ 26.771684] create_memory_block_devices+0xa4/0x140 > [ 26.772952] add_memory_resource+0xde/0x200 > [ 26.773987] __add_memory+0x6e/0xa0 > [ 26.775161] acpi_memory_device_add+0x149/0x2b0 > [ 26.776263] acpi_bus_attach+0xf1/0x1f0 > [ 26.777247] acpi_bus_attach+0x66/0x1f0 > [ 26.778268] acpi_bus_attach+0x66/0x1f0 > [ 26.779073] acpi_bus_attach+0x66/0x1f0 > [ 26.780143] acpi_bus_scan+0x3e/0x90 > [ 26.780844] acpi_scan_init+0x109/0x257 > [ 26.781638] acpi_init+0x2ab/0x30d > [ 26.782248] do_one_initcall+0x58/0x2cf > [ 26.783181] kernel_init_freeable+0x1bd/0x247 > [ 26.784345] kernel_init+0x5/0xf1 > [ 26.785314] ret_from_fork+0x3a/0x50 > > So perform the locking just like in acpi_device_hotplug(). While playing with the device_hotplug_lock, can we actually document what it is protecting please? I have a bad feeling that we are adding this lock just because some other code path does rather than with a good idea why it is needed. This patch just confirms that. What exactly does the lock protect from here in an early boot stage. > Cc: "Rafael J. Wysocki" > Cc: Len Brown Cc: Andrew Morton > Cc: Oscar Salvador > Cc: Michal Hocko > Signed-off-by: David Hildenbrand > --- > drivers/acpi/scan.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > index 0e28270b0fd8..cbc9d64b48dd 100644 > --- a/drivers/acpi/scan.c > +++ b/drivers/acpi/scan.c > @@ -2204,7 +2204,9 @@ int __init acpi_scan_init(void) > acpi_gpe_apply_masked_gpes(); > acpi_update_all_gpes(); > > + lock_device_hotplug(); > mutex_lock(&acpi_scan_lock); > + > /* > * Enumerate devices in the ACPI namespace. > */ > @@ -2232,6 +2234,7 @@ int __init acpi_scan_init(void) > > out: > mutex_unlock(&acpi_scan_lock); > + unlock_device_hotplug(); > return result; > } > > -- > 2.21.0 -- Michal Hocko SUSE Labs