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[209.132.183.28]) by mx.google.com with ESMTPS id 9si24559017qtm.15.2019.07.31.05.32.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jul 2019 05:32:08 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9348185542; Wed, 31 Jul 2019 12:32:07 +0000 (UTC) Received: from t460s.redhat.com (ovpn-117-240.ams2.redhat.com [10.36.117.240]) by smtp.corp.redhat.com (Postfix) with ESMTP id 792775C1B5; Wed, 31 Jul 2019 12:32:02 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-acpi@vger.kernel.org, David Hildenbrand , "Rafael J . Wysocki" , Michal Hocko , Oscar Salvador , Andrew Morton Subject: [PATCH v1] drivers/acpi/scan.c: Fixup "acquire device_hotplug_lock in acpi_scan_init()" Date: Wed, 31 Jul 2019 14:32:01 +0200 Message-Id: <20190731123201.13893-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 31 Jul 2019 12:32:07 +0000 (UTC) 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: Let's document why we take the lock here. If we're going to overhaul memory hotplug locking, we'll have to touch many places - this comment will help to clairfy why it was added here. Cc: Rafael J. Wysocki Cc: Michal Hocko Cc: Oscar Salvador Cc: Andrew Morton Signed-off-by: David Hildenbrand --- drivers/acpi/scan.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index cbc9d64b48dd..9193f1d46148 100644 --- a/drivers/acpi/scan.c +++ b/drivers/acpi/scan.c @@ -2204,6 +2204,11 @@ int __init acpi_scan_init(void) acpi_gpe_apply_masked_gpes(); acpi_update_all_gpes(); + /* + * We end up calling __add_memory(), which expects the + * device_hotplug_lock to be held. Races with userspace and other + * hotplug activities are not really possible - lock for consistency. + */ lock_device_hotplug(); mutex_lock(&acpi_scan_lock); -- 2.21.0