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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 2CF01C433FF for ; Wed, 31 Jul 2019 14:17:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2FB820449 for ; Wed, 31 Jul 2019 14:17:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564582627; bh=8jdEF0UH5jaMsV1Zdp3Wv7KaJzAst2tDDCuDRenrLro=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=is09g6mAc+fwXWX1FxQmyXpupmOfbmZfvDKXIzIr464F+7JREDbXvzRDt4BkKOVwY WwQUahJXTviTOBZkuF2ICbfwIouYXjDQ4TMOzSFm5sEu8Q1WmF+Gr911fnkZcebxJo w4xb1JrsUdqgGEcGWp6MY/wXS6Ds3dx4K8sJ6jNs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727506AbfGaORG (ORCPT ); Wed, 31 Jul 2019 10:17:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:50484 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726308AbfGaORG (ORCPT ); Wed, 31 Jul 2019 10:17:06 -0400 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 23B6BAE5C; Wed, 31 Jul 2019 14:17:05 +0000 (UTC) Date: Wed, 31 Jul 2019 16:17:04 +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" , Oscar Salvador , Andrew Morton Subject: Re: [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock Message-ID: <20190731141704.GW9330@dhcp22.suse.cz> References: <20190731135306.31524-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190731135306.31524-1-david@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Wed 31-07-19 15:53:06, David Hildenbrand wrote: > Let's document why the lock is not needed in acpi_scan_init(), right now > this is not really obvious. > > Cc: Rafael J. Wysocki > Cc: Michal Hocko > Cc: Oscar Salvador > Cc: Andrew Morton > Signed-off-by: David Hildenbrand Acked-by: Michal Hocko Thanks! > --- > > @Andrew, can you drop "drivers/acpi/scan.c: acquire device_hotplug_lock in > acpi_scan_init()" and add this patch instead? Thanks > > --- > drivers/acpi/scan.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > index 0e28270b0fd8..8444af6cd514 100644 > --- a/drivers/acpi/scan.c > +++ b/drivers/acpi/scan.c > @@ -2204,6 +2204,12 @@ int __init acpi_scan_init(void) > acpi_gpe_apply_masked_gpes(); > acpi_update_all_gpes(); > > + /* > + * Although we call__add_memory() that is documented to require the > + * device_hotplug_lock, it is not necessary here because this is an > + * early code when userspace or any other code path cannot trigger > + * hotplug/hotunplug operations. > + */ > mutex_lock(&acpi_scan_lock); > /* > * Enumerate devices in the ACPI namespace. > -- > 2.21.0 -- Michal Hocko SUSE Labs