From patchwork Thu Sep 27 09:25:48 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 10617699 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 98C4814BD for ; Thu, 27 Sep 2018 09:26:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 885FA2AFF0 for ; Thu, 27 Sep 2018 09:26:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7A5A72AFFB; Thu, 27 Sep 2018 09:26:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F201C2AFF0 for ; Thu, 27 Sep 2018 09:26:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 784C88E0004; Thu, 27 Sep 2018 05:26:08 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 70C688E0001; Thu, 27 Sep 2018 05:26:08 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5E5A98E0004; Thu, 27 Sep 2018 05:26:08 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by kanga.kvack.org (Postfix) with ESMTP id 2F97D8E0001 for ; Thu, 27 Sep 2018 05:26:08 -0400 (EDT) Received: by mail-qk1-f199.google.com with SMTP id u86-v6so1924925qku.5 for ; Thu, 27 Sep 2018 02:26:08 -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:from:to:cc :subject:date:message-id; bh=sMu6OYZkDrLMFpe5UH2RIpHJiCnD855ImtivxdscGQY=; b=r0KXTqr8RvP/XOGgGctqES5WK21G8ROKI4qr6wUbNd6ZdVI/eS0szOnhVcOBIp9Pae b/i+UhaTi/wF+juWltL0r7RCdQosJHJdmJNTaDvYtPpvLtVXdUlNsvVtFYrZeZ4V5b6z AnP0aeUDIG5TaTXDT8WfZ4aHfafLcDEUMu0ToDRKBcaYu0JYoSHUDMLgEDoVkShIR3OR ng+0fZVQGl/lZG+EgxI93GTziAvxQoMZTylFZ1ZQEU5n0Qs8ZUGAa9K8Wt/Nba1ZAyRv sYdXUZKjG06u4qGP3JyhxEKniayuKqYe8q+NXYHUTkCWkpB2ejipl+eVgsLa5wheK2tS T5lg== X-Original-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 X-Gm-Message-State: ABuFfoh+pTMkDmLpwgkcM8jAnJX8CKQAPxOro8zlfYtJ/bgOF4ElhoOY v8j0HRzjta0i+0EzNrw5JpzB+FHjU76PIetza5NeLrEfRuE4XRTR9L/24iAwrLalGx8fGTnEp6p 4s3cn6+SMUV3VVDAHrZImstb1en6cb09SLHQpmb10yXDEI1XdjctCHHWdrX1HaMFSUg== X-Received: by 2002:a37:3245:: with SMTP id y66-v6mr7022452qky.205.1538040367946; Thu, 27 Sep 2018 02:26:07 -0700 (PDT) X-Google-Smtp-Source: ACcGV639QIYwFS2aFEjN3Sf+OU2WwXwvu3vkewVphQnFDzmwyudl9A9rKhv3GYwZXjC3KaftjM8E X-Received: by 2002:a37:3245:: with SMTP id y66-v6mr7022433qky.205.1538040367254; Thu, 27 Sep 2018 02:26:07 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1538040367; cv=none; d=google.com; s=arc-20160816; b=OsgqE7FIfwFqaHs8qNEuimr9g+0wqni3sTcZ+0lSwFDGjorrWQZxIADhUeCLh+v0Zd Ah8jGI7V3b+jwKhRsw0d3HFpwpS4d5svAQpJxPLVWRdXVK5qCI0QRT0ZsgUpDe++lou/ +vMI/6YLuaboyIHjYmKSsqNGA1dFlLaJhIXBX2tT7s++WqTBoxBb+t3N3RtH9i5yVvS2 eN3lYXNaB05bt55gue15HU5ZAbLxfjXlnhlsiz6ELQUZj6o4QO+yCTqD0pGTGVxCXpX+ xaKQi3eWpftkC173BV5DTKC+kQbVSA35OOwSzCmx9bIVCUd38d6ka9R7Gr1oN73+pdEa b7fA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:date:subject:cc:to:from; bh=sMu6OYZkDrLMFpe5UH2RIpHJiCnD855ImtivxdscGQY=; b=IRTpBfs2QAbDaCr2nFbpj6kbjz29/0ChTPBWxrSPGfjY7ttTRllL0ue5uTnTSpJxiG BPySfdTiWnRUy+s1jcZC5AMNxaIiKcSS6vK1YBb3svfEPdW/eljrRB5frsA8jYMZur01 JJaMtQfMJ4bKH5KgZ/mVLJVzfuNhV4TrXq7ZoJMlZEAvxTSSRh/YbFHU0LJGGRR1FFl3 DnQVKmNzGPGil7ETm8Q2cB1PneeQ5Ie0YBSUR9CSn0cReHQ4YI6GDK0zDgKwfYqF/Snt WDLVKZhdqhFsUV082EwVxnNg5cQBdbuZD+TqNSuZHGxRkJGZyOJ3eGOWfyCac7ZDCbTO nFSA== ARC-Authentication-Results: i=1; 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 mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id y184-v6si1133131qkb.81.2018.09.27.02.26.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 27 Sep 2018 02:26:07 -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-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.25]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2A8BE30820D8; Thu, 27 Sep 2018 09:26:04 +0000 (UTC) Received: from t460s.redhat.com (ovpn-116-205.ams2.redhat.com [10.36.116.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3D57820154E7; Thu, 27 Sep 2018 09:25:54 +0000 (UTC) From: David Hildenbrand To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, xen-devel@lists.xenproject.org, devel@linuxdriverproject.org, David Hildenbrand , Andrew Morton , Balbir Singh , Benjamin Herrenschmidt , Boris Ostrovsky , Dan Williams , Greg Kroah-Hartman , Haiyang Zhang , Heiko Carstens , John Allen , Jonathan Corbet , Joonsoo Kim , Juergen Gross , Kate Stewart , "K. Y. Srinivasan" , Len Brown , Martin Schwidefsky , Mathieu Malaterre , Michael Ellerman , Michael Neuling , Michal Hocko , Nathan Fontenot , Oscar Salvador , Paul Mackerras , Pavel Tatashin , Pavel Tatashin , Philippe Ombredanne , "Rafael J. Wysocki" , "Rafael J. Wysocki" , Rashmica Gupta , Stephen Hemminger , Thomas Gleixner , Vlastimil Babka , YASUAKI ISHIMATSU Subject: [PATCH v3 0/6] mm: online/offline_pages called w.o. mem_hotplug_lock Date: Thu, 27 Sep 2018 11:25:48 +0200 Message-Id: <20180927092554.13567-1-david@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.25 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Thu, 27 Sep 2018 09:26:06 +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: X-Virus-Scanned: ClamAV using ClamSMTP @Andrew, Only patch #5 changed (see change notes below). Thanks! Reading through the code and studying how mem_hotplug_lock is to be used, I noticed that there are two places where we can end up calling device_online()/device_offline() - online_pages()/offline_pages() without the mem_hotplug_lock. And there are other places where we call device_online()/device_offline() without the device_hotplug_lock. While e.g. echo "online" > /sys/devices/system/memory/memory9/state is fine, e.g. echo 1 > /sys/devices/system/memory/memory9/online Will not take the mem_hotplug_lock. However the device_lock() and device_hotplug_lock. E.g. via memory_probe_store(), we can end up calling add_memory()->online_pages() without the device_hotplug_lock. So we can have concurrent callers in online_pages(). We e.g. touch in online_pages() basically unprotected zone->present_pages then. Looks like there is a longer history to that (see Patch #2 for details), and fixing it to work the way it was intended is not really possible. We would e.g. have to take the mem_hotplug_lock in device/base/core.c, which sounds wrong. Summary: We had a lock inversion on mem_hotplug_lock and device_lock(). More details can be found in patch 3 and patch 6. I propose the general rules (documentation added in patch 6): 1. add_memory/add_memory_resource() must only be called with device_hotplug_lock. 2. remove_memory() must only be called with device_hotplug_lock. This is already documented and holds for all callers. 3. device_online()/device_offline() must only be called with device_hotplug_lock. This is already documented and true for now in core code. Other callers (related to memory hotplug) have to be fixed up. 4. mem_hotplug_lock is taken inside of add_memory/remove_memory/ online_pages/offline_pages. To me, this looks way cleaner than what we have right now (and easier to verify). And looking at the documentation of remove_memory, using lock_device_hotplug also for add_memory() feels natural. v2 -> v3: - Take device_hotplug_lock outside of loop in patch #5 - Added Ack to patch #5 v1 -> v2: - Upstream changes in powerpc/powernv code required modifications to patch #1, #4 and #5. - Minor patch description changes. - Added more locking details in patch #6. - Added rb's RFCv2 -> v1: - Dropped an unnecessary _ref from remove_memory() in patch #1 - Minor patch description fixes. - Added rb's RFC -> RFCv2: - Don't export device_hotplug_lock, provide proper remove_memory/add_memory wrappers. - Split up the patches a bit. - Try to improve powernv memtrace locking - Add some documentation for locking that matches my knowledg David Hildenbrand (6): mm/memory_hotplug: make remove_memory() take the device_hotplug_lock mm/memory_hotplug: make add_memory() take the device_hotplug_lock mm/memory_hotplug: fix online/offline_pages called w.o. mem_hotplug_lock powerpc/powernv: hold device_hotplug_lock when calling device_online() powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages() memory-hotplug.txt: Add some details about locking internals Documentation/memory-hotplug.txt | 42 ++++++++++++- arch/powerpc/platforms/powernv/memtrace.c | 8 ++- .../platforms/pseries/hotplug-memory.c | 8 +-- drivers/acpi/acpi_memhotplug.c | 4 +- drivers/base/memory.c | 22 +++---- drivers/xen/balloon.c | 3 + include/linux/memory_hotplug.h | 4 +- mm/memory_hotplug.c | 59 +++++++++++++++---- 8 files changed, 114 insertions(+), 36 deletions(-)