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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 0E842C4321D for ; Tue, 21 Aug 2018 10:44:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B46C52170E for ; Tue, 21 Aug 2018 10:44:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B46C52170E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1727358AbeHUOE1 (ORCPT ); Tue, 21 Aug 2018 10:04:27 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44736 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726859AbeHUOE0 (ORCPT ); Tue, 21 Aug 2018 10:04:26 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D872D8068B0B; Tue, 21 Aug 2018 10:44:46 +0000 (UTC) Received: from t460s.redhat.com (ovpn-117-96.ams2.redhat.com [10.36.117.96]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2AD0F9463B; Tue, 21 Aug 2018 10:44:40 +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 , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , "Rafael J. Wysocki" , Len Brown , Greg Kroah-Hartman , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Martin Schwidefsky , Heiko Carstens , Boris Ostrovsky , Juergen Gross , Rashmica Gupta , Michael Neuling , Balbir Singh , Kate Stewart , Thomas Gleixner , Philippe Ombredanne , Andrew Morton , Michal Hocko , Pavel Tatashin , Vlastimil Babka , Dan Williams , Oscar Salvador , YASUAKI ISHIMATSU , Mathieu Malaterre Subject: [PATCH RFCv2 3/6] mm/memory_hotplug: fix online/offline_pages called w.o. mem_hotplug_lock Date: Tue, 21 Aug 2018 12:44:15 +0200 Message-Id: <20180821104418.12710-4-david@redhat.com> In-Reply-To: <20180821104418.12710-1-david@redhat.com> References: <20180821104418.12710-1-david@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Tue, 21 Aug 2018 10:44:47 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Tue, 21 Aug 2018 10:44:47 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'david@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There seem to be some problems as result of 30467e0b3be ("mm, hotplug: fix concurrent memory hot-add deadlock"), which tried to fix a possible lock inversion reported and discussed in [1] due to the two locks a) device_lock() b) mem_hotplug_lock While add_memory() first takes b), followed by a) during bus_probe_device(), onlining of memory from user space first took b), followed by a), exposing a possible deadlock. In [1], and it was decided to not make use of device_hotplug_lock, but rather to enforce a locking order. The problems I spotted related to this: 1. Memory block device attributes: While .state first calls mem_hotplug_begin() and the calls device_online() - which takes device_lock() - .online does no longer call mem_hotplug_begin(), so effectively calls online_pages() without mem_hotplug_lock. 2. device_online() should be called under device_hotplug_lock, however onlining memory during add_memory() does not take care of that. In addition, I think there is also something wrong about the locking in 3. arch/powerpc/platforms/powernv/memtrace.c calls offline_pages() without locks. This was introduced after 30467e0b3be. And skimming over the code, I assume it could need some more care in regards to locking (e.g. device_online() called without device_hotplug_lock - but I'll not touch that for now). Now that we hold the device_hotplug_lock when - adding memory (e.g. via add_memory()/add_memory_resource()) - removing memory (e.g. via remove_memory()) - device_online()/device_offline() We can move mem_hotplug_lock usage back into online_pages()/offline_pages(). Why is mem_hotplug_lock still needed? Essentially to make get_online_mems()/put_online_mems() be very fast (relying on device_hotplug_lock would be very slow), and to serialize against addition of memory that does not create memory block devices (hmm). [1] http://driverdev.linuxdriverproject.org/pipermail/ driverdev-devel/ 2015-February/065324.html This patch is partly based on a patch by Vitaly Kuznetsov. Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: "Rafael J. Wysocki" Cc: Len Brown Cc: Greg Kroah-Hartman Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Stephen Hemminger Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Boris Ostrovsky Cc: Juergen Gross Cc: Rashmica Gupta Cc: Michael Neuling Cc: Balbir Singh Cc: Kate Stewart Cc: Thomas Gleixner Cc: Philippe Ombredanne Cc: Andrew Morton Cc: Michal Hocko Cc: Pavel Tatashin Cc: Vlastimil Babka Cc: Dan Williams Cc: Oscar Salvador Cc: YASUAKI ISHIMATSU Cc: Mathieu Malaterre Signed-off-by: David Hildenbrand --- drivers/base/memory.c | 13 +------------ mm/memory_hotplug.c | 28 ++++++++++++++++++++-------- 2 files changed, 21 insertions(+), 20 deletions(-) diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 5b0375be7f65..04be13539eb8 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -228,7 +228,6 @@ static bool pages_correctly_probed(unsigned long start_pfn) /* * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is * OK to have direct references to sparsemem variables in here. - * Must already be protected by mem_hotplug_begin(). */ static int memory_block_action(unsigned long phys_index, unsigned long action, int online_type) @@ -294,7 +293,6 @@ static int memory_subsys_online(struct device *dev) if (mem->online_type < 0) mem->online_type = MMOP_ONLINE_KEEP; - /* Already under protection of mem_hotplug_begin() */ ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE); /* clear online_type */ @@ -341,19 +339,11 @@ store_mem_state(struct device *dev, goto err; } - /* - * Memory hotplug needs to hold mem_hotplug_begin() for probe to find - * the correct memory block to online before doing device_online(dev), - * which will take dev->mutex. Take the lock early to prevent an - * inversion, memory_subsys_online() callbacks will be implemented by - * assuming it's already protected. - */ - mem_hotplug_begin(); - switch (online_type) { case MMOP_ONLINE_KERNEL: case MMOP_ONLINE_MOVABLE: case MMOP_ONLINE_KEEP: + /* mem->online_type is protected by device_hotplug_lock */ mem->online_type = online_type; ret = device_online(&mem->dev); break; @@ -364,7 +354,6 @@ store_mem_state(struct device *dev, ret = -EINVAL; /* should never happen */ } - mem_hotplug_done(); err: unlock_device_hotplug(); diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index e2b5c751e3ea..a2c6c87d83f3 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -881,7 +881,6 @@ static struct zone * __meminit move_pfn_range(int online_type, int nid, return zone; } -/* Must be protected by mem_hotplug_begin() or a device_lock */ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type) { unsigned long flags; @@ -893,6 +892,8 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ struct memory_notify arg; struct memory_block *mem; + mem_hotplug_begin(); + /* * We can't use pfn_to_nid() because nid might be stored in struct page * which is not yet initialized. Instead, we find nid from memory block. @@ -957,6 +958,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ if (onlined_pages) memory_notify(MEM_ONLINE, &arg); + mem_hotplug_done(); return 0; failed_addition: @@ -964,6 +966,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ (unsigned long long) pfn << PAGE_SHIFT, (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1); memory_notify(MEM_CANCEL_ONLINE, &arg); + mem_hotplug_done(); return ret; } #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */ @@ -1168,20 +1171,20 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online) /* create new memmap entry */ firmware_map_add_hotplug(start, start + size, "System RAM"); + /* device_online() will take the lock when calling online_pages() */ + mem_hotplug_done(); + /* online pages if requested */ if (online) walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL, online_memory_block); - goto out; - + return ret; error: /* rollback pgdat allocation and others */ if (new_node) rollback_node_hotadd(nid); memblock_remove(start, size); - -out: mem_hotplug_done(); return ret; } @@ -1621,10 +1624,16 @@ static int __ref __offline_pages(unsigned long start_pfn, return -EINVAL; if (!IS_ALIGNED(end_pfn, pageblock_nr_pages)) return -EINVAL; + + mem_hotplug_begin(); + /* This makes hotplug much easier...and readable. we assume this for now. .*/ - if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end)) + if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, + &valid_end)) { + mem_hotplug_done(); return -EINVAL; + } zone = page_zone(pfn_to_page(valid_start)); node = zone_to_nid(zone); @@ -1633,8 +1642,10 @@ static int __ref __offline_pages(unsigned long start_pfn, /* set above range as isolated */ ret = start_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE, true); - if (ret) + if (ret) { + mem_hotplug_done(); return ret; + } arg.start_pfn = start_pfn; arg.nr_pages = nr_pages; @@ -1705,6 +1716,7 @@ static int __ref __offline_pages(unsigned long start_pfn, writeback_set_ratelimit(); memory_notify(MEM_OFFLINE, &arg); + mem_hotplug_done(); return 0; failed_removal: @@ -1714,10 +1726,10 @@ static int __ref __offline_pages(unsigned long start_pfn, memory_notify(MEM_CANCEL_OFFLINE, &arg); /* pushback to free area */ undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); + mem_hotplug_done(); return ret; } -/* Must be protected by mem_hotplug_begin() or a device_lock */ int offline_pages(unsigned long start_pfn, unsigned long nr_pages) { return __offline_pages(start_pfn, start_pfn + nr_pages); -- 2.17.1