From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 76CCE606A31C for ; Sat, 31 Oct 2026 09:52:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=WDaRfZV8 Received: by kanga.kvack.org (Postfix) id 8BF106B05F8; Sat, 31 Oct 2026 05:52:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 86EA76B05F9; Sat, 31 Oct 2026 05:52:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 75D4C6B05FA; Sat, 31 Oct 2026 05:52:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 4B2AE6B05F8 for ; Sat, 31 Oct 2026 05:52:15 -0400 (EDT) Received: from smtpin23.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id C57EAC095A for ; Sat, 31 Oct 2026 09:52:14 +0000 (UTC) X-FDA: 85382455788.23.9301A2E Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf07.hostedemail.com (Postfix) with ESMTP id 1AA5D40003 for ; Sat, 31 Oct 2026 09:52:12 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WDaRfZV8; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793440333; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=LXWsGGAuGYMpNthZzj7j0qIEhHCnCLdw4tDv3Dde7tU=; b=4o6g8LIegmehUXZuzXT4rZqUC0C4wKdyljcGuGwvHD7yyG9ZBTReEnvcbuL9qol28Gz0ju WCXu1YYW3L6vQ+cm10nb2zT+e7thIagowdAgRsYcQNYIF/POhbYfKT6bqHvbI+uWGeQPIX KnMTFMPzFt2AeStA3hyk3xEY4rbNEkQ= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WDaRfZV8; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793440333; b=FXzbsAmO1o2OMl3ENk0Ep4OrbDhXbPzJkhhhXQBaJMFdWWl066AQ0R+xxnjvrpDfi1h0NX WkKq0dbuiWJZNhx46t/pwZIXbqIAMdewhOfnCAfvHoLANApx/qJCAmIyrP++gIEx0go3Mz pOYWkB0hPLrWHGwbiP0AEtI36g/ZrXg= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id AE00F600C8; Sat, 31 Oct 2026 09:52:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99D3F1F00919; Sat, 31 Oct 2026 09:51:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793440332; bh=LXWsGGAuGYMpNthZzj7j0qIEhHCnCLdw4tDv3Dde7tU=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=WDaRfZV8lrdSHWo2bJPjhRAvbOAWGSBSNWe8J3upHnl+8qcyY3Ce8G7dfUa1DjNu8 H8f+FSaHVuGPPNLccj7ytAj3BCbt3FdYbeSSKQF/QvfRjblvOsaNaGnbw9hLcvhcsJ dDRBr8BfUwDlVj32RVLLIYvP7S3lEAMUk4hAgnS3bHgLHai9rCoFXH1JhD19+t2mMl n7zx2EBIckhQ3seuwiWQtQn9Jl0jqIz4d6PcM9b+vRYVjFs35sap3cB26D91h0RaDe MOMYNkE9tGqvEbueSr3By16YiV7Ok4fX4v3f6g5/bvzabRudn/+qA5QxL3Z0bM3mj6 nFye94PFipthw== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:40:15 +0100 Subject: [PATCH v3 46/47] mm/memory-tiers: unregister empty tiers outside memory_tier_lock X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-46-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Josef Bacik , Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3122; i=david@kernel.org; h=from:subject:message-id; bh=4kChVYvvx74BRlmNy9r2/KDpSY0XvvEjaE2NRYfL7Rw=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebs9+99iyuX3mtNxzRav077QJloZ+YyoR6Cgy2vp4d YX/5CM6HaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAEzk4SaGf/ZLKmUk1xgsDAxl Pc3A+6Vf/4kPc5PbSzOWCXdu2uiXVTAyrOyZI/RJ5uh8YRfxXwU8K8t/sD5yzZZddPjK5FOzcxM mMQAA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Queue-Id: 1AA5D40003 X-Rspam-User: X-Stat-Signature: zjtmexmp1cy6uqct7sjc3q7jm8anghhj X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam03 X-HE-Tag: 1793440332-777879 X-HE-Meta: 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 er+L4Nn9 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 When offlining a node's last memory empties its tier, clear_node_memory_tier() calls device_unregister() while holding memory_tier_lock. A concurrent sysfs read can hold a kernfs active reference and block in nodelist_show() on that mutex. device_unregister() then waits in kernfs_drain() for the read to finish and release its active reference, while the reader waits for the offlining task to release the mutex. Return the node's former tier from clear_node_memory_tier(), making the helper more similar to set_node_memory_tier(), which also returns a memory_tier pointer. Let the caller unlink an empty tier under memory_tier_lock before rebuilding demotion targets, then unregister its device after dropping the lock. Fixes: 9832fb87834e ("mm/demotion: expose memory tier details via sysfs") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Gregory Price (Meta) Tested-by: Muhammad Usama Anjum Signed-off-by: David Hildenbrand (Arm) --- mm/memory-tiers.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-) diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c index 25e121851b586..8eda313cf6192 100644 --- a/mm/memory-tiers.c +++ b/mm/memory-tiers.c @@ -572,21 +572,14 @@ static struct memory_tier *set_node_memory_tier(int node) return memtier; } -static void destroy_memory_tier(struct memory_tier *memtier) +static struct memory_tier *clear_node_memory_tier(int node) { - list_del(&memtier->list); - device_unregister(&memtier->dev); -} - -static bool clear_node_memory_tier(int node) -{ - bool cleared = false; pg_data_t *pgdat; struct memory_tier *memtier; pgdat = NODE_DATA(node); if (!pgdat) - return false; + return NULL; /* * Make sure that anybody looking at NODE_DATA who finds @@ -604,14 +597,10 @@ static bool clear_node_memory_tier(int node) synchronize_rcu(); memtype = node_memory_types[node].memtype; node_clear(node, memtype->nodes); - if (nodes_empty(memtype->nodes)) { + if (nodes_empty(memtype->nodes)) list_del_init(&memtype->tier_sibling); - if (list_empty(&memtier->memory_types)) - destroy_memory_tier(memtier); - } - cleared = true; } - return cleared; + return memtier; } static void release_memtype(struct kref *kref) @@ -884,13 +873,21 @@ static int __meminit memtier_hotplug_callback(struct notifier_block *self, { struct memory_tier *memtier; struct node_notify *nn = _arg; + bool empty = false; switch (action) { case NODE_REMOVED_LAST_MEMORY: mutex_lock(&memory_tier_lock); - if (clear_node_memory_tier(nn->nid)) + memtier = clear_node_memory_tier(nn->nid); + if (memtier) { + empty = list_empty(&memtier->memory_types); + if (empty) + list_del(&memtier->list); establish_demotion_targets(); + } mutex_unlock(&memory_tier_lock); + if (empty) + device_unregister(&memtier->dev); break; case NODE_ADDED_FIRST_MEMORY: mutex_lock(&memory_tier_lock); -- 2.43.0