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 471B8606A339 for ; Thu, 29 Oct 2026 20:53:16 +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=XNLXlqRw Received: by kanga.kvack.org (Postfix) id C18946B05CD; Thu, 29 Oct 2026 16:44:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BEF2D6B05CE; Thu, 29 Oct 2026 16:44:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B065C6B05D5; Thu, 29 Oct 2026 16:44:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8705D6B05CD for ; Thu, 29 Oct 2026 16:44:53 -0400 (EDT) Received: from smtpin19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 17ECC140512 for ; Thu, 29 Oct 2026 20:44:53 +0000 (UTC) X-FDA: 85376842866.19.190599A Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf06.hostedemail.com (Postfix) with ESMTP id 52FD4180003 for ; Thu, 29 Oct 2026 20:44:51 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XNLXlqRw; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.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=1793306691; 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=0u9mqum51kiy34ukMYiOeDJqgQ6PcqJiGIEfUzDte84=; b=aUcnvOpsGMPOTXjUzrF/9MExgncgsflCwk2qap843Q0+sMROpAdbF3n4ZgHXGd4CwACjeq sPkTxOnqPaLrZ5wZm50hBUXVLpcW4eCxwQZriuUAcV8n+DnkcfApVT4Uolyjy41nh0uuGt tzCgJMY4DZVKuZIPooBdD9LCInFTdQo= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XNLXlqRw; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf06.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=1793306691; b=SmIsm+qGu+miR0tgSqPEDCcWmdfKbSQntvbRjYPeoXS66tWv5Kvn2FQEaHPR9HFUvsHePF ghkueK70pYXHIhp1a+Gv6rvncWo/CQNkdc64BTDQwHbIlkjZPlP/jf5iidYyuPor0Q6ymB 4qQeEyn4OVPe+rg1DA8kM8WLAyvAZH4= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id DA33A601EE; Thu, 29 Oct 2026 20:44:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F9CC1F01824; Thu, 29 Oct 2026 20:44:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306690; bh=0u9mqum51kiy34ukMYiOeDJqgQ6PcqJiGIEfUzDte84=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=XNLXlqRwdRH7zOXlHSAyM5r9l+ZsOYydF9IM6c41SfzDtPH1QjYiKg2vebUPxLRhE op9syInbMCIbPK5ag5w28kgrB20oq6dz6kz7zwHtoMeI3sn0MMvrWpam94RFGJgDxP PwuSJ2sDX281xB+sF7JbamBjH+Lt1N+zLFvcykhavgdcPfZcysVtAD4MHmB4sYH6Ln ybtI5TkPw6mEClQrIsXfrvgw+3L5rwnHWTSP6EOAsNIyTGyK5uyY2hbH03ERH5/SzU /29GOoPKsf2oq6PwxEHLGhAGPKt6XxH3qiXXHt/UH7EJc+i1SCplW5JPkQ0WQvlUQC DoaDQWsFpWhEA== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:41 +0100 Subject: [PATCH v2 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: <20261029-fixes_core-v2-46-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@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 , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3065; i=david@kernel.org; h=from:subject:message-id; bh=Be0cEORXL/+FFSLbAGaUCWXPcitw/28TU4MyQxK8Pu4=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer+2KdjtU9mUqD/ObE6nfr6W/WsvPu0X2p7PUp8V1b +oT/Z1XdZSyMIhxMMiKKbIEBd83ePlyXW21Gx8zzBxWJpAhDFycAjCRk6cYGdakdG50VWY+a/9V 8/mJgoV/fRerH9Bh/RdRvUB9CnvUSjuG/24s+zm964Q1rNsURSvOGhmcdnscZ7DUsWr7it/1S89 +5wYA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 52FD4180003 X-Stat-Signature: m3ep17oatrmj3b4h6r4xj4uyy4ip6ee7 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=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793306691-350100 X-HE-Meta: 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 5JAwwXUz Wp666AWPS3ueJGV+2141GJM8GjLk49wvqhAL+MhLEespjKuPxmhq7rGUoiE1S0IQ/sfm9Jve5O5Jclu0rO3zycPa9rRMcGHZxtkONPTZZwq3p3COLPIpkrLKdAEYsT3POKHWnQHup7N6+oPzzHhdv1WwEiKtGqEAyXBQuwNyfgSmejuxFI51MC+hI5ca+RzKWkarru+GQcgwwi8sEGbpV4dAb9/wXT/0eOAvBRZeQw3feK6AUc59vhFK7J6kX1078AiyD5N58sJOvioQfym7gzo32AZCI/xDhK0KpM3HsM10Dlfq3vnMDQCmUyrEjCSgthhsvdL0jF5LH0qpknEsa0C+QKxDx1Poe69Hei7MSo/xjvkmxEOtqMvIQTPUhTSCWFju1Hkhe6ZhMiBCDOywT4mx/T0u3Li/MTtEwneaHsVi/ZJD3h138uor2NpfQABjhn2pwHFker7OJFBl9FAwIt8pzuRJEpVyK5yRh 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) 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 25e121851b58..8eda313cf619 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