From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590425; b=ULM+t/fQC7Ps1d8wPYQcmk/u2lZ52uRDD8QnRYYnZ/2I6AKNA5so4F7IhjsN2+x4GqXl WqEzM2Cgo0wBe4wwGMyMi1XUj66gZnW/coWXWPu4NAmuVHvlHNHCBc3HLpOpxKBHyUxVO OC0jKlq2EMFzsxJvqMKPBrqKORuMfAbs1F+lZb1fJ96t0aHZ37NH9xe4uu4pYTrhdCDCZ 6L2MIUCllMG57vINW0l4ye41kRhO6KCmYVCCnTBMZZYcvyCgAodTjrkE5l+9AQQW/mgxl EphCzapbe0pmOAmo7xib/UBBfC9R82RflVD1cKWWJWFB9Z49t5W2pCzHmM/74ufRoLA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590425; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=7I5ZU+owi40/ByiV4wt9hisJHBeRvhlIIfld81U7rWU=; b=5QOEtS6Q0oe0BMesNaOZyRWlLoHRmSqdanXeWkbKQ97kRABRea/DuLS4ClJ3GyIYiKAW R2WEcFDmslQcCObK1T1f9lxUp2FrWA1NeL6ntnDIgmKSbQIVdYMKEAySCDwtC7rvksY9G lup6xlrn7AoxhkAIgS52MNLR0448ZB7k/wUHE7i/PFU2vaYRa1jKMTam6DupG/FkjSfD3 Ga4w1O0jUltPC1iVoMXfICAuoSOvNGQIeK8hw9TtaHvM7xTcYiBmNSlD20VLzm27iZWwH C7xf/cWFYSIsPbBgXzxRb6SuzgNdh/HuW0Gi7Na4tD8pxi3xxIgJtuDrxSWCtyXrbsg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=WW3nyxFa; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 81DA8606A884; Fri, 13 Nov 2026 17:20:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=WW3nyxFa Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2E6A71F000C4; Fri, 13 Nov 2026 17:20:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590425; bh=7I5ZU+owi40/ByiV4wt9hisJHBeRvhlIIfld81U7rWU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WW3nyxFa/RFekNDQpexhRqLk/etqIoAIAjpZme975+BHbAaVC+pq0nBAYV9hVxekq m+1YUyqEVV+gd3KwzCzHvedyI0Jwy8heJmiYLuLOgw3ZKAV/351r9451iIQKUPwUv6 vH0TO8rfiFNrE1LYJt2YjXqtDwQsnUkb+Z1Ehizo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , "Gregory Price (Meta)" , Muhammad Usama Anjum , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.18 388/686] mm/memory-tiers: unregister empty tiers outside memory_tier_lock Date: Fri, 13 Nov 2026 10:48:41 -0500 Message-ID: <20261113153834.154089883@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand (Arm) [ Upstream commit 500624f28eca441e35f978979ccfb373202fefd3 ] 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 Link: https://patch.msgid.link/20261031-fixes_core-v3-46-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- 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 864811fff4093..fb3d63be1b897 100644 --- a/mm/memory-tiers.c +++ b/mm/memory-tiers.c @@ -561,21 +561,14 @@ 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 @@ -593,14 +586,10 @@ 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) @@ -873,13 +862,21 @@ 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); -- 2.53.0