From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 097D02798ED; Tue, 26 Aug 2025 11:46:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756208809; cv=none; b=XyAhvnsYuwZ7aNn+8Ubiu15mMzCSyQFsv+mNeUy0GSzB/f6xEs8PA2nUiteFuci17E6cq5iCediPRRdF0VCZFcsdtvclw1q72MSglPGNJ2Jv8R4DTtEUezBEDMwJ5mpRGwv6790a0i6b1oX6siZFD5KIXBZ6y23OK9tnQ+l4FII= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756208809; c=relaxed/simple; bh=kJO6/D9A+KNizT0lZugbC0KonxmFSo3+Pm76nvABGrw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CmUSfWKwuRKVQrUefILLWxxj5eQh3M8vwhsD6GW/fOsrQzgOt1VFG1+ZitqRJxTNh8IPyq6vukL1AIUnBWnTSPzyT9PBc//D9YK6pu2zS+Am0IQy4TgK/HBGewVPa+ORhu7MH3vvn+tMp5/Mi7bqkUEWL1A4SwAfa2MhROEdQnQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TMNeVJXF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="TMNeVJXF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FE52C4CEF1; Tue, 26 Aug 2025 11:46:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756208808; bh=kJO6/D9A+KNizT0lZugbC0KonxmFSo3+Pm76nvABGrw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TMNeVJXFHyabg6xBdPv9KWnWn0hPzGa7awBklV4lEnaunrEAGpPXkI9+66YzDp+/M 4lJb1xYlig5IkhVlfR5q6qJk0dG/UzjldbbqjhVyqv+SxryCO69avsW4ZjFXGSBb0O AEQrD+0g97uhRmvhssvNHN+0fu36MiEy/eZcHLWA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Waiman Long , Juri Lelli , Tejun Heo , Sasha Levin Subject: [PATCH 6.12 254/322] cgroup/cpuset: Use static_branch_enable_cpuslocked() on cpusets_insane_config_key Date: Tue, 26 Aug 2025 13:11:09 +0200 Message-ID: <20250826110922.208172216@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110915.169062587@linuxfoundation.org> References: <20250826110915.169062587@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Waiman Long [ Upstream commit 65f97cc81b0adc5f49cf6cff5d874be0058e3f41 ] The following lockdep splat was observed. [ 812.359086] ============================================ [ 812.359089] WARNING: possible recursive locking detected [ 812.359097] -------------------------------------------- [ 812.359100] runtest.sh/30042 is trying to acquire lock: [ 812.359105] ffffffffa7f27420 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_enable+0xe/0x20 [ 812.359131] [ 812.359131] but task is already holding lock: [ 812.359134] ffffffffa7f27420 (cpu_hotplug_lock){++++}-{0:0}, at: cpuset_write_resmask+0x98/0xa70 : [ 812.359267] Call Trace: [ 812.359272] [ 812.359367] cpus_read_lock+0x3c/0xe0 [ 812.359382] static_key_enable+0xe/0x20 [ 812.359389] check_insane_mems_config.part.0+0x11/0x30 [ 812.359398] cpuset_write_resmask+0x9f2/0xa70 [ 812.359411] cgroup_file_write+0x1c7/0x660 [ 812.359467] kernfs_fop_write_iter+0x358/0x530 [ 812.359479] vfs_write+0xabe/0x1250 [ 812.359529] ksys_write+0xf9/0x1d0 [ 812.359558] do_syscall_64+0x5f/0xe0 Since commit d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock order"), the ordering of cpu hotplug lock and cpuset_mutex had been reversed. That patch correctly used the cpuslocked version of the static branch API to enable cpusets_pre_enable_key and cpusets_enabled_key, but it didn't do the same for cpusets_insane_config_key. The cpusets_insane_config_key can be enabled in the check_insane_mems_config() which is called from update_nodemask() or cpuset_hotplug_update_tasks() with both cpu hotplug lock and cpuset_mutex held. Deadlock can happen with a pending hotplug event that tries to acquire the cpu hotplug write lock which will block further cpus_read_lock() attempt from check_insane_mems_config(). Fix that by switching to use static_branch_enable_cpuslocked(). Fixes: d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock order") Signed-off-by: Waiman Long Reviewed-by: Juri Lelli Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- kernel/cgroup/cpuset.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index d1fb4bfbbd4c..af5dc30bfe4b 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -267,7 +267,7 @@ static inline void check_insane_mems_config(nodemask_t *nodes) { if (!cpusets_insane_config() && movable_only_nodes(nodes)) { - static_branch_enable(&cpusets_insane_config_key); + static_branch_enable_cpuslocked(&cpusets_insane_config_key); pr_info("Unsupported (movable nodes only) cpuset configuration detected (nmask=%*pbl)!\n" "Cpuset allocations might fail even with a lot of memory available.\n", nodemask_pr_args(nodes)); -- 2.50.1