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 85DF0350D5D; Tue, 26 Aug 2025 14:03:20 +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=1756217000; cv=none; b=BiAVED3IRLLsM+2AdOCL8vqNQ7zJJm9vbirVvqrd8IUVdMtYnTmfIPHbn7ZZIigcnUZcn9I6+A+9ZlLnIXHSHH5WhAxJKieRZgSbNPRcPd7TixIsbYISiSlYZqhTLNMoyPrG7l584S2hwB1M+OBvoNkaWnzH6x5JrRB2KEtiqrE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756217000; c=relaxed/simple; bh=tUh0H3/5w1+JSNUlL4MS3Xuep+vgn2srVcRXBDcygvo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JFhQxpnwVevCLGKLR4+iL/+QgAGGmAWCQ7KkGAZ2siw6PGenrSMboLevDQ2gvTR47k+95V0mwxt+9rFBxnsUQiSH8RTIbJl2TvK5QIPMsMnnvfUxBksW2L2hGy8OLT/qdZsnOPPxZsRGfXoYY+zeVNDLWpxO/GMat9Dm2mXqWTk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ng/R4Vep; 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="ng/R4Vep" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA2B1C4CEF1; Tue, 26 Aug 2025 14:03:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756217000; bh=tUh0H3/5w1+JSNUlL4MS3Xuep+vgn2srVcRXBDcygvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ng/R4VepVZMWS+JtZ0S2tq4AK1INhZRGFoR9ProJDH69spXnFshgGB+QIh3XG8RSM dgWUAqRqHdg3unaosuhByJRMrc/UqzkDZHkJUX1cxt+OT+96rmjRAg6dVFk5k4cumL pH3vIB+n04ILS958tg8f7V9ayWI8g8k41w5U3PXs= 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 5.15 621/644] cgroup/cpuset: Use static_branch_enable_cpuslocked() on cpusets_insane_config_key Date: Tue, 26 Aug 2025 13:11:52 +0200 Message-ID: <20250826111001.945123474@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110946.507083938@linuxfoundation.org> References: <20250826110946.507083938@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 5.15-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 b40f86a3f605..78c499021768 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -408,7 +408,7 @@ 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