From nobody Fri Dec 19 16:01:38 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB5B1C433FE for ; Sat, 22 Oct 2022 08:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234774AbiJVIrR (ORCPT ); Sat, 22 Oct 2022 04:47:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235138AbiJVIom (ORCPT ); Sat, 22 Oct 2022 04:44:42 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDD8B2E9E04; Sat, 22 Oct 2022 01:08:35 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 36EEEB82DFA; Sat, 22 Oct 2022 08:00:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C658C433D6; Sat, 22 Oct 2022 08:00:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666425610; bh=CM0lsX2xNuDhqw6knoqtt6uLkfZ93Q02MCIk5faF5dE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xQdN2hfdKHwuS2aAQ6flNLsTnWE1TX3KJOfdG7aS8m44B5pLou48sqP/5nS5rIzVK ilmcKhrcYgr16nvJUWf0YAlI7cxX21lH+KsLjVxDp6JOVkWe0A8SfZpUW7ABqKENMG pRfMINDxELonqmFgmnDR090A3vuY3ZLXtGVMnSt4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nico Pache , Daniel Bristot de Oliveira , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 5.19 527/717] tracing/osnoise: Fix possible recursive locking in stop_per_cpu_kthreads Date: Sat, 22 Oct 2022 09:26:46 +0200 Message-Id: <20221022072521.625085247@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221022072415.034382448@linuxfoundation.org> References: <20221022072415.034382448@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Nico Pache [ Upstream commit 99ee9317a1305cd5626736785c8cb38b0e47686c ] There is a recursive lock on the cpu_hotplug_lock. In kernel/trace/trace_osnoise.c:_per_cpu_kthreads: - start_per_cpu_kthreads calls cpus_read_lock() and if start_kthreads returns a error it will call stop_per_cpu_kthreads. - stop_per_cpu_kthreads then calls cpus_read_lock() again causing deadlock. Fix this by calling cpus_read_unlock() before calling stop_per_cpu_kthreads. This behavior can also be seen in commit f46b16520a08 ("trace/hwlat: Implement the per-cpu mode"). This error was noticed during the LTP ftrace-stress-test: WARNING: possible recursive locking detected Acked-by: Daniel Bristot de Oliveira -------------------------------------------- sh/275006 is trying to acquire lock: ffffffffb02f5400 (cpu_hotplug_lock){++++}-{0:0}, at: stop_per_cpu_kthreads but task is already holding lock: ffffffffb02f5400 (cpu_hotplug_lock){++++}-{0:0}, at: start_per_cpu_kthreads other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(cpu_hotplug_lock); lock(cpu_hotplug_lock); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by sh/275006: #0: ffff8881023f0470 (sb_writers#24){.+.+}-{0:0}, at: ksys_write #1: ffffffffb084f430 (trace_types_lock){+.+.}-{3:3}, at: rb_simple_write #2: ffffffffb02f5400 (cpu_hotplug_lock){++++}-{0:0}, at: start_per_cpu_kth= reads Link: https://lkml.kernel.org/r/20220919144932.3064014-1-npache@redhat.com Fixes: c8895e271f79 ("trace/osnoise: Support hotplug operations") Signed-off-by: Nico Pache Acked-by: Daniel Bristot de Oliveira Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/trace_osnoise.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 313439920a8c..78d536d3ff3d 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -1786,8 +1786,9 @@ static int start_per_cpu_kthreads(void) for_each_cpu(cpu, current_mask) { retval =3D start_kthread(cpu); if (retval) { + cpus_read_unlock(); stop_per_cpu_kthreads(); - break; + return retval; } } =20 --=20 2.35.1