From nobody Sat Oct 18 02:26:13 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 2D801C43217 for ; Wed, 19 Oct 2022 09:35:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233923AbiJSJeB (ORCPT ); Wed, 19 Oct 2022 05:34:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233771AbiJSJ3Y (ORCPT ); Wed, 19 Oct 2022 05:29:24 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2C26C58BE; Wed, 19 Oct 2022 02:12:59 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 2CEC661886; Wed, 19 Oct 2022 09:08:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 405E4C43144; Wed, 19 Oct 2022 09:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666170496; bh=CM0lsX2xNuDhqw6knoqtt6uLkfZ93Q02MCIk5faF5dE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jK84knL91kszEr50fLxA3xwU0z4n7zg4kM9luGiCByChmSXXjsWMmAdjlqFYLhSiQ leeWYjYcx19R3AepVzsLENSzb0igJ8JUsa1li2D/jO4GVGlnjvgSpYQ5Pywdde4a0s Xxgq2ObgCazgC+eYiksLYeSrY8lF6m6nN5CN9n10= 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 6.0 645/862] tracing/osnoise: Fix possible recursive locking in stop_per_cpu_kthreads Date: Wed, 19 Oct 2022 10:32:12 +0200 Message-Id: <20221019083318.425224404@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221019083249.951566199@linuxfoundation.org> References: <20221019083249.951566199@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