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 78CE4383C79 for ; Mon, 30 Mar 2026 14:18:10 +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=1774880290; cv=none; b=hfJqdo8dlg+bENWDc/FonjD1CCudGO6qzOJnHvrKQAKkF2wEuNGPCEA6xTW8mBQC+2XF9/j6QX5OnetP9erCyKBSaLdQf2HI9SjlnIvEkLzlaiFEzpuHJluJ44J9AWtbyoVlgfU52xpR5VSvEgzLCeplc1BNVrgc0pUrIBoXUE0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774880290; c=relaxed/simple; bh=yMLL4eZ1IZjR31caId07J3j0PwrZ1v8ccxXM5nCH8+I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jMYEtEez5GUnkGT2ZdkFVpD3RbYdxi6IElWxpiP5aSF4zDu7EnGNhWk4lpLRRvTCiChkq4fjpRLg9+81fsY5NpaqBGMXSk2lHzOYaxA3kVY3Yk6BJ0E3C946S0wt4VVJ1y80KHS/co3Jrw6NJWeDBmjKDjU00GiKKlfsDl3Nj2Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Jj7yf0tv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Jj7yf0tv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43521C19423; Mon, 30 Mar 2026 14:18:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774880290; bh=yMLL4eZ1IZjR31caId07J3j0PwrZ1v8ccxXM5nCH8+I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jj7yf0tvrgUFkv8XRehpW3emfe/5qym9tpAhK0AB5E3pgAnVDSc6Kk+7ivJ4qUwMb QKBAIo2OSZkOBd/9KEeS/f+uCpqyAWYJxwl7r3KPo9HCsIXujDWDp25OZBqvhHzipN nfKlTXiygZ72DySFtV/1teOKUQ0g2dk8fBWAT6t8udarwXH8dTkkvTMVBjmKyuWGdw ORK8abFU0ldCkzS/PQDr2cp9ZGi6BZLbEPqQC+gZwMN8CGGCnrLZVyndpcdEU/z/4H bAgSVbbbpFFJfGZCMAdbbVueAsPSccMhR48pFbuhu3/FfWwUfuFIeoskFxXM8qRJWR cvK/JCchV5vpQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Luo Haiyang , mathieu.desnoyers@efficios.com, zhang.run@zte.com.cn, yang.tao172@zte.com.cn, ran.xiaokai@zte.com.cn, "Masami Hiramatsu (Google)" , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 6.12.y 2/2] tracing: Fix potential deadlock in cpu hotplug with osnoise Date: Mon, 30 Mar 2026 10:18:06 -0400 Message-ID: <20260330141806.817242-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260330141806.817242-1-sashal@kernel.org> References: <2026032952-shredding-snorkel-3530@gregkh> <20260330141806.817242-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Luo Haiyang [ Upstream commit 1f9885732248d22f788e4992c739a98c88ab8a55 ] The following sequence may leads deadlock in cpu hotplug: task1 task2 task3 ----- ----- ----- mutex_lock(&interface_lock) [CPU GOING OFFLINE] cpus_write_lock(); osnoise_cpu_die(); kthread_stop(task3); wait_for_completion(); osnoise_sleep(); mutex_lock(&interface_lock); cpus_read_lock(); [DEAD LOCK] Fix by swap the order of cpus_read_lock() and mutex_lock(&interface_lock). Cc: stable@vger.kernel.org Cc: Cc: Cc: Cc: Fixes: bce29ac9ce0bb ("trace: Add osnoise tracer") Link: https://patch.msgid.link/20260326141953414bVSj33dAYktqp9Oiyizq8@zte.com.cn Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Luo Haiyang Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/trace_osnoise.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 412ca1efa956e..7d96be13367f3 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -2104,8 +2104,8 @@ static void osnoise_hotplug_workfn(struct work_struct *dummy) if (!osnoise_has_registered_instances()) return; - guard(mutex)(&interface_lock); guard(cpus_read_lock)(); + guard(mutex)(&interface_lock); if (!cpu_online(cpu)) return; @@ -2268,11 +2268,11 @@ static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf, if (running) stop_per_cpu_kthreads(); - mutex_lock(&interface_lock); /* * avoid CPU hotplug operations that might read options. */ cpus_read_lock(); + mutex_lock(&interface_lock); retval = cnt; @@ -2288,8 +2288,8 @@ static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf, clear_bit(option, &osnoise_options); } - cpus_read_unlock(); mutex_unlock(&interface_lock); + cpus_read_unlock(); if (running) start_per_cpu_kthreads(); @@ -2375,16 +2375,16 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count, if (running) stop_per_cpu_kthreads(); - mutex_lock(&interface_lock); /* * osnoise_cpumask is read by CPU hotplug operations. */ cpus_read_lock(); + mutex_lock(&interface_lock); cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new); - cpus_read_unlock(); mutex_unlock(&interface_lock); + cpus_read_unlock(); if (running) start_per_cpu_kthreads(); -- 2.53.0