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 566393D8917 for ; Mon, 30 Mar 2026 14:25:51 +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=1774880751; cv=none; b=O2X3RxS7klQKRF5pAlOztjnR9a/1B8k4ukiWnfYDtFJ+B0BoN0p218q09YAY7ZJNqxMMpeu0Fdw4QDf38JpBbhGNn9M261qDCHLL3284p76uaI0yhkHhnjwsiNbNseZWY4mGPFcRkDe5K5HQO+ysuU+hwe8V0ci75QAUvXuGJ8w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774880751; c=relaxed/simple; bh=fWjhQa2IJLuzdtvDtlP6TpvaKY3fQ/5IDVkU5xWhPm0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HFflCYgV7Bswsw7ukRs7xVboL5erf38Q6pZeXyDQvSSaomPNctCTpJFY7jz4rPoQng7NjfaPYSu3IAYMHAi2sK/gkLAi6UdVDqX/zaXN0HiZ6G9QnUsaQ1EDHDAJGvUyMzHMKQ8XdNOHG6DKc/97WzVQAz7mU/hflnZkU+EGJCI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KbL6bOob; 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="KbL6bOob" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08EDAC2BCB2; Mon, 30 Mar 2026 14:25:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774880750; bh=fWjhQa2IJLuzdtvDtlP6TpvaKY3fQ/5IDVkU5xWhPm0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KbL6bOobLWHS9YqhPgcvL7gtt+rfzxMX1D0ZCdgJwPvPmjAX4b2Fzfa9/24W0j0Gq ZlBEStfqIRq1tV3ASn3JWRjTfutVc86kv2q/hFVGApFDSXdN2J6+tu7NTWWCOP0Ppc WI7BGuBrl+X2GoOMlHsA86IXIOatfO3mGWjYeSTqsfiGnVhryUa08fxBlLSX5UDdf+ bmCcSX5z10jRwSIRR+074pBtqf+SaaeiSOnZq8MpG24Xch2Xz/YstZoIUeV3k12ygA H9vnPXjy96Sv+S8hQJ+ZBOMjZx0BkIsknN2Pnz3TCDemkuEn+8xgyOHGV0n3CV+U3Z NGdHcx8Kk/3lA== 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 6.6.y 2/2] tracing: Fix potential deadlock in cpu hotplug with osnoise Date: Mon, 30 Mar 2026 10:25:47 -0400 Message-ID: <20260330142547.819699-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260330142547.819699-1-sashal@kernel.org> References: <2026032953-garnet-dropout-ed0f@gregkh> <20260330142547.819699-1-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 6bf8d18a15b7c..3b039374c993e 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