From patchwork Tue Sep 24 09:45:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Li X-Patchwork-Id: 13810621 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (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 D1181482D8 for ; Tue, 24 Sep 2024 09:53:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727171634; cv=none; b=U8B6rcjuR2q6MvBHtaJuZwttzeW2bUS7pqETpTD+NOLbx/XYVKldS9HbxSrLSr6AQWhkNmXAg2SMEZBmy4fRBD1oon0V+bFGGbHPb7JXZaM19zY6+TUUi3IyxfTeKpRqk0RXoOfU3vzUH+pHR9/yqioeEVbwg8UERxaYV9wKXrw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727171634; c=relaxed/simple; bh=pHR0UkvKEGYhOkAyV8FTZLacUpWReaRNRwQOAV91g5k=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=lcZf/4A8fNo7kDONPZ3AIEOKdjyA5iql79Uqm5wKMMCSUV1EdXHbnfRvzEJrzHZNKyp5yuv4gyD4upXVRnz8VXoE687hdZgxuYYL7q4gYshEwsrO4wVKPEEygEP3T+MUpunOQWQmz/E0o4VL5k2X2kvhRFWpUUhIAqmuQk/VLSM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.48]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4XCZtX3l51zQrQZ; Tue, 24 Sep 2024 17:53:24 +0800 (CST) Received: from kwepemd100024.china.huawei.com (unknown [7.221.188.41]) by mail.maildlp.com (Postfix) with ESMTPS id DF6AF180087; Tue, 24 Sep 2024 17:53:44 +0800 (CST) Received: from ubuntu-20-04.huawei.com (10.175.103.91) by kwepemd100024.china.huawei.com (7.221.188.41) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 24 Sep 2024 17:53:44 +0800 From: Wei Li To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Daniel Bristot de Oliveira CC: , Subject: [PATCH 5/5] tracing/hwlat: Fix deadlock in cpuhp processing Date: Tue, 24 Sep 2024 17:45:15 +0800 Message-ID: <20240924094515.3561410-6-liwei391@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240924094515.3561410-1-liwei391@huawei.com> References: <20240924094515.3561410-1-liwei391@huawei.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemd100024.china.huawei.com (7.221.188.41) Another "hung task" error was reported during the test, and i figured out the deadlock scenario is as follows: T1 [BP] | T2 [AP] | T3 [hwlatd/1] | T4 work_for_cpu_fn() | cpuhp_thread_fun() | kthread_fn() | hwlat_hotplug_workfn() _cpu_down() | stop_cpu_kthread() | | mutex_lock(&hwlat_data.lock) cpus_write_lock() | kthread_stop(hwlatd/1) | mutex_lock(&hwlat_data.lock) | __cpuhp_kick_ap() | wait_for_completion() | | cpus_read_lock() It constitutes ABBA deadlock indirectly between "cpu_hotplug_lock" and "hwlat_data.lock", make the mutex obtaining in kthread_fn() interruptible to fix this. Fixes: ba998f7d9531 ("trace/hwlat: Support hotplug operations") Signed-off-by: Wei Li --- kernel/trace/trace_hwlat.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index 3bd6071441ad..4c228ccb8a38 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -370,7 +370,8 @@ static int kthread_fn(void *data) get_sample(); local_irq_enable(); - mutex_lock(&hwlat_data.lock); + if (mutex_lock_interruptible(&hwlat_data.lock)) + break; interval = hwlat_data.sample_window - hwlat_data.sample_width; mutex_unlock(&hwlat_data.lock);