From mboxrd@z Thu Jan 1 00:00:00 1970 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 C70C4C4167B for ; Mon, 27 Nov 2023 07:14:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232460AbjK0HOL (ORCPT ); Mon, 27 Nov 2023 02:14:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232375AbjK0HOJ (ORCPT ); Mon, 27 Nov 2023 02:14:09 -0500 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6706FC3; Sun, 26 Nov 2023 23:14:15 -0800 (PST) Received: from pps.filterd (m0279871.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3AR6wq3L002122; Mon, 27 Nov 2023 07:14:03 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=qcppdkim1; bh=yWRDbKWjbkyTrtsBTWPleY96jb2ymjXC2VRjwvDOW7w=; b=e4IpqhlnxoWrjGaf2peVS5k1F0aPBRI3MwQalI8QZQYFF0VkfvlljdPWyz6rAYsHDBwq TS7x6wyrF2/3Mj+fX21sbgi2zs+SpVBBcwvhbAi4aSbT5+4zycO+mU1Gu5I0bHC4wbIB p+kzNaMTmyZC6L+pjvff/uf8pjaY7GWBehxoJczUzPNf1lFz3FfrN8vATu37hiGMqilt 6tP1hQ4xgMf5mLgWcUsbnt3n3JL5SYQjdADMblY6vbowS6xSP2coPiFlfDi0BFkQsYax 0O4Zyxk4osK60wV+M55OC55NVh548NSF+HSDyWEZao3On7zEq2eDfEhhUPF/Mw0xhH9z fw== Received: from nasanppmta02.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3uk8h8kfjg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 27 Nov 2023 07:14:03 +0000 Received: from nasanex01b.na.qualcomm.com (nasanex01b.na.qualcomm.com [10.46.141.250]) by NASANPPMTA02.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 3AR7DwxR016426 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 27 Nov 2023 07:13:58 GMT Received: from [10.253.15.56] (10.80.80.8) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.40; Sun, 26 Nov 2023 23:13:55 -0800 Message-ID: <639d6008-bdfa-4b6e-b622-e916003ec908@quicinc.com> Date: Mon, 27 Nov 2023 15:13:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/4] bus: mhi: host: Drop chan lock before queuing buffers Content-Language: en-US To: Manivannan Sadhasivam CC: , , , , , References: <1699939661-7385-1-git-send-email-quic_qianyu@quicinc.com> <1699939661-7385-3-git-send-email-quic_qianyu@quicinc.com> <20231124100403.GA4536@thinkpad> From: Qiang Yu In-Reply-To: <20231124100403.GA4536@thinkpad> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: -UL4--dwQ8TrXlyhpAiwRjC-fuIDLUGS X-Proofpoint-GUID: -UL4--dwQ8TrXlyhpAiwRjC-fuIDLUGS X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-27_05,2023-11-22_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 mlxlogscore=754 impostorscore=0 bulkscore=0 phishscore=0 malwarescore=0 mlxscore=0 adultscore=0 clxscore=1015 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311270049 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/24/2023 6:04 PM, Manivannan Sadhasivam wrote: > On Tue, Nov 14, 2023 at 01:27:39PM +0800, Qiang Yu wrote: >> Ensure read and write locks for the channel are not taken in succession by >> dropping the read lock from parse_xfer_event() such that a callback given >> to client can potentially queue buffers and acquire the write lock in that >> process. Any queueing of buffers should be done without channel read lock >> acquired as it can result in multiple locks and a soft lockup. >> > Is this patch trying to fix an existing issue in client drivers or a potential > issue in the future drivers? > > Even if you take care of disabled channels, "mhi_event->lock" acquired during > mhi_mark_stale_events() can cause deadlock, since event lock is already held by > mhi_ev_task(). > > I'd prefer not to open the window unless this patch is fixing a real issue. > > - Mani In [PATCH v4 1/4] bus: mhi: host: Add spinlock to protect WP access when queueing TREs,  we add write_lock_bh(&mhi_chan->lock)/write_unlock_bh(&mhi_chan->lock) in mhi_gen_tre, which may be invoked as part of mhi_queue in client xfer callback, so we have to use read_unlock_bh(&mhi_chan->lock) here to avoid acquiring mhi_chan->lock twice. Sorry for confusing you. Do you think we need to sqush this two patch into one? >> Signed-off-by: Qiang Yu >> --- >> drivers/bus/mhi/host/main.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c >> index 6c6d253..c4215b0 100644 >> --- a/drivers/bus/mhi/host/main.c >> +++ b/drivers/bus/mhi/host/main.c >> @@ -642,6 +642,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl, >> mhi_del_ring_element(mhi_cntrl, tre_ring); >> local_rp = tre_ring->rp; >> >> + read_unlock_bh(&mhi_chan->lock); >> + >> /* notify client */ >> mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result); >> >> @@ -667,6 +669,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl, >> kfree(buf_info->cb_buf); >> } >> } >> + >> + read_lock_bh(&mhi_chan->lock); >> } >> break; >> } /* CC_EOT */ >> -- >> 2.7.4 >> >>