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 22D09CE7A8B for ; Mon, 25 Sep 2023 03:10:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230293AbjIYDKo (ORCPT ); Sun, 24 Sep 2023 23:10:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230163AbjIYDKm (ORCPT ); Sun, 24 Sep 2023 23:10:42 -0400 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90BFAA7; Sun, 24 Sep 2023 20:10:32 -0700 (PDT) Received: from pps.filterd (m0279868.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 38P2w9rj014284; Mon, 25 Sep 2023 03:10:21 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=30VHeSyGYzHPzTB3jvCEkL+AUpeDSctcovuhd0vnFV0=; b=f/RjTU52f7b3pYQYD2fEZT2Qvr14BxjU9A3OPNfdYgQ0rSY1eF12HDtIlYXz+x2eM7BM slZtfedheae0MGva7FbcezRLAeAL/Mh+F/ASnUY7Pwc9W4bwqGhKK5mKtlv8/YpQL2Hi 6TwedjDF5MzqieedOZU5v0TUrN4qKxuw8+cB+nhkTVVQJrEz9QuTKHJQtg9fpBh6wLCK osy/EMZpSlP1LWLl5Vugf8euA/Er2xKkHvH4QfblZuq5e/dGAYSy4YxjOq1TGcnQ7N8C /uMQyPthOrxx9Bw2JZwyYTWlPeJJRL25t9zF67PHRiIZlZ6zyHMcIz3PASepg5OC1W7o jA== Received: from nasanppmta03.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3t9qbptjcb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 25 Sep 2023 03:10:20 +0000 Received: from nasanex01a.na.qualcomm.com (nasanex01a.na.qualcomm.com [10.52.223.231]) by NASANPPMTA03.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 38P3AJwQ031384 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 25 Sep 2023 03:10:19 GMT Received: from [10.253.15.18] (10.80.80.8) by nasanex01a.na.qualcomm.com (10.52.223.231) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.36; Sun, 24 Sep 2023 20:10:16 -0700 Message-ID: Date: Mon, 25 Sep 2023 11:10:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v2 1/2] bus: mhi: host: Add spinlock to protect WP access when queueing TREs To: Jeffrey Hugo , CC: , , , , References: <1694594861-12691-1-git-send-email-quic_qianyu@quicinc.com> <1694594861-12691-2-git-send-email-quic_qianyu@quicinc.com> Content-Language: en-US From: Qiang Yu In-Reply-To: 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 nasanex01a.na.qualcomm.com (10.52.223.231) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: XJRBA2dU3AwcwaB447MKd2S34rCXhU9g X-Proofpoint-ORIG-GUID: XJRBA2dU3AwcwaB447MKd2S34rCXhU9g X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-09-24_21,2023-09-21_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 priorityscore=1501 adultscore=0 mlxlogscore=999 spamscore=0 malwarescore=0 impostorscore=0 lowpriorityscore=0 phishscore=0 suspectscore=0 clxscore=1015 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2309250018 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/22/2023 10:44 PM, Jeffrey Hugo wrote: > On 9/13/2023 2:47 AM, Qiang Yu wrote: >> From: Bhaumik Bhatt >> >> Protect WP accesses such that multiple threads queueing buffers for >> incoming data do not race and access the same WP twice. 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. >> >> Signed-off-by: Bhaumik Bhatt >> Signed-off-by: Qiang Yu >> --- >>   drivers/bus/mhi/host/main.c | 11 ++++++++++- >>   1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c >> index dcf627b..13c4b89 100644 >> --- a/drivers/bus/mhi/host/main.c >> +++ b/drivers/bus/mhi/host/main.c >> @@ -642,6 +642,7 @@ 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); > > This doesn't work due to the write_lock_irqsave(&mhi_chan->lock, > flags); on line 591. Write_lock_irqsave(&mhi_chan->lock, flags) is used in case of ev_code >= MHI_EV_CC_OOB. We only read_lock/read_unlock the mhi_chan while ev_code < MHI_EV_CC_OOB. > > I really don't like that we are unlocking the mhi_chan while still > using it.  It opens up a window where the mhi_chan state can be > updated between here and the client using the callback to queue a buf. > > Perhaps we need a new lock that just protects the wp, and needs to be > only grabbed while mhi_chan->lock is held? Since we have employed mhi_chan lock to protect the channel and what we are concerned here is that client may queue buf to a disabled or stopped channel, can we check channel state after getting mhi_chan->lock like line 595. We can add the check after getting write lock in mhi_gen_tre() and after getting read lock again here. > >>               /* notify client */ >>               mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result); >>   @@ -667,6 +668,7 @@ static int parse_xfer_event(struct >> mhi_controller *mhi_cntrl, >>                       kfree(buf_info->cb_buf); >>                   } >>               } >> +            read_lock_bh(&mhi_chan->lock); >>           } >>           break; >>       } /* CC_EOT */ >> @@ -1204,6 +1206,9 @@ int mhi_gen_tre(struct mhi_controller >> *mhi_cntrl, struct mhi_chan *mhi_chan, >>       int eot, eob, chain, bei; >>       int ret; >>   +    /* Protect accesses for reading and incrementing WP */ >> +    write_lock_bh(&mhi_chan->lock); >> + >>       buf_ring = &mhi_chan->buf_ring; >>       tre_ring = &mhi_chan->tre_ring; >>   @@ -1221,8 +1226,10 @@ int mhi_gen_tre(struct mhi_controller >> *mhi_cntrl, struct mhi_chan *mhi_chan, >>         if (!info->pre_mapped) { >>           ret = mhi_cntrl->map_single(mhi_cntrl, buf_info); >> -        if (ret) >> +        if (ret) { >> +            write_unlock_bh(&mhi_chan->lock); >>               return ret; >> +        } >>       } >>         eob = !!(flags & MHI_EOB); >> @@ -1239,6 +1246,8 @@ int mhi_gen_tre(struct mhi_controller >> *mhi_cntrl, struct mhi_chan *mhi_chan, >>       mhi_add_ring_element(mhi_cntrl, tre_ring); >>       mhi_add_ring_element(mhi_cntrl, buf_ring); >>   +    write_unlock_bh(&mhi_chan->lock); >> + >>       return 0; >>   } >