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 C2989E6FE3C for ; Fri, 22 Sep 2023 14:44:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231309AbjIVOoU (ORCPT ); Fri, 22 Sep 2023 10:44:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230339AbjIVOoS (ORCPT ); Fri, 22 Sep 2023 10:44:18 -0400 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7335DC6; Fri, 22 Sep 2023 07:44:12 -0700 (PDT) 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 38MEBvdu025832; Fri, 22 Sep 2023 14:44:06 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=LbFeoloWRxRrwi9BvqCwJ3WHW3JbWo1zCUDcGy9w4i8=; b=PDl2TtNwP9vcGPNS2zIcEmknyPJHYcGx+264sOsxdMWRLKArd9ZfJqVWjgwr5FwAQysh 5ZDHLk5vXxat30e1VL8TQ8ZqwIrev4KZv4I/lV49oBHTLMlH34CeKjnWoV2y9kqrJVQd +0okmgiGF0MX6+5wF07xLO5ej3qlO9Br1doHuzQjTbATtilF8Nt7c/gBn7tzfGbPay+W VY2n91QTuSIGEuQtG7j6Dzxp7l7ickzHJnGwv05RMIKrVkKmZSa0AcgT29h2eSitoemn UuaBCVK2YCWmg5+cllZ0kR67kGvuQ8gp42MuxulIppSRav0vJvKnP32PiLF77oWNDW0f Aw== Received: from nalasppmta04.qualcomm.com (Global_NAT1.qualcomm.com [129.46.96.20]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3t8u9ha169-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 22 Sep 2023 14:44:06 +0000 Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA04.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 38MEi58N026898 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 22 Sep 2023 14:44:05 GMT Received: from [10.226.59.182] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.36; Fri, 22 Sep 2023 07:44:04 -0700 Message-ID: Date: Fri, 22 Sep 2023 08:44:03 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.0 Subject: Re: [PATCH v2 1/2] bus: mhi: host: Add spinlock to protect WP access when queueing TREs Content-Language: en-US To: Qiang Yu , CC: , , , , References: <1694594861-12691-1-git-send-email-quic_qianyu@quicinc.com> <1694594861-12691-2-git-send-email-quic_qianyu@quicinc.com> From: Jeffrey Hugo In-Reply-To: <1694594861-12691-2-git-send-email-quic_qianyu@quicinc.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: hweOo_-hxqLmD1dGwUGyMy4GAL7LCy1l X-Proofpoint-ORIG-GUID: hweOo_-hxqLmD1dGwUGyMy4GAL7LCy1l 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=2023-09-22_13,2023-09-21_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 bulkscore=0 spamscore=0 priorityscore=1501 phishscore=0 suspectscore=0 malwarescore=0 clxscore=1011 mlxlogscore=814 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2309220126 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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? > /* 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; > } >