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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E498C38A2A for ; Thu, 7 May 2020 11:48:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED54020735 for ; Thu, 7 May 2020 11:48:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726093AbgEGLs1 (ORCPT ); Thu, 7 May 2020 07:48:27 -0400 Received: from mga06.intel.com ([134.134.136.31]:64619 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725903AbgEGLs0 (ORCPT ); Thu, 7 May 2020 07:48:26 -0400 IronPort-SDR: 0WDD4SYlelv/CMqDGbsa+Qd1M0WI661zriOKiJ/LvooJuDx2HTCleMYzxo4s8Xh6kVqvsU8E99 JqfAMf+jr5cw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2020 04:48:24 -0700 IronPort-SDR: i8kWrQpgWn75L4Fe2QfqwBPYtA7TVrOdZfwcIB8+RUtpWKVTAnVGtzTQxXUsavF0TyDLC53E6+ 81IX49BuWPHQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,363,1583222400"; d="scan'208";a="339328430" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.157]) ([10.237.72.157]) by orsmga001.jf.intel.com with ESMTP; 07 May 2020 04:48:21 -0700 Subject: Re: [PATCH V1 2/2] mmc: core: Fix recursive locking issue in CQE recovery path To: Veerabhadrarao Badiganti , ulf.hansson@linaro.org Cc: stummala@codeaurora.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Sarthak Garg , stable@vger.kernel.org, Baolin Wang , Yoshihiro Shimoda , Andreas Koop , Thomas Gleixner References: <1588775643-18037-1-git-send-email-vbadigan@codeaurora.org> <1588775643-18037-3-git-send-email-vbadigan@codeaurora.org> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: Date: Thu, 7 May 2020 14:48:42 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <1588775643-18037-3-git-send-email-vbadigan@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 6/05/20 5:34 pm, Veerabhadrarao Badiganti wrote: > From: Sarthak Garg > > Consider the following stack trace > > -001|raw_spin_lock_irqsave > -002|mmc_blk_cqe_complete_rq > -003|__blk_mq_complete_request(inline) > -003|blk_mq_complete_request(rq) > -004|mmc_cqe_timed_out(inline) > -004|mmc_mq_timed_out > > mmc_mq_timed_out acquires the queue_lock for the first > time. The mmc_blk_cqe_complete_rq function also tries to acquire > the same queue lock resulting in recursive locking where the task > is spinning for the same lock which it has already acquired leading > to watchdog bark. > > Fix this issue with the lock only for the required critical section. > > Cc: # v4.19+ > Suggested-by: Sahitya Tummala > Signed-off-by: Sarthak Garg > --- > drivers/mmc/core/queue.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c > index 25bee3d..72bef39 100644 > --- a/drivers/mmc/core/queue.c > +++ b/drivers/mmc/core/queue.c > @@ -107,7 +107,7 @@ static enum blk_eh_timer_return mmc_cqe_timed_out(struct request *req) > case MMC_ISSUE_DCMD: > if (host->cqe_ops->cqe_timeout(host, mrq, &recovery_needed)) { > if (recovery_needed) > - __mmc_cqe_recovery_notifier(mq); > + mmc_cqe_recovery_notifier(mrq); > return BLK_EH_RESET_TIMER; > } > /* No timeout (XXX: huh? comment doesn't make much sense) */ > @@ -131,12 +131,13 @@ static enum blk_eh_timer_return mmc_mq_timed_out(struct request *req, > > spin_lock_irqsave(&mq->lock, flags); > > - if (mq->recovery_needed || !mq->use_cqe || host->hsq_enabled) > + if (mq->recovery_needed || !mq->use_cqe || host->hsq_enabled) { > ret = BLK_EH_RESET_TIMER; > - else > + spin_unlock_irqrestore(&mq->lock, flags); > + } else { > + spin_unlock_irqrestore(&mq->lock, flags); > ret = mmc_cqe_timed_out(req); > - > - spin_unlock_irqrestore(&mq->lock, flags); > + } This looks good, but I think there needs to be another change also. I will send a patch for that, but in the meantime maybe you could straighten up the code flow through the spinlock e.g. spin_lock_irqsave(&mq->lock, flags); ignore = mq->recovery_needed || !mq->use_cqe || host->hsq_enabled; spin_unlock_irqrestore(&mq->lock, flags); return ignore ? BLK_EH_RESET_TIMER : mmc_cqe_timed_out(req); And add a fixes tag. > > return ret; > } >