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=-16.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 4782FC433DB for ; Tue, 12 Jan 2021 19:57:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 15FCA206C3 for ; Tue, 12 Jan 2021 19:57:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436549AbhALT5L (ORCPT ); Tue, 12 Jan 2021 14:57:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:59592 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406911AbhALT5K (ORCPT ); Tue, 12 Jan 2021 14:57:10 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id CFC6F2311D; Tue, 12 Jan 2021 19:56:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610481390; bh=QE5TlA0Zxl753B5gdVcNGFk+7dY12Wdf4JiOwh97kMg=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=g7rCUMsrCQ2X7H1U08IwYi4wWoL7T0Y0P2bVTUayy+as8t43JqpteevAgBcUtGUrT Yl5xUX4tn1+dPYe9n6N8iLYDvcc8be4gL/pN8n52e2qIkSzAfrLQRbVsWcanB6sznc LpHZdOEXKD1PhbJjC74tI65kfcH828g38r5VClYtBJh0Sc6pFMvBPFe95ZDgB4M0KE FLTxnaaO3Q6+zfSP4WZcaCmW2Pcok3o21/+gLc5+LcDIfFDRwgaYg0PMdBnRTbQWGz VaMsU9+ZYgkJco6XYjMWvhEnFdG2FJHwXVOXdM85v+R2pf6QjCb4qr+lZd7irUVPuV NbY1tw+9emgeA== Message-ID: <47e7f34d0c8a14eefba6aac00b08fc39cab61679.camel@kernel.org> Subject: Re: [PATCH net-next v2 5/7] ibmvnic: serialize access to work queue From: Saeed Mahameed To: Sukadev Bhattiprolu , netdev@vger.kernel.org Cc: Dany Madden , Lijun Pan , Rick Lindsley Date: Tue, 12 Jan 2021 11:56:28 -0800 In-Reply-To: <20210112181441.206545-6-sukadev@linux.ibm.com> References: <20210112181441.206545-1-sukadev@linux.ibm.com> <20210112181441.206545-6-sukadev@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 2021-01-12 at 10:14 -0800, Sukadev Bhattiprolu wrote: > The work queue is used to queue reset requests like CHANGE-PARAM or > FAILOVER resets for the worker thread. When the adapter is being > removed > the adapter state is set to VNIC_REMOVING and the work queue is > flushed > so no new work is added. However the check for adapter being removed > is > racy in that the adapter can go into REMOVING state just after we > check > and we might end up adding work just as it is being flushed (or > after). > > Use a new spin lock, ->remove_lock to ensure that after (while) the > work > queue is (being) flushed, no new work is queued. > > A follow-on patch will convert the existing ->state_lock from a spin > lock > to to a mutex to allow us to hold it for longer periods of time. > Since > work can be scheduled from a tasklet, we cannot block on the mutex, > so > use a new spin lock. > > Fixes: 6954a9e4192b ("ibmvnic: Flush existing work items before > device removal") > Signed-off-by: Sukadev Bhattiprolu > --- > drivers/net/ethernet/ibm/ibmvnic.c | 15 ++++++++++++++- > drivers/net/ethernet/ibm/ibmvnic.h | 2 ++ > 2 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/ibm/ibmvnic.c > b/drivers/net/ethernet/ibm/ibmvnic.c > index ad551418ac63..7645df37e886 100644 > --- a/drivers/net/ethernet/ibm/ibmvnic.c > +++ b/drivers/net/ethernet/ibm/ibmvnic.c > @@ -2435,6 +2435,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter > *adapter, > enum ibmvnic_reset_reason reason) > { > struct net_device *netdev = adapter->netdev; > + unsigned long flags; > int ret; > > if (adapter->state == VNIC_PROBING) { > @@ -2443,6 +2444,8 @@ static int ibmvnic_reset(struct ibmvnic_adapter > *adapter, > goto err; > } > > + spin_lock_irqsave(&adapter->remove_lock, flags); > + > /* > * If failover is pending don't schedule any other reset. > * Instead let the failover complete. If there is already a > @@ -2465,8 +2468,9 @@ static int ibmvnic_reset(struct ibmvnic_adapter > *adapter, > netdev_dbg(adapter->netdev, "Scheduling reset (reason %d)\n", > reason); > schedule_work(&adapter->ibmvnic_reset); > > - return 0; > + ret = 0; > err: > + spin_unlock_irqrestore(&adapter->remove_lock, flags); > return -ret; > } > > @@ -5387,6 +5391,7 @@ static int ibmvnic_probe(struct vio_dev *dev, > const struct vio_device_id *id) > memset(&adapter->pending_resets, 0, sizeof(adapter- > >pending_resets)); > spin_lock_init(&adapter->rwi_lock); > spin_lock_init(&adapter->state_lock); > + spin_lock_init(&adapter->remove_lock); > mutex_init(&adapter->fw_lock); > init_completion(&adapter->init_done); > init_completion(&adapter->fw_done); > @@ -5467,7 +5472,15 @@ static int ibmvnic_remove(struct vio_dev *dev) > return -EBUSY; > } > > + /* If ibmvnic_reset() is scheduling a reset, wait for it to > + * finish. Then prevent it from scheduling any more resets > + * and have the reset functions ignore any resets that have > + * already been scheduled. > + */ > + spin_lock_irqsave(&adapter->remove_lock, flags); > adapter->state = VNIC_REMOVING; > + spin_unlock_irqrestore(&adapter->remove_lock, flags); > + Why irqsave/restore variants ? are you expecting this spinlock to be held in interruptcontext ? > spin_unlock_irqrestore(&adapter->state_lock, flags); > > flush_work(&adapter->ibmvnic_reset); > diff --git a/drivers/net/ethernet/ibm/ibmvnic.h > b/drivers/net/ethernet/ibm/ibmvnic.h > index 1179a95a3f92..2779696ade09 100644 > --- a/drivers/net/ethernet/ibm/ibmvnic.h > +++ b/drivers/net/ethernet/ibm/ibmvnic.h > @@ -1081,6 +1081,8 @@ struct ibmvnic_adapter { > spinlock_t rwi_lock; > enum ibmvnic_reset_reason pending_resets[VNIC_RESET_MAX-1]; > short next_reset; > + /* serialize ibmvnic_reset() and ibmvnic_remove() */ > + spinlock_t remove_lock; > struct work_struct ibmvnic_reset; > struct delayed_work ibmvnic_delayed_reset; > unsigned long resetting;