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Fri, 4 Dec 2020 21:35:25 +0000 (GMT) Subject: Re: [PATCH v3 18/18] ibmvfc: drop host lock when completing commands in CRQ To: Tyrel Datwyler , james.bottomley@hansenpartnership.com Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, brking@linux.ibm.com References: <20201203020806.14747-1-tyreld@linux.ibm.com> <20201203020806.14747-19-tyreld@linux.ibm.com> From: Brian King Message-ID: Date: Fri, 4 Dec 2020 15:35:25 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201203020806.14747-19-tyreld@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-12-04_11:2020-12-04,2020-12-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 adultscore=0 spamscore=0 impostorscore=0 mlxscore=0 phishscore=0 mlxlogscore=999 clxscore=1015 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012040119 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/2/20 8:08 PM, Tyrel Datwyler wrote: > The legacy CRQ holds the host lock the even while completing commands. > This presents a problem when in legacy single queue mode and > nr_hw_queues is greater than one since calling scsi_done() introduces > the potential for deadlock. > > If nr_hw_queues is greater than one drop the hostlock in the legacy CRQ > path when completing a command. > > Signed-off-by: Tyrel Datwyler > --- > drivers/scsi/ibmvscsi/ibmvfc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c > index e499599662ec..e2200bdff2be 100644 > --- a/drivers/scsi/ibmvscsi/ibmvfc.c > +++ b/drivers/scsi/ibmvscsi/ibmvfc.c > @@ -2969,6 +2969,7 @@ static void ibmvfc_handle_crq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost) > { > long rc; > struct ibmvfc_event *evt = (struct ibmvfc_event *)be64_to_cpu(crq->ioba); > + unsigned long flags; > > switch (crq->valid) { > case IBMVFC_CRQ_INIT_RSP: > @@ -3039,7 +3040,12 @@ static void ibmvfc_handle_crq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost) > del_timer(&evt->timer); > list_del(&evt->queue); > ibmvfc_trc_end(evt); > - evt->done(evt); > + if (nr_scsi_hw_queues > 1) { > + spin_unlock_irqrestore(vhost->host->host_lock, flags); > + evt->done(evt); > + spin_lock_irqsave(vhost->host->host_lock, flags); > + } else > + evt->done(evt); Similar comment here as previously. The flags parameter is an output for spin_lock_irqsave but an input for spin_unlock_irqrestore. You'll need to rethink the locking here. You could just do a spin_unlock_irq / spin_lock_irq here and that would probably be OK, but probably isn't the best. > } > > /** > -- Brian King Power Linux I/O IBM Linux Technology Center 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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 D4168C433FE for ; Fri, 4 Dec 2020 21:38:33 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 14A7522BE8 for ; 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Fri, 4 Dec 2020 21:35:25 +0000 (GMT) Subject: Re: [PATCH v3 18/18] ibmvfc: drop host lock when completing commands in CRQ To: Tyrel Datwyler , james.bottomley@hansenpartnership.com References: <20201203020806.14747-1-tyreld@linux.ibm.com> <20201203020806.14747-19-tyreld@linux.ibm.com> From: Brian King Message-ID: Date: Fri, 4 Dec 2020 15:35:25 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201203020806.14747-19-tyreld@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-12-04_11:2020-12-04, 2020-12-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 adultscore=0 spamscore=0 impostorscore=0 mlxscore=0 phishscore=0 mlxlogscore=999 clxscore=1015 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012040119 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: brking@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-scsi@vger.kernel.org, martin.petersen@oracle.com, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 12/2/20 8:08 PM, Tyrel Datwyler wrote: > The legacy CRQ holds the host lock the even while completing commands. > This presents a problem when in legacy single queue mode and > nr_hw_queues is greater than one since calling scsi_done() introduces > the potential for deadlock. > > If nr_hw_queues is greater than one drop the hostlock in the legacy CRQ > path when completing a command. > > Signed-off-by: Tyrel Datwyler > --- > drivers/scsi/ibmvscsi/ibmvfc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c > index e499599662ec..e2200bdff2be 100644 > --- a/drivers/scsi/ibmvscsi/ibmvfc.c > +++ b/drivers/scsi/ibmvscsi/ibmvfc.c > @@ -2969,6 +2969,7 @@ static void ibmvfc_handle_crq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost) > { > long rc; > struct ibmvfc_event *evt = (struct ibmvfc_event *)be64_to_cpu(crq->ioba); > + unsigned long flags; > > switch (crq->valid) { > case IBMVFC_CRQ_INIT_RSP: > @@ -3039,7 +3040,12 @@ static void ibmvfc_handle_crq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost) > del_timer(&evt->timer); > list_del(&evt->queue); > ibmvfc_trc_end(evt); > - evt->done(evt); > + if (nr_scsi_hw_queues > 1) { > + spin_unlock_irqrestore(vhost->host->host_lock, flags); > + evt->done(evt); > + spin_lock_irqsave(vhost->host->host_lock, flags); > + } else > + evt->done(evt); Similar comment here as previously. The flags parameter is an output for spin_lock_irqsave but an input for spin_unlock_irqrestore. You'll need to rethink the locking here. You could just do a spin_unlock_irq / spin_lock_irq here and that would probably be OK, but probably isn't the best. > } > > /** > -- Brian King Power Linux I/O IBM Linux Technology Center