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Wed, 2 Dec 2020 22:28:43 +0000 (GMT) Subject: Re: [PATCH v2 06/17] ibmvfc: add handlers to drain and complete Sub-CRQ responses To: Brian King , james.bottomley@hansenpartnership.com References: <20201202005329.4538-1-tyreld@linux.ibm.com> <20201202005329.4538-7-tyreld@linux.ibm.com> <32b08be7-4c1e-a572-c70c-1f182f1d0259@linux.vnet.ibm.com> From: Tyrel Datwyler Message-ID: <38838bf6-5976-14de-e3a7-37f4c735d89b@linux.ibm.com> Date: Wed, 2 Dec 2020 14:28:42 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <32b08be7-4c1e-a572-c70c-1f182f1d0259@linux.vnet.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=2020-12-02_13:2020-11-30, 2020-12-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 malwarescore=0 spamscore=0 impostorscore=0 priorityscore=1501 mlxscore=0 bulkscore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 mlxlogscore=999 suspectscore=2 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012020130 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 7:46 AM, Brian King wrote: > On 12/1/20 6:53 PM, Tyrel Datwyler wrote: >> The logic for iterating over the Sub-CRQ responses is similiar to that >> of the primary CRQ. Add the necessary handlers for processing those >> responses. >> >> Signed-off-by: Tyrel Datwyler >> --- >> drivers/scsi/ibmvscsi/ibmvfc.c | 77 ++++++++++++++++++++++++++++++++++ >> 1 file changed, 77 insertions(+) >> >> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c >> index 97f00fefa809..e9da3f60c793 100644 >> --- a/drivers/scsi/ibmvscsi/ibmvfc.c >> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c >> @@ -3381,6 +3381,83 @@ static int ibmvfc_toggle_scrq_irq(struct ibmvfc_sub_queue *scrq, int enable) >> return rc; >> } >> >> +static void ibmvfc_handle_scrq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost) >> +{ >> + struct ibmvfc_event *evt = (struct ibmvfc_event *)be64_to_cpu(crq->ioba); >> + unsigned long flags; >> + >> + switch (crq->valid) { >> + case IBMVFC_CRQ_CMD_RSP: >> + break; >> + case IBMVFC_CRQ_XPORT_EVENT: >> + return; >> + default: >> + dev_err(vhost->dev, "Got and invalid message type 0x%02x\n", crq->valid); >> + return; >> + } >> + >> + /* The only kind of payload CRQs we should get are responses to >> + * things we send. Make sure this response is to something we >> + * actually sent >> + */ >> + if (unlikely(!ibmvfc_valid_event(&vhost->pool, evt))) { >> + dev_err(vhost->dev, "Returned correlation_token 0x%08llx is invalid!\n", >> + crq->ioba); >> + return; >> + } >> + >> + if (unlikely(atomic_read(&evt->free))) { >> + dev_err(vhost->dev, "Received duplicate correlation_token 0x%08llx!\n", >> + crq->ioba); >> + return; >> + } >> + >> + spin_lock_irqsave(vhost->host->host_lock, flags); >> + del_timer(&evt->timer); >> + list_del(&evt->queue); >> + ibmvfc_trc_end(evt); >> + spin_unlock_irqrestore(vhost->host->host_lock, flags); >> + evt->done(evt); >> +} >> + >> +static struct ibmvfc_crq *ibmvfc_next_scrq(struct ibmvfc_sub_queue *scrq) >> +{ >> + struct ibmvfc_crq *crq; >> + >> + crq = &scrq->msgs[scrq->cur].crq; >> + if (crq->valid & 0x80) { >> + if (++scrq->cur == scrq->size) > > You are incrementing the cur pointer without any locks held. Although > unlikely, could you also be in ibmvfc_reset_crq in another thread? > If so, you'd have a subtle race condition here where the cur pointer could > be read, then ibmvfc_reset_crq writes it to zero, then this thread > writes it to a non zero value, which would then cause you to be out of > sync with the VIOS as to where the cur pointer is. Oof, yeah I was previously holding the lock the whole time, but switched it up once I realized I can't complete a scsi command with the lock held, and got a little too loose with it. -Tyrel > >> + scrq->cur = 0; >> + rmb(); >> + } else >> + crq = NULL; >> + >> + return crq; >> +} >> + > > >