be2iscsi: Fix soft lockup in mgmt_get_all_if_id path using bmbx

We are taking mbox_lock spinlock which disables pre-emption before we
poll for mbox completion. Waiting there with spinlock held in excess of
20s will cause soft lockup.

Actual fix is to change mbox_lock to mutex. The changes are done in
phases. This is the first part.

1. Changed mgmt_get_all_if_id to use MCC where after posting lock is
released.

2. Changed be_mbox_db_ready_wait to busy wait for 12s max and removed
wait_event_timeout. Added error handling code for IO reads.
OPCODE_COMMON_QUERY_FIRMWARE_CONFIG mbox command takes 8s time when
unreachable boot targets configured.

Signed-off-by: Jitendra Bhivare <jitendra.bhivare@avagotech.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/be2iscsi/be_cmds.c

@@ -587,47 +587,42 @@ int be_mcc_notify_wait(struct beiscsi_hba *phba)
  **/
 static int be_mbox_db_ready_wait(struct be_ctrl_info *ctrl)
 {
-#define BEISCSI_MBX_RDY_BIT_TIMEOUT	4000	/* 4sec */
+#define BEISCSI_MBX_RDY_BIT_TIMEOUT	12000	/* 12sec */
 	void __iomem *db = ctrl->db + MPU_MAILBOX_DB_OFFSET;
 	struct beiscsi_hba *phba = pci_get_drvdata(ctrl->pdev);
 	unsigned long timeout;
-	bool read_flag = false;
-	int ret = 0, i;
 	u32 ready;
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(rdybit_check_q);
-
-	if (beiscsi_error(phba))
-		return -EIO;
-
-	timeout = jiffies + (HZ * 110);
 
+	/*
+	 * This BMBX busy wait path is used during init only.
+	 * For the commands executed during init, 5s should suffice.
+	 */
+	timeout = jiffies + msecs_to_jiffies(BEISCSI_MBX_RDY_BIT_TIMEOUT);
 	do {
-		for (i = 0; i < BEISCSI_MBX_RDY_BIT_TIMEOUT; i++) {
-			ready = ioread32(db) & MPU_MAILBOX_DB_RDY_MASK;
-			if (ready) {
-				read_flag = true;
-				break;
-			}
-			mdelay(1);
-		}
+		if (beiscsi_error(phba))
+			return -EIO;
 
-		if (!read_flag) {
-			wait_event_timeout(rdybit_check_q,
-					  (read_flag != true),
-					   HZ * 5);
-		}
-	} while ((time_before(jiffies, timeout)) && !read_flag);
+		ready = ioread32(db);
+		if (ready == 0xffffffff)
+			return -EIO;
 
-	if (!read_flag) {
-		beiscsi_log(phba, KERN_ERR,
-			    BEISCSI_LOG_CONFIG | BEISCSI_LOG_MBOX,
-			    "BC_%d : FW Timed Out\n");
-			phba->fw_timeout = true;
-			beiscsi_ue_detect(phba);
-			ret = -EBUSY;
-	}
+		ready &= MPU_MAILBOX_DB_RDY_MASK;
+		if (ready)
+			return 0;
 
-	return ret;
+		if (time_after(jiffies, timeout))
+			break;
+		mdelay(1);
+	} while (!ready);
+
+	beiscsi_log(phba, KERN_ERR,
+			BEISCSI_LOG_CONFIG | BEISCSI_LOG_MBOX,
+			"BC_%d : FW Timed Out\n");
+
+	phba->fw_timeout = true;
+	beiscsi_ue_detect(phba);
+
+	return -EBUSY;
 }
 
 /*
@@ -674,6 +669,9 @@ int be_mbox_notify(struct be_ctrl_info *ctrl)
 	if (status)
 		return status;
 
+	/* RDY is set; small delay before CQE read. */
+	udelay(1);
+
 	if (be_mcc_compl_is_new(compl)) {
 		status = be_mcc_compl_process(ctrl, &mbox->compl);
 		be_mcc_compl_use(compl);

drivers/scsi/be2iscsi/be_mgmt.c

@@ -809,27 +809,39 @@ int mgmt_open_connection(struct beiscsi_hba *phba,
 unsigned int mgmt_get_all_if_id(struct beiscsi_hba *phba)
 {
 	struct be_ctrl_info *ctrl = &phba->ctrl;
-	struct be_mcc_wrb *wrb = wrb_from_mbox(&ctrl->mbox_mem);
-	struct be_cmd_get_all_if_id_req *req = embedded_payload(wrb);
-	struct be_cmd_get_all_if_id_req *pbe_allid = req;
+	struct be_mcc_wrb *wrb;
+	struct be_cmd_get_all_if_id_req *req;
+	struct be_cmd_get_all_if_id_req *pbe_allid;
+	unsigned int tag;
 	int status = 0;
 
-	memset(wrb, 0, sizeof(*wrb));
-
 	spin_lock(&ctrl->mbox_lock);
+	tag = alloc_mcc_tag(phba);
+	if (!tag) {
+		spin_unlock(&ctrl->mbox_lock);
+		return -ENOMEM;
+	}
+
+	wrb = wrb_from_mccq(phba);
+	req = embedded_payload(wrb);
+	wrb->tag0 |= tag;
 
 	be_wrb_hdr_prepare(wrb, sizeof(*req), true, 0);
 	be_cmd_hdr_prepare(&req->hdr, CMD_SUBSYSTEM_ISCSI,
 			   OPCODE_COMMON_ISCSI_NTWK_GET_ALL_IF_ID,
 			   sizeof(*req));
-	status = be_mbox_notify(ctrl);
-	if (!status)
-		phba->interface_handle = pbe_allid->if_hndl_list[0];
-	else {
+	be_mcc_notify(phba);
+	spin_unlock(&ctrl->mbox_lock);
+
+	status = beiscsi_mccq_compl(phba, tag, &wrb, NULL);
+	if (status) {
 		beiscsi_log(phba, KERN_WARNING, BEISCSI_LOG_CONFIG,
 			    "BG_%d : Failed in mgmt_get_all_if_id\n");
+		return -EBUSY;
 	}
-	spin_unlock(&ctrl->mbox_lock);
+
+	pbe_allid = embedded_payload(wrb);
+	phba->interface_handle = pbe_allid->if_hndl_list[0];
 
 	return status;
 }