scsi: ipr: System hung while dlpar adding primary ipr adapter back

While dlpar adding primary ipr adapter back, driver goes through adapter
initialization then schedule ipr_worker_thread to start te disk scan by
dropping the host lock, calling scsi_add_device.  Then get the adapter reset
request again, so driver does scsi_block_requests, this will cause the
scsi_add_device get hung until we unblock. But we can't run ipr_worker_thread
to do the unblock because its stuck in scsi_add_device.

This patch fixes the issue.

[mkp: typo and whitespace fixes]

Signed-off-by: Wen Xiong <wenxiong@linux.vnet.ibm.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ipr.c

@@ -3335,64 +3335,19 @@ static void ipr_release_dump(struct kref *kref)
 	LEAVE;
 }
 
-/**
+static void ipr_add_remove_thread(struct work_struct *work)
- * ipr_worker_thread - Worker thread
- * @work:		ioa config struct
- *
- * Called at task level from a work thread. This function takes care
- * of adding and removing device from the mid-layer as configuration
- * changes are detected by the adapter.
- *
- * Return value:
- * 	nothing
- **/
-static void ipr_worker_thread(struct work_struct *work)
 {
 	unsigned long lock_flags;
 	struct ipr_resource_entry *res;
 	struct scsi_device *sdev;
-	struct ipr_dump *dump;
 	struct ipr_ioa_cfg *ioa_cfg =
-		container_of(work, struct ipr_ioa_cfg, work_q);
+		container_of(work, struct ipr_ioa_cfg, scsi_add_work_q);
 	u8 bus, target, lun;
 	int did_work;
 
 	ENTER;
 	spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
 
-	if (ioa_cfg->sdt_state == READ_DUMP) {
-		dump = ioa_cfg->dump;
-		if (!dump) {
-			spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
-			return;
-		}
-		kref_get(&dump->kref);
-		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
-		ipr_get_ioa_dump(ioa_cfg, dump);
-		kref_put(&dump->kref, ipr_release_dump);
-
-		spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
-		if (ioa_cfg->sdt_state == DUMP_OBTAINED && !ioa_cfg->dump_timeout)
-			ipr_initiate_ioa_reset(ioa_cfg, IPR_SHUTDOWN_NONE);
-		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
-		return;
-	}
-
-	if (ioa_cfg->scsi_unblock) {
-		ioa_cfg->scsi_unblock = 0;
-		ioa_cfg->scsi_blocked = 0;
-		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
-		scsi_unblock_requests(ioa_cfg->host);
-		spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
-		if (ioa_cfg->scsi_blocked)
-			scsi_block_requests(ioa_cfg->host);
-	}
-
-	if (!ioa_cfg->scan_enabled) {
-		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
-		return;
-	}
-
 restart:
 	do {
 		did_work = 0;
@@ -3439,6 +3394,66 @@ static void ipr_worker_thread(struct work_struct *work)
 	LEAVE;
 }
 
+/**
+ * ipr_worker_thread - Worker thread
+ * @work:		ioa config struct
+ *
+ * Called at task level from a work thread. This function takes care
+ * of adding and removing device from the mid-layer as configuration
+ * changes are detected by the adapter.
+ *
+ * Return value:
+ * 	nothing
+ **/
+static void ipr_worker_thread(struct work_struct *work)
+{
+	unsigned long lock_flags;
+	struct ipr_dump *dump;
+	struct ipr_ioa_cfg *ioa_cfg =
+		container_of(work, struct ipr_ioa_cfg, work_q);
+
+	ENTER;
+	spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
+
+	if (ioa_cfg->sdt_state == READ_DUMP) {
+		dump = ioa_cfg->dump;
+		if (!dump) {
+			spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+			return;
+		}
+		kref_get(&dump->kref);
+		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+		ipr_get_ioa_dump(ioa_cfg, dump);
+		kref_put(&dump->kref, ipr_release_dump);
+
+		spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
+		if (ioa_cfg->sdt_state == DUMP_OBTAINED && !ioa_cfg->dump_timeout)
+			ipr_initiate_ioa_reset(ioa_cfg, IPR_SHUTDOWN_NONE);
+		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+		return;
+	}
+
+	if (ioa_cfg->scsi_unblock) {
+		ioa_cfg->scsi_unblock = 0;
+		ioa_cfg->scsi_blocked = 0;
+		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+		scsi_unblock_requests(ioa_cfg->host);
+		spin_lock_irqsave(ioa_cfg->host->host_lock, lock_flags);
+		if (ioa_cfg->scsi_blocked)
+			scsi_block_requests(ioa_cfg->host);
+	}
+
+	if (!ioa_cfg->scan_enabled) {
+		spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+		return;
+	}
+
+	schedule_work(&ioa_cfg->scsi_add_work_q);
+
+	spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+	LEAVE;
+}
+
 #ifdef CONFIG_SCSI_IPR_TRACE
 /**
  * ipr_read_trace - Dump the adapter trace
@@ -9933,6 +9948,7 @@ static void ipr_init_ioa_cfg(struct ipr_ioa_cfg *ioa_cfg,
 	INIT_LIST_HEAD(&ioa_cfg->free_res_q);
 	INIT_LIST_HEAD(&ioa_cfg->used_res_q);
 	INIT_WORK(&ioa_cfg->work_q, ipr_worker_thread);
+	INIT_WORK(&ioa_cfg->scsi_add_work_q, ipr_add_remove_thread);
 	init_waitqueue_head(&ioa_cfg->reset_wait_q);
 	init_waitqueue_head(&ioa_cfg->msi_wait_q);
 	init_waitqueue_head(&ioa_cfg->eeh_wait_q);

drivers/scsi/ipr.h

@@ -1575,6 +1575,7 @@ struct ipr_ioa_cfg {
 	u8 saved_mode_page_len;
 
 	struct work_struct work_q;
+	struct work_struct scsi_add_work_q;
 	struct workqueue_struct *reset_work_q;
 
 	wait_queue_head_t reset_wait_q;