[PATCH 5/9] hpsa: remove scan thread

["Stephen M. Cameron" <scameron@beardog.cce.hp.com>]

From: Mike Miller <mikem@beardog.cce.hp.com>

hpsa: remove scan thread
The intent of the scan thread was to allow a UNIT ATTENTION/LUN
DATA CHANGED condition encountered in the interrupt handler
to trigger a rescan of devices, which can't be done in interrupt
context.  However, we weren't able to get this to work, due to
multiple such UNIT ATTENTION conditions arriving during the rescan,
during updating of the SCSI mid layer, etc.  There's no way to tell
the devices, "stand still while I scan you!"  Since it doesn't work,
there's no point in having the thread, as the rescan triggered via
ioctl or sysfs can be done without such a thread.

Signed-off-by: Mike Miller <mikem@beardog.cce.hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
---
 drivers/scsi/hpsa.c |  167 +--------------------------------------------------
 drivers/scsi/hpsa.h |    3 -
 2 files changed, 4 insertions(+), 166 deletions(-)

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index a72a18e..3d43bb2 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -53,7 +53,7 @@
 #include "hpsa.h"
 
 /* HPSA_DRIVER_VERSION must be 3 byte values (0-255) separated by '.' */
-#define HPSA_DRIVER_VERSION "2.0.1-3"
+#define HPSA_DRIVER_VERSION "2.0.2-1"
 #define DRIVER_NAME "HP HPSA Driver (v " HPSA_DRIVER_VERSION ")"
 
 /* How long to wait (in milliseconds) for board to go into simple mode */
@@ -212,133 +212,6 @@ static inline struct ctlr_info *shost_to_hba(struct Scsi_Host *sh)
 	return (struct ctlr_info *) *priv;
 }
 
-static struct task_struct *hpsa_scan_thread;
-static DEFINE_MUTEX(hpsa_scan_mutex);
-static LIST_HEAD(hpsa_scan_q);
-static int hpsa_scan_func(void *data);
-
-/**
- * add_to_scan_list() - add controller to rescan queue
- * @h:		      Pointer to the controller.
- *
- * Adds the controller to the rescan queue if not already on the queue.
- *
- * returns 1 if added to the queue, 0 if skipped (could be on the
- * queue already, or the controller could be initializing or shutting
- * down).
- **/
-static int add_to_scan_list(struct ctlr_info *h)
-{
-	struct ctlr_info *test_h;
-	int found = 0;
-	int ret = 0;
-
-	if (h->busy_initializing)
-		return 0;
-
-	/*
-	 * If we don't get the lock, it means the driver is unloading
-	 * and there's no point in scheduling a new scan.
-	 */
-	if (!mutex_trylock(&h->busy_shutting_down))
-		return 0;
-
-	mutex_lock(&hpsa_scan_mutex);
-	list_for_each_entry(test_h, &hpsa_scan_q, scan_list) {
-		if (test_h == h) {
-			found = 1;
-			break;
-		}
-	}
-	if (!found && !h->busy_scanning) {
-		INIT_COMPLETION(h->scan_wait);
-		list_add_tail(&h->scan_list, &hpsa_scan_q);
-		ret = 1;
-	}
-	mutex_unlock(&hpsa_scan_mutex);
-	mutex_unlock(&h->busy_shutting_down);
-
-	return ret;
-}
-
-/**
- * remove_from_scan_list() - remove controller from rescan queue
- * @h:			   Pointer to the controller.
- *
- * Removes the controller from the rescan queue if present. Blocks if
- * the controller is currently conducting a rescan.  The controller
- * can be in one of three states:
- * 1. Doesn't need a scan
- * 2. On the scan list, but not scanning yet (we remove it)
- * 3. Busy scanning (and not on the list). In this case we want to wait for
- *    the scan to complete to make sure the scanning thread for this
- *    controller is completely idle.
- **/
-static void remove_from_scan_list(struct ctlr_info *h)
-{
-	struct ctlr_info *test_h, *tmp_h;
-
-	mutex_lock(&hpsa_scan_mutex);
-	list_for_each_entry_safe(test_h, tmp_h, &hpsa_scan_q, scan_list) {
-		if (test_h == h) { /* state 2. */
-			list_del(&h->scan_list);
-			complete_all(&h->scan_wait);
-			mutex_unlock(&hpsa_scan_mutex);
-			return;
-		}
-	}
-	if (h->busy_scanning) { /* state 3. */
-		mutex_unlock(&hpsa_scan_mutex);
-		wait_for_completion(&h->scan_wait);
-	} else { /* state 1, nothing to do. */
-		mutex_unlock(&hpsa_scan_mutex);
-	}
-}
-
-/* hpsa_scan_func() - kernel thread used to rescan controllers
- * @data:	 Ignored.
- *
- * A kernel thread used scan for drive topology changes on
- * controllers. The thread processes only one controller at a time
- * using a queue.  Controllers are added to the queue using
- * add_to_scan_list() and removed from the queue either after done
- * processing or using remove_from_scan_list().
- *
- * returns 0.
- **/
-static int hpsa_scan_func(__attribute__((unused)) void *data)
-{
-	struct ctlr_info *h;
-	int host_no;
-
-	while (1) {
-		set_current_state(TASK_INTERRUPTIBLE);
-		schedule();
-		if (kthread_should_stop())
-			break;
-
-		while (1) {
-			mutex_lock(&hpsa_scan_mutex);
-			if (list_empty(&hpsa_scan_q)) {
-				mutex_unlock(&hpsa_scan_mutex);
-				break;
-			}
-			h = list_entry(hpsa_scan_q.next, struct ctlr_info,
-					scan_list);
-			list_del(&h->scan_list);
-			h->busy_scanning = 1;
-			mutex_unlock(&hpsa_scan_mutex);
-			host_no = h->scsi_host ?  h->scsi_host->host_no : -1;
-			hpsa_scan_start(h->scsi_host);
-			complete_all(&h->scan_wait);
-			mutex_lock(&hpsa_scan_mutex);
-			h->busy_scanning = 0;
-			mutex_unlock(&hpsa_scan_mutex);
-		}
-	}
-	return 0;
-}
-
 static int check_for_unit_attention(struct ctlr_info *h,
 	struct CommandList *c)
 {
@@ -356,21 +229,8 @@ static int check_for_unit_attention(struct ctlr_info *h,
 		break;
 	case REPORT_LUNS_CHANGED:
 		dev_warn(&h->pdev->dev, "hpsa%d: report LUN data "
-			"changed\n", h->ctlr);
+			"changed, action required\n", h->ctlr);
 	/*
-	 * Here, we could call add_to_scan_list and wake up the scan thread,
-	 * except that it's quite likely that we will get more than one
-	 * REPORT_LUNS_CHANGED condition in quick succession, which means
-	 * that those which occur after the first one will likely happen
-	 * *during* the hpsa_scan_thread's rescan.  And the rescan code is not
-	 * robust enough to restart in the middle, undoing what it has already
-	 * done, and it's not clear that it's even possible to do this, since
-	 * part of what it does is notify the SCSI mid layer, which starts
-	 * doing it's own i/o to read partition tables and so on, and the
-	 * driver doesn't have visibility to know what might need undoing.
-	 * In any event, if possible, it is horribly complicated to get right
-	 * so we just don't do it for now.
-	 *
 	 * Note: this REPORT_LUNS_CHANGED condition only occurs on the MSA2012.
 	 */
 		break;
@@ -397,10 +257,7 @@ static ssize_t host_store_rescan(struct device *dev,
 	struct ctlr_info *h;
 	struct Scsi_Host *shost = class_to_shost(dev);
 	h = shost_to_hba(shost);
-	if (add_to_scan_list(h)) {
-		wake_up_process(hpsa_scan_thread);
-		wait_for_completion_interruptible(&h->scan_wait);
-	}
+	hpsa_scan_start(h->scsi_host);
 	return count;
 }
 
@@ -3553,8 +3410,6 @@ static int __devinit hpsa_init_one(struct pci_dev *pdev,
 	h->busy_initializing = 1;
 	INIT_HLIST_HEAD(&h->cmpQ);
 	INIT_HLIST_HEAD(&h->reqQ);
-	mutex_init(&h->busy_shutting_down);
-	init_completion(&h->scan_wait);
 	rc = hpsa_pci_init(h, pdev);
 	if (rc != 0)
 		goto clean1;
@@ -3702,8 +3557,6 @@ static void __devexit hpsa_remove_one(struct pci_dev *pdev)
 		return;
 	}
 	h = pci_get_drvdata(pdev);
-	mutex_lock(&h->busy_shutting_down);
-	remove_from_scan_list(h);
 	hpsa_unregister_scsi(h);	/* unhook from SCSI subsystem */
 	hpsa_shutdown(pdev);
 	iounmap(h->vaddr);
@@ -3724,7 +3577,6 @@ static void __devexit hpsa_remove_one(struct pci_dev *pdev)
 	 */
 	pci_release_regions(pdev);
 	pci_set_drvdata(pdev, NULL);
-	mutex_unlock(&h->busy_shutting_down);
 	kfree(h);
 }
 
@@ -3878,23 +3730,12 @@ clean_up:
  */
 static int __init hpsa_init(void)
 {
-	int err;
-	/* Start the scan thread */
-	hpsa_scan_thread = kthread_run(hpsa_scan_func, NULL, "hpsa_scan");
-	if (IS_ERR(hpsa_scan_thread)) {
-		err = PTR_ERR(hpsa_scan_thread);
-		return -ENODEV;
-	}
-	err = pci_register_driver(&hpsa_pci_driver);
-	if (err)
-		kthread_stop(hpsa_scan_thread);
-	return err;
+	return pci_register_driver(&hpsa_pci_driver);
 }
 
 static void __exit hpsa_cleanup(void)
 {
 	pci_unregister_driver(&hpsa_pci_driver);
-	kthread_stop(hpsa_scan_thread);
 }
 
 module_init(hpsa_init);
diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index a0502b3..fc15215 100644
--- a/drivers/scsi/hpsa.h
+++ b/drivers/scsi/hpsa.h
@@ -97,9 +97,6 @@ struct ctlr_info {
 	int			scan_finished;
 	spinlock_t		scan_lock;
 	wait_queue_head_t	scan_wait_queue;
-	struct mutex		busy_shutting_down;
-	struct list_head	scan_list;
-	struct completion	scan_wait;
 
 	struct Scsi_Host *scsi_host;
 	spinlock_t devlock; /* to protect hba[ctlr]->dev[];  */