cciss: Use one scan thread per controller and fix hang during rmmod

Replace the use of one scan kthread per controller with one per driver.
Use a queue to hold a list of controllers that need to be rescanned with
routines to add and remove controllers from the queue.

Fix locking and completion handling to prevent a hang during rmmod.

Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Acked-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 136 insertions, 20 deletions

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index f162f96c36e6..4fb63b898798 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -40,6 +40,7 @@
 #include <linux/hdreg.h>
 #include <linux/spinlock.h>
 #include <linux/compat.h>
+#include <linux/mutex.h>
 #include <asm/uaccess.h>
 #include <asm/io.h>
 
@@ -156,6 +157,10 @@ static struct board_type products[] = {
 
 static ctlr_info_t *hba[MAX_CTLR];
 
+static struct task_struct *cciss_scan_thread;
+static DEFINE_MUTEX(scan_mutex);
+static LIST_HEAD(scan_q);
+
 static void do_cciss_request(struct request_queue *q);
 static irqreturn_t do_cciss_intr(int irq, void *dev_id);
 static int cciss_open(struct block_device *bdev, fmode_t mode);
@@ -3233,20 +3238,121 @@ static irqreturn_t do_cciss_intr(int irq, void *dev_id)
         return IRQ_HANDLED;
 }
 
+/**
+ * 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 (!mutex_trylock(&h->busy_shutting_down))
+                return 0;
+
+        mutex_lock(&scan_mutex);
+        list_for_each_entry(test_h, &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, &scan_q);
+                ret = 1;
+        }
+        mutex_unlock(&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.
+ **/
+static void remove_from_scan_list(struct ctlr_info *h)
+{
+        struct ctlr_info *test_h, *tmp_h;
+        int scanning = 0;
+
+        mutex_lock(&scan_mutex);
+        list_for_each_entry_safe(test_h, tmp_h, &scan_q, scan_list) {
+                if (test_h == h) {
+                        list_del(&h->scan_list);
+                        complete_all(&h->scan_wait);
+                        mutex_unlock(&scan_mutex);
+                        return;
+                }
+        }
+        if (&h->busy_scanning)
+                scanning = 0;
+        mutex_unlock(&scan_mutex);
+
+        if (scanning)
+                wait_for_completion(&h->scan_wait);
+}
+
+/**
+ * scan_thread() - 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 scan_thread(void *data)
 {
-        ctlr_info_t *h = data;
-        int rc;
-        DECLARE_COMPLETION_ONSTACK(wait);
-        h->rescan_wait = &wait;
+        struct ctlr_info *h;
 
-        for (;;) {
-                rc = wait_for_completion_interruptible(&wait);
+        while (1) {
+                set_current_state(TASK_INTERRUPTIBLE);
+                schedule();
                 if (kthread_should_stop())
                         break;
-                if (!rc)
-                        rebuild_lun_table(h, 0);
+
+                while (1) {
+                        mutex_lock(&scan_mutex);
+                        if (list_empty(&scan_q)) {
+                                mutex_unlock(&scan_mutex);
+                                break;
+                        }
+
+                        h = list_entry(scan_q.next,
+                                       struct ctlr_info,
+                                       scan_list);
+                        list_del(&h->scan_list);
+                        h->busy_scanning = 1;
+                        mutex_unlock(&scan_mutex);
+
+                        if (h) {
+                                rebuild_lun_table(h, 0);
+                                complete_all(&h->scan_wait);
+                                mutex_lock(&scan_mutex);
+                                h->busy_scanning = 0;
+                                mutex_unlock(&scan_mutex);
+                        }
+                }
         }
+
         return 0;
 }
 
@@ -3269,8 +3375,8 @@ static int check_for_unit_attention(ctlr_info_t *h, CommandList_struct *c)
         case REPORT_LUNS_CHANGED:
                 printk(KERN_WARNING "cciss%d: report LUN data "
                         "changed\n", h->ctlr);
-                if (h->rescan_wait)
-                        complete(h->rescan_wait);
+                add_to_scan_list(h);
+                wake_up_process(cciss_scan_thread);
                 return 1;
         break;
         case POWER_OR_RESET:
@@ -3919,6 +4025,7 @@ static int __devinit cciss_init_one(struct pci_dev *pdev,
         hba[i]->busy_initializing = 1;
         INIT_HLIST_HEAD(&hba[i]->cmpQ);
         INIT_HLIST_HEAD(&hba[i]->reqQ);
+        mutex_init(&hba[i]->busy_shutting_down);
 
         if (cciss_pci_init(hba[i], pdev) != 0)
                 goto clean0;
@@ -3927,6 +4034,8 @@ static int __devinit cciss_init_one(struct pci_dev *pdev,
         hba[i]->ctlr = i;
         hba[i]->pdev = pdev;
 
+        init_completion(&hba[i]->scan_wait);
+
         if (cciss_create_hba_sysfs_entry(hba[i]))
                 goto clean0;
 
@@ -4036,14 +4145,8 @@ static int __devinit cciss_init_one(struct pci_dev *pdev,
 
         hba[i]->cciss_max_sectors = 2048;
 
-        hba[i]->busy_initializing = 0;
-
         rebuild_lun_table(hba[i], 1);
-        hba[i]->cciss_scan_thread = kthread_run(scan_thread, hba[i],
-                                "cciss_scan%02d", i);
-        if (IS_ERR(hba[i]->cciss_scan_thread))
-                return PTR_ERR(hba[i]->cciss_scan_thread);
-
+        hba[i]->busy_initializing = 0;
         return 1;
 
 clean4:
@@ -4126,8 +4229,9 @@ static void __devexit cciss_remove_one(struct pci_dev *pdev)
                 return;
         }
 
-        kthread_stop(hba[i]->cciss_scan_thread);
+        mutex_lock(&hba[i]->busy_shutting_down);
 
+        remove_from_scan_list(hba[i]);
         remove_proc_entry(hba[i]->devname, proc_cciss);
         unregister_blkdev(hba[i]->major, hba[i]->devname);
 
@@ -4174,6 +4278,7 @@ static void __devexit cciss_remove_one(struct pci_dev *pdev)
         pci_release_regions(pdev);
         pci_set_drvdata(pdev, NULL);
         cciss_destroy_hba_sysfs_entry(hba[i]);
+        mutex_unlock(&hba[i]->busy_shutting_down);
         free_hba(i);
 }
 
@@ -4206,15 +4311,25 @@ static int __init cciss_init(void)
         if (err)
                 return err;
 
+        /* Start the scan thread */
+        cciss_scan_thread = kthread_run(scan_thread, NULL, "cciss_scan");
+        if (IS_ERR(cciss_scan_thread)) {
+                err = PTR_ERR(cciss_scan_thread);
+                goto err_bus_unregister;
+        }
+
         /* Register for our PCI devices */
         err = pci_register_driver(&cciss_pci_driver);
         if (err)
-                goto err_bus_register;
+                goto err_thread_stop;
 
         return 0;
 
-err_bus_register:
+err_thread_stop:
+        kthread_stop(cciss_scan_thread);
+err_bus_unregister:
         bus_unregister(&cciss_bus_type);
+
         return err;
 }
 
@@ -4231,6 +4346,7 @@ static void __exit cciss_cleanup(void)
                         cciss_remove_one(hba[i]->pdev);
                 }
         }
+        kthread_stop(cciss_scan_thread);
         remove_proc_entry("driver/cciss", NULL);
         bus_unregister(&cciss_bus_type);
 }