cciss: Use one scan thread per controller and fix hang during rmmod
Andrew Patterson [Thu, 17 Sep 2009 18:46:58 +0000 (13:46 -0500)]
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>

drivers/block/cciss.c
drivers/block/cciss.h

index f162f96..4fb63b8 100644 (file)
@@ -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);
 }
index 06a5db2..4fb3639 100644 (file)
@@ -2,6 +2,7 @@
 #define CCISS_H
 
 #include <linux/genhd.h>
+#include <linux/mutex.h>
 
 #include "cciss_cmd.h"
 
@@ -108,6 +109,8 @@ struct ctlr_info
        int                     nr_frees; 
        int                     busy_configuring;
        int                     busy_initializing;
+       int                     busy_scanning;
+       struct mutex            busy_shutting_down;
 
        /* This element holds the zero based queue number of the last
         * queue to be started.  It is used for fairness.
@@ -122,8 +125,8 @@ struct ctlr_info
        /* and saved for later processing */
 #endif
        unsigned char alive;
-       struct completion *rescan_wait;
-       struct task_struct *cciss_scan_thread;
+       struct list_head scan_list;
+       struct completion scan_wait;
        struct device dev;
 };