cciss: use only one scan thread
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.
Acked-by: Mike Miller <mike.miller@xxxxxx>
Signed-off-by: Andrew Patterson <andrew.patterson@xxxxxx>
---
diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 970c896..c6bba77 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -39,6 +39,7 @@
#include <linux/hdreg.h>
#include <linux/spinlock.h>
#include <linux/compat.h>
+#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <asm/io.h>
@@ -155,6 +156,10 @@ static struct board_type products[] = {
static ctlr_info_t *hba[MAX_CTLR];
+static struct task_struct *cciss_scan_thread;
+static struct mutex scan_mutex;
+static struct 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);
@@ -189,6 +194,8 @@ static int sendcmd_withirq_core(ctlr_info_t *h, CommandList_struct *c,
static int process_sendcmd_error(ctlr_info_t *h, CommandList_struct *c);
static void fail_all_cmds(unsigned long ctlr);
+static int add_to_scan_list(struct ctlr_info *h);
+static void remove_from_scan_list(struct ctlr_info *h);
static int scan_thread(void *data);
static int check_for_unit_attention(ctlr_info_t *h, CommandList_struct *c);
@@ -3232,20 +3239,121 @@ static irqreturn_t do_cciss_intr(int irq, void *dev_id)
return IRQ_HANDLED;
}
-static int scan_thread(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)
{
- ctlr_info_t *h = data;
- int rc;
- DECLARE_COMPLETION_ONSTACK(wait);
- h->rescan_wait = &wait;
+ 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;
- for (;;) {
- rc = wait_for_completion_interruptible(&wait);
- if (kthread_should_stop())
+ mutex_lock(&scan_mutex);
+ list_for_each_entry(test_h, &scan_q, scan_list) {
+ if (test_h == h) {
+ found = 1;
break;
- if (!rc)
+ }
+ }
+ 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)
+{
+ struct ctlr_info *h;
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ while (!kthread_should_stop()) {
+ mutex_lock(&scan_mutex);
+ if (list_empty(&scan_q)) {
+ h = NULL;
+ } else {
+ 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) {
+ __set_current_state(TASK_RUNNING);
rebuild_lun_table(h, 0);
+ complete_all(&h->scan_wait);
+ mutex_lock(&scan_mutex);
+ h->busy_scanning = 0;
+ mutex_unlock(&scan_mutex);
+ set_current_state(TASK_INTERRUPTIBLE);
+ } else {
+ schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
+ continue;
+ }
}
+
+ __set_current_state(TASK_RUNNING);
return 0;
}
@@ -3268,8 +3376,8 @@ 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:
@@ -3918,6 +4026,7 @@ 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;
@@ -3926,6 +4035,8 @@ 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;
@@ -4037,10 +4148,6 @@ static int __devinit cciss_init_one(struct pci_dev *pdev,
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);
return 1;
@@ -4125,8 +4232,9 @@ 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);
@@ -4173,6 +4281,7 @@ 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);
}
@@ -4205,15 +4314,27 @@ static int __init cciss_init(void)
if (err)
return err;
+ /* Start the scan thread */
+ mutex_init(&scan_mutex);
+ INIT_LIST_HEAD(&scan_q);
+ 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;
}
@@ -4230,6 +4351,7 @@ 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);
}
diff --git a/drivers/block/cciss.h b/drivers/block/cciss.h
index 06a5db2..859e0e0 100644
--- a/drivers/block/cciss.h
+++ b/drivers/block/cciss.h
@@ -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;
};
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