[Devel] Re: [PATCH] cpci_hotplug: Convert to use the kthread API

[Scott Murray]

On Fri, 4 May 2007, Christoph Hellwig wrote:

> On Fri, Apr 27, 2007 at 06:07:49PM -0400, Scott Murray wrote:
> > Sorry, it took me a few days to get to testing this out.  It looks good,    
> > but I had to make a couple of tweaks to avoid a hang when rmmod'ing a
> > board driver.  The board drivers do:
> > 
> > cpci_hp_stop()
> > cpci_hp_unregister_controller(controller)
> > 
> > to shutdown, and the check in cpci_hp_unregister_controller if the thread
> > is running wasn't working due to a bit too much code being excised.  The
> > result was kthread_stop being called twice, which hangs.  I've indicated 
> > my changes to avoid this inline below.
> 
> Can you forward the patches with your fix to Andrew to make sure he
> picks it up?

Andrew, here is my updated version of Christoph's kthread conversion 
patch for cpci_hotplug.  I've CC'ed Kristen so she won't be surprised
when this eventually goes to mainline.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Scott Murray <scottm at somanetworks.com>

---

diff --git a/drivers/pci/hotplug/cpci_hotplug_core.c b/drivers/pci/hotplug/cpci_hotplug_core.c
index 6845515..ed4d44e 100644
--- a/drivers/pci/hotplug/cpci_hotplug_core.c
+++ b/drivers/pci/hotplug/cpci_hotplug_core.c
@@ -35,6 +35,7 @@
 #include <linux/smp_lock.h>
 #include <asm/atomic.h>
 #include <linux/delay.h>
+#include <linux/kthread.h>
 #include "cpci_hotplug.h"
 
 #define DRIVER_AUTHOR	"Scott Murray <scottm at somanetworks.com>"
@@ -59,9 +60,8 @@ static int slots;
 static atomic_t extracting;
 int cpci_debug;
 static struct cpci_hp_controller *controller;
-static struct semaphore event_semaphore;	/* mutex for process loop (up if something to process) */
-static struct semaphore thread_exit;		/* guard ensure thread has exited before calling it quits */
-static int thread_finished = 1;
+static struct task_struct *cpci_thread;
+static int thread_finished;
 
 static int enable_slot(struct hotplug_slot *slot);
 static int disable_slot(struct hotplug_slot *slot);
@@ -357,9 +357,7 @@ cpci_hp_intr(int irq, void *data)
 	controller->ops->disable_irq();
 
 	/* Trigger processing by the event thread */
-	dbg("Signal event_semaphore");
-	up(&event_semaphore);
-	dbg("exited cpci_hp_intr");
+	wake_up_process(cpci_thread);
 	return IRQ_HANDLED;
 }
 
@@ -521,17 +519,12 @@ event_thread(void *data)
 {
 	int rc;
 
-	lock_kernel();
-	daemonize("cpci_hp_eventd");
-	unlock_kernel();
-
 	dbg("%s - event thread started", __FUNCTION__);
 	while (1) {
 		dbg("event thread sleeping");
-		down_interruptible(&event_semaphore);
-		dbg("event thread woken, thread_finished = %d",
-		    thread_finished);
-		if (thread_finished || signal_pending(current))
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule();
+		if (kthread_should_stop())
 			break;
 		do {
 			rc = check_slots();
@@ -541,18 +534,17 @@ event_thread(void *data)
 			} else if (rc < 0) {
 				dbg("%s - error checking slots", __FUNCTION__);
 				thread_finished = 1;
-				break;
+				goto out;
 			}
-		} while (atomic_read(&extracting) && !thread_finished);
-		if (thread_finished)
+		} while (atomic_read(&extracting) && !kthread_should_stop());
+		if (kthread_should_stop())
 			break;
 
 		/* Re-enable ENUM# interrupt */
 		dbg("%s - re-enabling irq", __FUNCTION__);
 		controller->ops->enable_irq();
 	}
-	dbg("%s - event thread signals exit", __FUNCTION__);
-	up(&thread_exit);
+ out:
 	return 0;
 }
 
@@ -562,12 +554,8 @@ poll_thread(void *data)
 {
 	int rc;
 
-	lock_kernel();
-	daemonize("cpci_hp_polld");
-	unlock_kernel();
-
 	while (1) {
-		if (thread_finished || signal_pending(current))
+		if (kthread_should_stop() || signal_pending(current))
 			break;
 		if (controller->ops->query_enum()) {
 			do {
@@ -578,48 +566,36 @@ poll_thread(void *data)
 				} else if (rc < 0) {
 					dbg("%s - error checking slots", __FUNCTION__);
 					thread_finished = 1;
-					break;
+					goto out;
 				}
-			} while (atomic_read(&extracting) && !thread_finished);
+			} while (atomic_read(&extracting) && !kthread_should_stop());
 		}
 		msleep(100);
 	}
-	dbg("poll thread signals exit");
-	up(&thread_exit);
+ out:
 	return 0;
 }
 
 static int
 cpci_start_thread(void)
 {
-	int pid;
-
-	/* initialize our semaphores */
-	init_MUTEX_LOCKED(&event_semaphore);
-	init_MUTEX_LOCKED(&thread_exit);
-	thread_finished = 0;
-
 	if (controller->irq)
-		pid = kernel_thread(event_thread, NULL, 0);
+		cpci_thread = kthread_run(event_thread, NULL, "cpci_hp_eventd");
 	else
-		pid = kernel_thread(poll_thread, NULL, 0);
-	if (pid < 0) {
+		cpci_thread = kthread_run(poll_thread, NULL, "cpci_hp_polld");
+	if (IS_ERR(cpci_thread)) {
 		err("Can't start up our thread");
-		return -1;
+		return PTR_ERR(cpci_thread);
 	}
-	dbg("Our thread pid = %d", pid);
+	thread_finished = 0;
 	return 0;
 }
 
 static void
 cpci_stop_thread(void)
 {
+	kthread_stop(cpci_thread);
 	thread_finished = 1;
-	dbg("thread finish command given");
-	if (controller->irq)
-		up(&event_semaphore);
-	dbg("wait for thread to exit");
-	down(&thread_exit);
 }
 
 int
 

-- 
Scott Murray
SOMA Networks, Inc.
Toronto, Ontario
e-mail: scottm at somanetworks.com
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