[PATCH] mmc: use own work queue

The MMC layer uses the standard work queue for doing card detection.  As this
queue is shared with other crucial subsystems, the effects of a long (and
perhaps buggy) detection can cause the system to be unusable.  E.g.  the
keyboard stops working while the detection routine is running.

The solution is to add a specific mmc work queue to run the detection code in.
This is similar to how other subsystems handle detection (a full kernel
thread is the most common theme).
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/mmc/mmc.c

@@ -1166,9 +1166,9 @@ static void mmc_setup(struct mmc_host *host)
 void mmc_detect_change(struct mmc_host *host, unsigned long delay)
 {
 	if (delay)
-		schedule_delayed_work(&host->detect, delay);
+		mmc_schedule_delayed_work(&host->detect, delay);
 	else
-		schedule_work(&host->detect);
+		mmc_schedule_work(&host->detect);
 }
 
 EXPORT_SYMBOL(mmc_detect_change);
@@ -1311,7 +1311,7 @@ EXPORT_SYMBOL(mmc_remove_host);
  */
 void mmc_free_host(struct mmc_host *host)
 {
-	flush_scheduled_work();
+	mmc_flush_scheduled_work();
 	mmc_free_host_sysfs(host);
 }
 

drivers/mmc/mmc.h

@@ -18,4 +18,8 @@ struct mmc_host *mmc_alloc_host_sysfs(int extra, struct device *dev);
 int mmc_add_host_sysfs(struct mmc_host *host);
 void mmc_remove_host_sysfs(struct mmc_host *host);
 void mmc_free_host_sysfs(struct mmc_host *host);
+
+int mmc_schedule_work(struct work_struct *work);
+int mmc_schedule_delayed_work(struct work_struct *work, unsigned long delay);
+void mmc_flush_scheduled_work(void);
 #endif

drivers/mmc/mmc_sysfs.c

@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/device.h>
 #include <linux/idr.h>
+#include <linux/workqueue.h>
 
 #include <linux/mmc/card.h>
 #include <linux/mmc/host.h>
@@ -317,10 +318,41 @@ void mmc_free_host_sysfs(struct mmc_host *host)
 	class_device_put(&host->class_dev);
 }
 
+static struct workqueue_struct *workqueue;
+
+/*
+ * Internal function. Schedule work in the MMC work queue.
+ */
+int mmc_schedule_work(struct work_struct *work)
+{
+	return queue_work(workqueue, work);
+}
+
+/*
+ * Internal function. Schedule delayed work in the MMC work queue.
+ */
+int mmc_schedule_delayed_work(struct work_struct *work, unsigned long delay)
+{
+	return queue_delayed_work(workqueue, work, delay);
+}
+
+/*
+ * Internal function. Flush all scheduled work from the MMC work queue.
+ */
+void mmc_flush_scheduled_work(void)
+{
+	flush_workqueue(workqueue);
+}
 
 static int __init mmc_init(void)
 {
-	int ret = bus_register(&mmc_bus_type);
+	int ret;
+
+	workqueue = create_singlethread_workqueue("kmmcd");
+	if (!workqueue)
+		return -ENOMEM;
+
+	ret = bus_register(&mmc_bus_type);
 	if (ret == 0) {
 		ret = class_register(&mmc_host_class);
 		if (ret)
@@ -333,6 +365,7 @@ static void __exit mmc_exit(void)
 {
 	class_unregister(&mmc_host_class);
 	bus_unregister(&mmc_bus_type);
+	destroy_workqueue(workqueue);
 }
 
 module_init(mmc_init);