[PATCH 1/3] driver core: Support asynchronous driver shutdown

[Tanjore Suresh <tansuresh@google.com>]

This changes the bus driver interface to take in a flag to indicate
whether a bus and associated devices are willing to participate in
the asynchronous shutdown. If this flag is not set bus driver
implementation will follow synchronous shutdown semantics.

Signed-off-by: Tanjore Suresh <tansuresh@google.com>
---
 drivers/base/core.c        | 39 +++++++++++++++++++++++++++++++++++++-
 include/linux/device/bus.h | 10 ++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 3d6430eb0c6a..359e7067e8b8 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4479,6 +4479,7 @@ EXPORT_SYMBOL_GPL(device_change_owner);
 void device_shutdown(void)
 {
 	struct device *dev, *parent;
+	LIST_HEAD(async_shutdown_list);
 
 	wait_for_device_probe();
 	device_block_probing();
@@ -4523,7 +4524,14 @@ void device_shutdown(void)
 				dev_info(dev, "shutdown_pre\n");
 			dev->class->shutdown_pre(dev);
 		}
-		if (dev->bus && dev->bus->shutdown) {
+
+		if (dev->bus && dev->bus->shutdown_pre) {
+			if (initcall_debug)
+				dev_info(dev, "shutdown_pre\n");
+			dev->bus->shutdown_pre(dev);
+			list_add(&dev->kobj.entry,
+				&async_shutdown_list);
+		} else if (dev->bus && dev->bus->shutdown) {
 			if (initcall_debug)
 				dev_info(dev, "shutdown\n");
 			dev->bus->shutdown(dev);
@@ -4543,6 +4551,35 @@ void device_shutdown(void)
 		spin_lock(&devices_kset->list_lock);
 	}
 	spin_unlock(&devices_kset->list_lock);
+
+	/*
+	 * Second pass spin for only devices, that have configured
+	 * Asynchronous shutdown.
+	 */
+	while (!list_empty(&async_shutdown_list)) {
+		dev = list_entry(async_shutdown_list.next, struct device,
+				kobj.entry);
+		parent = get_device(dev->parent);
+		get_device(dev);
+		/*
+		 * Make sure the device is off the  list
+		 */
+		list_del_init(&dev->kobj.entry);
+		if (parent)
+			device_lock(parent);
+		device_lock(dev);
+		if (dev->bus && dev->bus->shutdown_post) {
+			if (initcall_debug)
+				dev_info(dev,
+				"shutdown_post called\n");
+			dev->bus->shutdown_post(dev);
+		}
+		device_unlock(dev);
+		if (parent)
+			device_unlock(parent);
+		put_device(dev);
+		put_device(parent);
+	}
 }
 
 /*
diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
index a039ab809753..e261819601e9 100644
--- a/include/linux/device/bus.h
+++ b/include/linux/device/bus.h
@@ -49,6 +49,14 @@ struct fwnode_handle;
  *		will never get called until they do.
  * @remove:	Called when a device removed from this bus.
  * @shutdown:	Called at shut-down time to quiesce the device.
+ * @shutdown_pre:	Called at the shutdown-time to start the shutdown
+ *			process on the device. This entry point will be called
+ *			only when the bus driver has indicated it would like
+ *			to participate in asynchronous shutdown completion.
+ * @shutdown_post:	Called at shutdown-time  to complete the shutdown
+ *			process of the device. This entry point will be called
+ *			only when the bus drive has indicated it would like to
+ *			participate in the asynchronous shutdown completion.
  *
  * @online:	Called to put the device back online (after offlining it).
  * @offline:	Called to put the device offline for hot-removal. May fail.
@@ -93,6 +101,8 @@ struct bus_type {
 	void (*sync_state)(struct device *dev);
 	void (*remove)(struct device *dev);
 	void (*shutdown)(struct device *dev);
+	void (*shutdown_pre)(struct device *dev);
+	void (*shutdown_post)(struct device *dev);
 
 	int (*online)(struct device *dev);
 	int (*offline)(struct device *dev);
-- 
2.35.1.1021.g381101b075-goog