Re: [PATCH 1/4] PM: Introduce destroy_suspended_device()

[Rafael J. Wysocki]

On Wednesday, 2 of January 2008, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@xxxxxxx>
> 
> It sometimes is necessary to destroy a device object during a suspend or
> hibernation, but the PM core is supposed to control all device objects in that
> cases.  For this reason, it is necessary to introduce a mechanism allowing one
> to ask the PM core to remove a device object corresponding to a suspended
> device on one's behalf.
> 
> Define function destroy_suspended_device() that will schedule the removal of
> a device object corresponding to a suspended device by the PM core during the
> subsequent resume.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>

Sorry, a small fix is needed for this patch.  Namely, dpm_sysfs_remove(dev)
should not be called by device_pm_schedule_removal(), because it will be called
anyway from device_pm_remove() when the device object is finally unregistered
(we're talking here about unlikely error paths only, but still).

Corrected patch follows.

Thanks,
Rafael

---
From: Rafael J. Wysocki <rjw@xxxxxxx>

It sometimes is necessary to destroy a device object during a suspend or
hibernation, but the PM core is supposed to control all device objects in that
cases.  For this reason, it is necessary to introduce a mechanism allowing one
to ask the PM core to remove a device object corresponding to a suspended
device on one's behalf.

Define function destroy_suspended_device() that will schedule the removal of
a device object corresponding to a suspended device by the PM core during the
subsequent resume.

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
 drivers/base/core.c        |   44 +++++++++++++++++++++++++++++++++++++++-----
 drivers/base/power/main.c  |   35 ++++++++++++++++++++++++++---------
 drivers/base/power/power.h |    1 +
 include/linux/device.h     |    8 ++++++++
 4 files changed, 74 insertions(+), 14 deletions(-)

Index: linux-2.6/drivers/base/core.c
===================================================================
--- linux-2.6.orig/drivers/base/core.c
+++ linux-2.6/drivers/base/core.c
@@ -1156,14 +1156,11 @@ error:
 EXPORT_SYMBOL_GPL(device_create);
 
 /**
- * device_destroy - removes a device that was created with device_create()
+ * find_device - finds a device that was created with device_create()
  * @class: pointer to the struct class that this device was registered with
  * @devt: the dev_t of the device that was previously registered
- *
- * This call unregisters and cleans up a device that was created with a
- * call to device_create().
  */
-void device_destroy(struct class *class, dev_t devt)
+static struct device *find_device(struct class *class, dev_t devt)
 {
 	struct device *dev = NULL;
 	struct device *dev_tmp;
@@ -1176,12 +1173,49 @@ void device_destroy(struct class *class,
 		}
 	}
 	up(&class->sem);
+	return dev;
+}
 
+/**
+ * device_destroy - removes a device that was created with device_create()
+ * @class: pointer to the struct class that this device was registered with
+ * @devt: the dev_t of the device that was previously registered
+ *
+ * This call unregisters and cleans up a device that was created with a
+ * call to device_create().
+ */
+void device_destroy(struct class *class, dev_t devt)
+{
+	struct device *dev;
+
+	dev = find_device(class, devt);
 	if (dev)
 		device_unregister(dev);
 }
 EXPORT_SYMBOL_GPL(device_destroy);
 
+#ifdef CONFIG_PM_SLEEP
+/**
+ * destroy_suspended_device - schedules the removal of a suspended device
+ * @class: pointer to the struct class that this device was registered with
+ * @devt: the dev_t of the device that was previously registered
+ *
+ * This call notifies the PM core of the necessity to unregister a suspended
+ * device created with a call to device_create() (devices cannot be
+ * unregistered directly while suspended, since the PM core controls them in
+ * that cases).
+ */
+void destroy_suspended_device(struct class *class, dev_t devt)
+{
+	struct device *dev;
+
+	dev = find_device(class, devt);
+	if (dev)
+		device_pm_schedule_removal(dev);
+}
+EXPORT_SYMBOL_GPL(destroy_suspended_device);
+#endif /* CONFIG_PM_SLEEP */
+
 /**
  * device_rename - renames a device
  * @dev: the pointer to the struct device to be renamed
Index: linux-2.6/include/linux/device.h
===================================================================
--- linux-2.6.orig/include/linux/device.h
+++ linux-2.6/include/linux/device.h
@@ -521,6 +521,14 @@ extern struct device *device_create(stru
 				    dev_t devt, const char *fmt, ...)
 				    __attribute__((format(printf,4,5)));
 extern void device_destroy(struct class *cls, dev_t devt);
+#ifdef CONFIG_PM_SLEEP
+extern void destroy_suspended_device(struct class *cls, dev_t devt);
+#else /* !CONFIG_PM_SLEEP */
+static inline void destroy_suspended_device(struct class *cls, dev_t devt)
+{
+	device_destroy(cls, devt);
+}
+#endif /* !CONFIG_PM_SLEEP */
 
 /*
  * Platform "fixup" functions - allow the platform to have their say
Index: linux-2.6/drivers/base/power/power.h
===================================================================
--- linux-2.6.orig/drivers/base/power/power.h
+++ linux-2.6/drivers/base/power/power.h
@@ -20,6 +20,7 @@ static inline struct device *to_device(s
 
 extern void device_pm_add(struct device *);
 extern void device_pm_remove(struct device *);
+extern void device_pm_schedule_removal(struct device *);
 
 #else /* CONFIG_PM_SLEEP */
 
Index: linux-2.6/drivers/base/power/main.c
===================================================================
--- linux-2.6.orig/drivers/base/power/main.c
+++ linux-2.6/drivers/base/power/main.c
@@ -31,6 +31,7 @@
 LIST_HEAD(dpm_active);
 static LIST_HEAD(dpm_off);
 static LIST_HEAD(dpm_off_irq);
+static LIST_HEAD(dpm_destroy);
 
 static DEFINE_MUTEX(dpm_mtx);
 static DEFINE_MUTEX(dpm_list_mtx);
@@ -59,6 +60,16 @@ void device_pm_remove(struct device *dev
 	mutex_unlock(&dpm_list_mtx);
 }
 
+void device_pm_schedule_removal(struct device *dev)
+{
+	pr_debug("PM: Removing info for %s:%s\n",
+		 dev->bus ? dev->bus->name : "No Bus",
+		 kobject_name(&dev->kobj));
+	mutex_lock(&dpm_list_mtx);
+	list_move_tail(&dev->power.entry, &dpm_destroy);
+	mutex_unlock(&dpm_list_mtx);
+}
+
 
 /*------------------------- Resume routines -------------------------*/
 
@@ -113,11 +124,14 @@ static int resume_device_early(struct de
 	return error;
 }
 
-/*
- * Resume the devices that have either not gone through
- * the late suspend, or that did go through it but also
- * went through the early resume
+/**
+ *	dpm_resume - Restore state of each device in system.
+ *
+ *	Walk the dpm_off list, remove each entry, resume the device,
+ *	then add it to the dpm_active list.  Unregister devices scheduled for
+ *	removal.
  */
+
 static void dpm_resume(void)
 {
 	mutex_lock(&dpm_list_mtx);
@@ -134,14 +148,17 @@ static void dpm_resume(void)
 		put_device(dev);
 	}
 	mutex_unlock(&dpm_list_mtx);
-}
+	/* Unregister devices scheduled for removal */
+	while (!list_empty(&dpm_destroy)) {
+		struct list_head *entry = dpm_destroy.next;
+		struct device *dev = to_device(entry);
 
+		device_unregister(dev);
+	}
+}
 
 /**
- *	device_resume - Restore state of each device in system.
- *
- *	Walk the dpm_off list, remove each entry, resume the device,
- *	then add it to the dpm_active list.
+ *	device_resume - Invoke dpm_resume() under dpm_mtx.
  */
 
 void device_resume(void)
--
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