Async suspend-resume patch w/ completions (was: Re: Async suspend-resume patch w/ rwsems)

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday 09 December 2009, Alan Stern wrote:
> On Wed, 9 Dec 2009, Rafael J. Wysocki wrote:
> 
> > On Wednesday 09 December 2009, Alan Stern wrote:
> > > On Tue, 8 Dec 2009, Rafael J. Wysocki wrote:
> > > 
> > > > For completness, below is the full async suspend/resume patch with rwlocks,
> > > > that has been (very slightly) tested and doesn't seem to break things.
> > > > 
> > > > [Note to Alan: lockdep doesn't seem to complain about the not annotated nested
> > > > locks.]
> > > 
> > > I can't imagine why not.  And wouldn't lockdep get confused by the fact
> > > that in the async case, the rwsems are released by a different process
> > > from the one that acquired them?
> > 
> > /me looks at the .config
> > 
> > I have CONFIG_LOCKDEP_SUPPORT set, is there anything else I need to set
> > in .config?
> 
> How about CONFIG_PROVE_LOCKING?  If lockdep really does start 
> complaining then switching to completions would be a simple way to 
> appease it.

Ah, that one is not set.  I guess I'll try it later, although I've already
decided to use completions anyway.

...
> > > How about exporting a wait_for_device_to_resume() routine?  Drivers
> > > could call it for non-tree resume constraints:
> > > 
> > > 	void wait_for_device_to_resume(struct device *other)
> > > 	{
> > > 		down_read(&other->power.rwsem);
> > > 		up_read(&other->power.rwsem);
> > > 	}
> > > 
> > > Unfortunately there is no equivalent for non-tree suspend constraints.
> > 
> > If we use completions, it will be possible to just export something like
> > 
> > dpm_wait(dev)
> > {
> >         if (dev)
> >                 wait_for_completion(dev->power.completion);
> > }
> > 
> > I think.  It appears that will also work for suspend, unless I'm missing
> > something.
> 
> It will.

Completions it is, then.

Additionally, I've removed the async support from the _noirq parts and moved
the setting of power.status on suspend to __device_suspend().  The result is
appended.

Rafael


---
 drivers/base/power/main.c    |  124 ++++++++++++++++++++++++++++++++++++++++---
 include/linux/device.h       |    6 ++
 include/linux/pm.h           |   12 ++++
 include/linux/resume-trace.h |    7 ++
 4 files changed, 143 insertions(+), 6 deletions(-)

Index: linux-2.6/include/linux/pm.h
===================================================================
--- linux-2.6.orig/include/linux/pm.h
+++ linux-2.6/include/linux/pm.h
@@ -26,6 +26,7 @@
 #include <linux/spinlock.h>
 #include <linux/wait.h>
 #include <linux/timer.h>
+#include <linux/completion.h>
 
 /*
  * Callbacks for platform drivers to implement.
@@ -412,9 +413,11 @@ struct dev_pm_info {
 	pm_message_t		power_state;
 	unsigned int		can_wakeup:1;
 	unsigned int		should_wakeup:1;
+	unsigned		async_suspend:1;
 	enum dpm_state		status;		/* Owned by the PM core */
 #ifdef CONFIG_PM_SLEEP
 	struct list_head	entry;
+	struct completion	completion;
 #endif
 #ifdef CONFIG_PM_RUNTIME
 	struct timer_list	suspend_timer;
@@ -508,6 +511,13 @@ extern void __suspend_report_result(cons
 		__suspend_report_result(__func__, fn, ret);		\
 	} while (0)
 
+extern int __dpm_wait(struct device *dev, void *ign);
+
+static inline void dpm_wait(struct device *dev)
+{
+	__dpm_wait(dev, NULL);
+}
+
 #else /* !CONFIG_PM_SLEEP */
 
 #define device_pm_lock() do {} while (0)
@@ -520,6 +530,8 @@ static inline int dpm_suspend_start(pm_m
 
 #define suspend_report_result(fn, ret)		do {} while (0)
 
+static inline void dpm_wait(struct device *dev) {}
+
 #endif /* !CONFIG_PM_SLEEP */
 
 /* How to reorder dpm_list after device_move() */
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
@@ -25,6 +25,7 @@
 #include <linux/resume-trace.h>
 #include <linux/rwsem.h>
 #include <linux/interrupt.h>
+#include <linux/async.h>
 
 #include "../base.h"
 #include "power.h"
@@ -42,6 +43,7 @@
 LIST_HEAD(dpm_list);
 
 static DEFINE_MUTEX(dpm_list_mtx);
+static pm_message_t pm_transition;
 
 /*
  * Set once the preparation of devices for a PM transition has started, reset
@@ -56,6 +58,7 @@ static bool transition_started;
 void device_pm_init(struct device *dev)
 {
 	dev->power.status = DPM_ON;
+	init_completion(&dev->power.completion);
 	pm_runtime_init(dev);
 }
 
@@ -162,6 +165,39 @@ void device_pm_move_last(struct device *
 }
 
 /**
+ * __dpm_wait - Wait for a PM operation to complete.
+ * @dev: Device to wait for.
+ * @ign: This value is not used by the function.
+ */
+int __dpm_wait(struct device *dev, void *ign)
+{
+	if (dev)
+		wait_for_completion(&dev->power.completion);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__dpm_wait);
+
+static void dpm_wait_for_children(struct device *dev)
+{
+       device_for_each_child(dev, NULL, __dpm_wait);
+}
+
+/**
+ * dpm_synchronize - Wait for PM callbacks of all devices to complete.
+ */
+static void dpm_synchronize(void)
+{
+	struct device *dev;
+
+	async_synchronize_full();
+
+	mutex_lock(&dpm_list_mtx);
+	list_for_each_entry(dev, &dpm_list, power.entry)
+		INIT_COMPLETION(dev->power.completion);
+	mutex_unlock(&dpm_list_mtx);
+}
+
+/**
  * pm_op - Execute the PM operation appropriate for given PM event.
  * @dev: Device to handle.
  * @ops: PM operations to choose from.
@@ -381,17 +417,18 @@ void dpm_resume_noirq(pm_message_t state
 EXPORT_SYMBOL_GPL(dpm_resume_noirq);
 
 /**
- * device_resume - Execute "resume" callbacks for given device.
+ * __device_resume - Execute "resume" callbacks for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
  */
-static int device_resume(struct device *dev, pm_message_t state)
+static int __device_resume(struct device *dev, pm_message_t state)
 {
 	int error = 0;
 
 	TRACE_DEVICE(dev);
 	TRACE_RESUME(0);
 
+	dpm_wait(dev->parent);
 	down(&dev->sem);
 
 	if (dev->bus) {
@@ -426,11 +463,34 @@ static int device_resume(struct device *
 	}
  End:
 	up(&dev->sem);
+	complete_all(&dev->power.completion);
 
 	TRACE_RESUME(error);
 	return error;
 }
 
+static void async_resume(void *data, async_cookie_t cookie)
+{
+	struct device *dev = (struct device *)data;
+	int error;
+
+	error = __device_resume(dev, pm_transition);
+	if (error)
+		pm_dev_err(dev, pm_transition, " async", error);
+	put_device(dev);
+}
+
+static int device_resume(struct device *dev)
+{
+	if (dev->power.async_suspend && !pm_trace_is_enabled()) {
+		get_device(dev);
+		async_schedule(async_resume, dev);
+		return 0;
+	}
+
+	return __device_resume(dev, pm_transition);
+}
+
 /**
  * dpm_resume - Execute "resume" callbacks for non-sysdev devices.
  * @state: PM transition of the system being carried out.
@@ -444,6 +504,7 @@ static void dpm_resume(pm_message_t stat
 
 	INIT_LIST_HEAD(&list);
 	mutex_lock(&dpm_list_mtx);
+	pm_transition = state;
 	while (!list_empty(&dpm_list)) {
 		struct device *dev = to_device(dpm_list.next);
 
@@ -454,7 +515,7 @@ static void dpm_resume(pm_message_t stat
 			dev->power.status = DPM_RESUMING;
 			mutex_unlock(&dpm_list_mtx);
 
-			error = device_resume(dev, state);
+			error = device_resume(dev);
 
 			mutex_lock(&dpm_list_mtx);
 			if (error)
@@ -469,6 +530,7 @@ static void dpm_resume(pm_message_t stat
 	}
 	list_splice(&list, &dpm_list);
 	mutex_unlock(&dpm_list_mtx);
+	dpm_synchronize();
 }
 
 /**
@@ -533,6 +595,8 @@ static void dpm_complete(pm_message_t st
 	mutex_unlock(&dpm_list_mtx);
 }
 
+static atomic_t async_error;
+
 /**
  * dpm_resume_end - Execute "resume" callbacks and complete system transition.
  * @state: PM transition of the system being carried out.
@@ -628,10 +692,11 @@ EXPORT_SYMBOL_GPL(dpm_suspend_noirq);
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
  */
-static int device_suspend(struct device *dev, pm_message_t state)
+static int __device_suspend(struct device *dev, pm_message_t state)
 {
 	int error = 0;
 
+	dpm_wait_for_children(dev);
 	down(&dev->sem);
 
 	if (dev->class) {
@@ -666,12 +731,50 @@ static int device_suspend(struct device 
 			suspend_report_result(dev->bus->suspend, error);
 		}
 	}
+
+	if (!error)
+		dev->power.status = DPM_OFF;
+
  End:
 	up(&dev->sem);
+	complete_all(&dev->power.completion);
 
 	return error;
 }
 
+static void async_suspend(void *data, async_cookie_t cookie)
+{
+	struct device *dev = (struct device *)data;
+	int error = atomic_read(&async_error);
+
+	if (error) {
+		complete_all(&dev->power.completion);
+		goto End;
+	}
+
+	error = __device_suspend(dev, pm_transition);
+	if (error) {
+		pm_dev_err(dev, pm_transition, " async", error);
+		atomic_set(&async_error, error);
+	}
+
+ End:
+	put_device(dev);
+}
+
+static int device_suspend(struct device *dev, pm_message_t state)
+{
+	int error;
+
+	if (dev->power.async_suspend) {
+		get_device(dev);
+		async_schedule(async_suspend, dev);
+		return 0;
+	}
+
+	return __device_suspend(dev, pm_transition);
+}
+
 /**
  * dpm_suspend - Execute "suspend" callbacks for all non-sysdev devices.
  * @state: PM transition of the system being carried out.
@@ -683,6 +786,7 @@ static int dpm_suspend(pm_message_t stat
 
 	INIT_LIST_HEAD(&list);
 	mutex_lock(&dpm_list_mtx);
+	pm_transition = state;
 	while (!list_empty(&dpm_list)) {
 		struct device *dev = to_device(dpm_list.prev);
 
@@ -697,13 +801,18 @@ static int dpm_suspend(pm_message_t stat
 			put_device(dev);
 			break;
 		}
-		dev->power.status = DPM_OFF;
 		if (!list_empty(&dev->power.entry))
 			list_move(&dev->power.entry, &list);
 		put_device(dev);
+		error = atomic_read(&async_error);
+		if (error)
+			break;
 	}
 	list_splice(&list, dpm_list.prev);
 	mutex_unlock(&dpm_list_mtx);
+	dpm_synchronize();
+	if (!error)
+		error = atomic_read(&async_error);
 	return error;
 }
 
@@ -762,6 +871,7 @@ static int dpm_prepare(pm_message_t stat
 	INIT_LIST_HEAD(&list);
 	mutex_lock(&dpm_list_mtx);
 	transition_started = true;
+	atomic_set(&async_error, 0);
 	while (!list_empty(&dpm_list)) {
 		struct device *dev = to_device(dpm_list.next);
 
@@ -793,8 +903,10 @@ static int dpm_prepare(pm_message_t stat
 			break;
 		}
 		dev->power.status = DPM_SUSPENDING;
-		if (!list_empty(&dev->power.entry))
+		if (!list_empty(&dev->power.entry)) {
 			list_move_tail(&dev->power.entry, &list);
+			INIT_COMPLETION(dev->power.completion);
+		}
 		put_device(dev);
 	}
 	list_splice(&list, &dpm_list);
Index: linux-2.6/include/linux/resume-trace.h
===================================================================
--- linux-2.6.orig/include/linux/resume-trace.h
+++ linux-2.6/include/linux/resume-trace.h
@@ -6,6 +6,11 @@
 
 extern int pm_trace_enabled;
 
+static inline int pm_trace_is_enabled(void)
+{
+       return pm_trace_enabled;
+}
+
 struct device;
 extern void set_trace_device(struct device *);
 extern void generate_resume_trace(const void *tracedata, unsigned int user);
@@ -17,6 +22,8 @@ extern void generate_resume_trace(const 
 
 #else
 
+static inline int pm_trace_is_enabled(void) { return 0; }
+
 #define TRACE_DEVICE(dev) do { } while (0)
 #define TRACE_RESUME(dev) do { } while (0)
 
Index: linux-2.6/include/linux/device.h
===================================================================
--- linux-2.6.orig/include/linux/device.h
+++ linux-2.6/include/linux/device.h
@@ -472,6 +472,12 @@ static inline int device_is_registered(s
 	return dev->kobj.state_in_sysfs;
 }
 
+static inline void device_enable_async_suspend(struct device *dev, bool enable)
+{
+	if (dev->power.status == DPM_ON)
+		dev->power.async_suspend = enable;
+}
+
 void driver_init(void);
 
 /*