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

/*

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