[PATCH] PM: allow for usage_count > 0 in pm_runtime_get()

Alan Stern
2009-11-30T16:35:03Z

This patch (as1308) fixes __pm_runtime_get(). Currently the routine
will resume a device if the prior usage count was 0. But this isn't
right; thanks to pm_runtime_get_noresume() the usage count can be
positive even while the device is suspended.

Now the routine always tries to carry out a resume when called
synchronously. When called asynchronously, it avoids the overhead of
an unnecessary spinlock acquisition by doing the resume only if the
device's state was SUSPENDING or SUSPENDED.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

---

Index: usb-2.6/drivers/base/power/runtime.c
===================================================================
--- usb-2.6.orig/drivers/base/power/runtime.c
+++ usb-2.6/drivers/base/power/runtime.c
@@ -703,16 +703,22 @@ EXPORT_SYMBOL_GPL(pm_request_resume);
* @dev: Device to handle.
* @sync: If set and the device is suspended, resume it synchronously.
*
- * Increment the usage count of the device and if it was zero previously,
- * resume it or submit a resume request for it, depending on the value of @sync.
+ * Increment the usage count of the device. If @sync is set, resume the device
+ * and wait for the resume to complete. Otherwise if the device is currently
+ * suspending or suspended, submit a resume request.
+ *
+ * If @sync is clear, the caller is responsible for synchronization.
*/
int __pm_runtime_get(struct device *dev, bool sync)
{
- int retval = 1;
-
- if (atomic_add_return(1, &dev->power.usage_count) == 1)
- retval = sync ? pm_runtime_resume(dev) : pm_request_resume(dev);
+ int retval = 0;

+ atomic_inc(&dev->power.usage_count);
+ if (sync)
+ retval = pm_runtime_resume(dev);
+ else if (dev->power.runtime_status == RPM_SUSPENDING ||
+ dev->power.runtime_status == RPM_SUSPENDED)
+ retval = pm_request_resume(dev);
return retval;
}
EXPORT_SYMBOL_GPL(__pm_runtime_get);
Index: usb-2.6/Documentation/power/runtime_pm.txt
===================================================================
--- usb-2.6.orig/Documentation/power/runtime_pm.txt
+++ usb-2.6/Documentation/power/runtime_pm.txt
@@ -276,8 +276,9 @@ drivers/base/power/runtime.c and include
- increment the device's usage counter

int pm_runtime_get(struct device *dev);
- - increment the device's usage counter, run pm_request_resume(dev) and
- return its result
+ - increment the device's usage counter; if the device is currently
+ suspending or suspended then run pm_request_resume(dev) and return its
+ result

int pm_runtime_get_sync(struct device *dev);
- increment the device's usage counter, run pm_runtime_resume(dev) and