[RFC][PATCH 1/3] PM / sleep: Move runtime PM barrier invocation to device_prepare()

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Move the invocation of the runtime PM barrier during system suspend
(or hibernation) from __device_suspend() to device_prepare() to make
all runtime PM transitions in progress complete before executing
->prepare() callbacks for devices.

That will allow those callbacks to check if devices are runtime
suspended in a non-racy way.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/base/power/main.c |   31 +++++++++++++------------------
 1 file changed, 13 insertions(+), 18 deletions(-)

Index: linux-pm/drivers/base/power/main.c
===================================================================
--- linux-pm.orig/drivers/base/power/main.c
+++ linux-pm/drivers/base/power/main.c
@@ -1312,24 +1312,7 @@ static int __device_suspend(struct devic
 
 	dpm_wait_for_children(dev, async);
 
-	if (async_error)
-		goto Complete;
-
-	/*
-	 * If a device configured to wake up the system from sleep states
-	 * has been suspended at run time and there's a resume request pending
-	 * for it, this is equivalent to the device signaling wakeup, so the
-	 * system suspend operation should be aborted.
-	 */
-	if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
-		pm_wakeup_event(dev, 0);
-
-	if (pm_wakeup_pending()) {
-		async_error = -EBUSY;
-		goto Complete;
-	}
-
-	if (dev->power.syscore)
+	if (async_error || dev->power.syscore)
 		goto Complete;
 
 	dpm_watchdog_set(&wd, dev);
@@ -1500,6 +1483,18 @@ static int device_prepare(struct device
 	 */
 	pm_runtime_get_noresume(dev);
 
+	/*
+	 * If a device configured to wake up the system from sleep states
+	 * has been suspended at run time and there's a resume request pending
+	 * for it, this is equivalent to the device signaling wakeup, so the
+	 * system suspend operation should be aborted.
+	 */
+	if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
+		pm_wakeup_event(dev, 0);
+
+	if (pm_wakeup_pending())
+		return -EBUSY;
+
 	device_lock(dev);
 
 	dev->power.wakeup_path = device_may_wakeup(dev);