PM: Allow pm_runtime_suspend() to succeed during system suspend

The dpm_prepare() function increments the runtime PM reference
counters of all devices to prevent pm_runtime_suspend() from
executing subsystem-level callbacks.  However, this was supposed to
guard against a specific race condition that cannot happen, because
the power management workqueue is freezable, so pm_runtime_suspend()
can only be called synchronously during system suspend and we can
rely on subsystems and device drivers to avoid doing that
unnecessarily.

Make dpm_prepare() drop the runtime PM reference to each device
after making sure that runtime resume is not pending for it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Kevin Hilman <khilman@ti.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 83404973f97a..f7a755923751 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -669,7 +669,6 @@ static void dpm_complete(pm_message_t state)
                 mutex_unlock(&dpm_list_mtx);
 
                 device_complete(dev, state);
-                pm_runtime_put_sync(dev);
 
                 mutex_lock(&dpm_list_mtx);
                 put_device(dev);
@@ -1005,12 +1004,9 @@ static int dpm_prepare(pm_message_t state)
                 if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
                         pm_wakeup_event(dev, 0);
 
-                if (pm_wakeup_pending()) {
-                        pm_runtime_put_sync(dev);
-                        error = -EBUSY;
-                } else {
-                        error = device_prepare(dev, state);
-                }
+                pm_runtime_put_sync(dev);
+                error = pm_wakeup_pending() ?
+                                -EBUSY : device_prepare(dev, state);
 
                 mutex_lock(&dpm_list_mtx);
                 if (error) {