PM: Fix potential issue with failing asynchronous suspend

There is a potential issue with the asynchronous suspend code that
a device driver suspending asynchronously may not notice that it
should back off.  There are two failing scenarions, (1) when the
driver is waiting for a driver suspending synchronously to complete
and that second driver returns error code, in which case async_error
won't be set and the waiting driver will continue suspending and (2)
after the driver has called device_pm_wait_for_dev() and the waited
for driver returns error code, in which case the caller of
device_pm_wait_for_dev() will not know that there was an error and
will continue suspending.

To fix this issue make __device_suspend() set async_error, so
async_suspend() doesn't need to set it any more, and make
device_pm_wait_for_dev() return async_error, so that its callers
can check whether or not they should continue suspending.

No more changes are necessary, since device_pm_wait_for_dev() is
not used by any drivers' suspend routines.

Reported-by: Colin Cross <ccross@android.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 7ae6fe414c38..31b526661ec4 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -51,6 +51,8 @@ static pm_message_t pm_transition;
  */
 static bool transition_started;
 
+static int async_error;
+
 /**
  * device_pm_init - Initialize the PM-related part of a device object.
  * @dev: Device object being initialized.
@@ -602,6 +604,7 @@ static void dpm_resume(pm_message_t state)
         INIT_LIST_HEAD(&list);
         mutex_lock(&dpm_list_mtx);
         pm_transition = state;
+        async_error = 0;
 
         list_for_each_entry(dev, &dpm_list, power.entry) {
                 if (dev->power.status < DPM_OFF)
@@ -831,8 +834,6 @@ static int legacy_suspend(struct device *dev, pm_message_t state,
         return error;
 }
 
-static int async_error;
-
 /**
  * device_suspend - Execute "suspend" callbacks for given device.
  * @dev: Device to handle.
@@ -887,6 +888,9 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
         device_unlock(dev);
         complete_all(&dev->power.completion);
 
+        if (error)
+                async_error = error;
+
         return error;
 }
 
@@ -896,10 +900,8 @@ static void async_suspend(void *data, async_cookie_t cookie)
         int error;
 
         error = __device_suspend(dev, pm_transition, true);
-        if (error) {
+        if (error)
                 pm_dev_err(dev, pm_transition, " async", error);
-                async_error = error;
-        }
 
         put_device(dev);
 }
@@ -1087,8 +1089,9 @@ EXPORT_SYMBOL_GPL(__suspend_report_result);
  * @dev: Device to wait for.
  * @subordinate: Device that needs to wait for @dev.
  */
-void device_pm_wait_for_dev(struct device *subordinate, struct device *dev)
+int device_pm_wait_for_dev(struct device *subordinate, struct device *dev)
 {
         dpm_wait(dev, subordinate->power.async_suspend);
+        return async_error;
 }
 EXPORT_SYMBOL_GPL(device_pm_wait_for_dev);