PM-runtime: Fix __pm_runtime_set_status() race with runtime resume

Commit 4080ab08 ("PM-runtime: Take suppliers into account in
__pm_runtime_set_status()") introduced a race condition that may
trigger if __pm_runtime_set_status() is used incorrectly (that is,
if it is called when PM-runtime is enabled for the target device
and working).

In that case, if the original PM-runtime status of the device is
RPM_SUSPENDED, a runtime resume of the device may occur after
__pm_runtime_set_status() has dropped its power.lock spinlock
and before deactivating its suppliers, so the suppliers may be
deactivated while the device is PM-runtime-active which may lead
to functional issues.

To avoid that, modify __pm_runtime_set_status() to check whether
or not PM-runtime is enabled for the device before activating its
suppliers (if the new status is RPM_ACTIVE) and either return an
error if that's the case or increment the device's disable_depth
counter to prevent PM-runtime from being enabled for it while
the remaining part of the function is running (disable_depth is
then decremented on the way out).

Fixes: 4080ab08 ("PM-runtime: Take suppliers into account in __pm_runtime_set_status()")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/power/runtime.c

@@ -1106,6 +1106,22 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)
 	if (status != RPM_ACTIVE && status != RPM_SUSPENDED)
 		return -EINVAL;
 
+	spin_lock_irq(&dev->power.lock);
+
+	/*
+	 * Prevent PM-runtime from being enabled for the device or return an
+	 * error if it is enabled already and working.
+	 */
+	if (dev->power.runtime_error || dev->power.disable_depth)
+		dev->power.disable_depth++;
+	else
+		error = -EAGAIN;
+
+	spin_unlock_irq(&dev->power.lock);
+
+	if (error)
+		return error;
+
 	/*
 	 * If the new status is RPM_ACTIVE, the suppliers can be activated
 	 * upfront regardless of the current status, because next time
@@ -1124,12 +1140,6 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)
 
 	spin_lock_irq(&dev->power.lock);
 
-	if (!dev->power.runtime_error && !dev->power.disable_depth) {
-		status = dev->power.runtime_status;
-		error = -EAGAIN;
-		goto out;
-	}
-
 	if (dev->power.runtime_status == status || !parent)
 		goto out_set;
 
@@ -1182,6 +1192,8 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)
 		device_links_read_unlock(idx);
 	}
 
+	pm_runtime_enable(dev);
+
 	return error;
 }
 EXPORT_SYMBOL_GPL(__pm_runtime_set_status);