Drivers: hv: hv_balloon: Don't post pressure status from interrupt context

We currently release memory (balloon down) in the interrupt context and we also
post memory status while releasing memory. Rather than posting the status
in the interrupt context, wakeup the status posting thread to post the status.
This will address the inconsistent lock state that Sitsofe Wheeler <sitsofe@gmail.com>
reported:

http://lkml.iu.edu/hypermail/linux/kernel/1411.1/00075.html

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Sitsofe Wheeler <sitsofe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/hv_balloon.c

@@ -1226,7 +1226,7 @@ static void balloon_down(struct hv_dynmem_device *dm,
 
 	for (i = 0; i < range_count; i++) {
 		free_balloon_pages(dm, &range_array[i]);
-		post_status(&dm_device);
+		complete(&dm_device.config_event);
 	}
 
 	if (req->more_pages == 1)
@@ -1250,19 +1250,16 @@ static void balloon_onchannelcallback(void *context);
 static int dm_thread_func(void *dm_dev)
 {
 	struct hv_dynmem_device *dm = dm_dev;
-	int t;
 
 	while (!kthread_should_stop()) {
-		t = wait_for_completion_interruptible_timeout(
+		wait_for_completion_interruptible_timeout(
 						&dm_device.config_event, 1*HZ);
 		/*
 		 * The host expects us to post information on the memory
 		 * pressure every second.
 		 */
-
-		if (t == 0)
-			post_status(dm);
-
+		reinit_completion(&dm_device.config_event);
+		post_status(dm);
 	}
 
 	return 0;