Drivers: hv: vmbus: avoid wait_for_completion() on crash

wait_for_completion() may sleep, it enables interrupts and this
is something we really want to avoid on crashes because interrupt
handlers can cause other crashes. Switch to the recently introduced
vmbus_wait_for_unload() doing busy wait instead.

Reported-by: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Radim Kr.má<rkrcmar@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index b40f429..f70e352 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -641,7 +641,7 @@
 	complete(&vmbus_connection.unload_event);
 }
 
-void vmbus_initiate_unload(void)
+void vmbus_initiate_unload(bool crash)
 {
 	struct vmbus_channel_message_header hdr;
 
@@ -658,7 +658,7 @@
 	 * vmbus_initiate_unload() is also called on crash and the crash can be
 	 * happening in an interrupt context, where scheduling is impossible.
 	 */
-	if (!in_interrupt())
+	if (!crash)
 		wait_for_completion(&vmbus_connection.unload_event);
 	else
 		vmbus_wait_for_unload();