allocate files in background

db/instance.cpp

@@ -30,6 +30,7 @@
 #include "reccache.h"
 #include "replset.h"
 #include "../s/d_logic.h"
+#include "../util/file_allocator.h"
 #if !defined(_WIN32)
 #include <sys/file.h>
 #endif
@@ -652,6 +653,11 @@ namespace mongo {
         /* must do this before unmapping mem or you may get a seg fault */
         closeAllSockets();
 
+        // wait until file preallocation finishes
+        // we would only hang here if the file_allocator code generates a
+        // synchronous signal, which we don't expect
+        theFileAllocator().waitUntilFinished();
+        
         stringstream ss3;
         MemoryMappedFile::closeAllFiles( ss3 );
         rawOut( ss3.str() );