We may abort the process of detaching threads with multiple SIGINTs - which are
being sent during a testcase terminating its child GDB.

Some of the threads may not be properly PTRACE_DETACHed which hurts if they
should have been detached with SIGSTOP (as they are accidentally left running
on the debugger termination).

Index: gdb-7.9.50.20150520/gdb/defs.h
===================================================================
--- gdb-7.9.50.20150520.orig/gdb/defs.h	2015-05-31 18:06:24.579002757 +0200
+++ gdb-7.9.50.20150520/gdb/defs.h	2015-05-31 18:06:29.253031613 +0200
@@ -145,6 +145,7 @@ extern void set_quit_flag (void);
 /* Flag that function quit should call quit_force.  */
 extern volatile int sync_quit_force_run;
 
+extern int quit_flag_cleanup;
 extern int immediate_quit;
 
 extern void quit (void);
Index: gdb-7.9.50.20150520/gdb/top.c
===================================================================
--- gdb-7.9.50.20150520.orig/gdb/top.c	2015-05-31 18:06:24.580002763 +0200
+++ gdb-7.9.50.20150520/gdb/top.c	2015-05-31 18:06:29.254031619 +0200
@@ -1463,7 +1463,9 @@ quit_force (char *args, int from_tty)
   qt.args = args;
   qt.from_tty = from_tty;
 
-  /* We want to handle any quit errors and exit regardless.  */
+  /* We want to handle any quit errors and exit regardless but we should never
+     get user-interrupted to properly detach the inferior.  */
+  quit_flag_cleanup = 1;
 
   /* Get out of tfind mode, and kill or detach all inferiors.  */
   TRY
Index: gdb-7.9.50.20150520/gdb/utils.c
===================================================================
--- gdb-7.9.50.20150520.orig/gdb/utils.c	2015-05-31 18:06:24.582002776 +0200
+++ gdb-7.9.50.20150520/gdb/utils.c	2015-05-31 18:06:29.255031625 +0200
@@ -122,6 +122,11 @@ int job_control;
 
 int immediate_quit;
 
+/* Nonzero means we are already processing the quitting cleanups and we should
+   no longer get aborted.  */
+
+int quit_flag_cleanup;
+
 /* Nonzero means that strings with character values >0x7F should be printed
    as octal escapes.  Zero means just print the value (e.g. it's an
    international character, and the terminal or window can cope.)  */
Index: gdb-7.9.50.20150520/gdb/extension.c
===================================================================
--- gdb-7.9.50.20150520.orig/gdb/extension.c	2015-05-31 18:06:24.582002776 +0200
+++ gdb-7.9.50.20150520/gdb/extension.c	2015-05-31 18:06:29.256031632 +0200
@@ -833,6 +833,9 @@ check_quit_flag (void)
   int i, result = 0;
   const struct extension_language_defn *extlang;
 
+  if (quit_flag_cleanup)
+    return 0;
+
   ALL_ENABLED_EXTENSION_LANGUAGES (i, extlang)
     {
       if (extlang->ops->check_quit_flag != NULL)