* exceptions.cc (signal_exit): Reset all mutos owned by the main thread.

* fhandler.h: Define *_output_mutex macros for serializing tty output.
(fhandler_termios): Remove restart_output_event.  Define dummy output mutex
methods.
(fhandler_pty_master): Remove unneeded fixup_after_fork method.
* fhandler_termios.cc (fhandler_termios::line_edit): Acquire output_mutex when
CTRL-S is hit.  Release it on CTRL-Q.
* fhandler_tty.cc (fhandler_pty_master::process_slave_output): Remove
inappropriate OutputStopped test here.  Just use the output mutex.
(fhandler_pty_master::fhandler_pty_master): Remove obsolete reference to
restart_output_event.
(fhandler_tty_common::close): Ditto.
(fhandler_pty_master::set_close_on_exec): Ditto.
(fhandler_pty_master::fixup_after_fork): Delete.
* tty.cc (tty::common_init): Ditto.
* sync.cc (muto::reset): New method.
* sync.h: Declare above method.

winsup/cygwin/exceptions.cc

@@ -1007,6 +1007,12 @@ signal_exit (int rc)
   /* If the exception handler gets a trap, we could recurse awhile.
      If this is non-zero, skip the cleaning up and exit NOW.  */
 
+  muto *m;
+  /* FIXME: Make multi-thread aware */
+  for (m = muto_start.next;  m != NULL; m = m->next)
+    if (m->unstable () || m->owner () == mainthread.id)
+      m->reset ();
+
   rc = EXIT_SIGNAL | (rc << 8);
   if (exit_already++)
     {