>>>>> "MD" == Matthias Drochner <drochner@zelux6.zel.kfa-juelich.de> writes:

MD> When committing the KGDB changes 2 days ago
MD> I missed that the current NetBSD gdb can't issue
MD> line breaks on serial connections.
MD> To get it working now, you should use a plain
MD> GNU gdb-4.16 (and type "set remotebreak 1").
MD> Sorry for the confution.

Or, if you don't care about other remote debugging stuff working right,
you can apply this crock patch:

Index: remote.c
===================================================================
RCS file: /u3/cvsroot/src/gnu/usr.bin/gdb/gdb/remote.c,v
retrieving revision 1.1.1.1
diff -c -r1.1.1.1 remote.c
*** remote.c	1996/03/29 02:20:17	1.1.1.1
--- remote.c	1997/08/15 02:06:50
***************
*** 421,427 ****
    if (remote_debug)
      printf ("remote_interrupt called\n");
  
!   SERIAL_WRITE (remote_desc, "\003", 1); /* Send a ^C */
  }
  
  static void (*ofunc)();
--- 421,428 ----
    if (remote_debug)
      printf ("remote_interrupt called\n");
  
! /*  SERIAL_WRITE (remote_desc, "\003", 1); /* Send a ^C */
!   SERIAL_SEND_BREAK(remote_desc);
  }
  
  static void (*ofunc)();