Weaselweb reports on IRC:
2efb1f14f611f2ff8a380b703f3e8bcb8a95d1ad (Add GDB remote target description support for ARM4): starting with this commit the command "arm reg" stalls after printing "FIQ mode shadow registers". '(gdb) i r' still works as in "after output I get the gdb prompt again".
Please see if http://openocd.zylin.com/2278 helps.
The proposed change is confirmed to fix the issue.