Comment 7 for bug 620611

I've now completed an implementation of a GDB unwinder that supports backtracing out of the restart handler on the vector page. Patch is submitted upstream here:
http://sourceware.org/ml/gdb-patches/2011-02/msg00650.html

Note that this confirms kernel support for reading the vector page via ptrace is working fine now (tested with Linaro 2.6.37).

This fixes the following testsuite failures for me:
FAIL: gdb.server/ext-attach.exp: backtrace 2
FAIL: gdb.threads/attachstop-mt.exp: attach3 to stopped bt
FAIL: gdb.threads/attachstop-mt.exp: attach4, exit leaves process sleeping
FAIL: gdb.threads/attach-stopped.exp: threaded: attach2, exit leaves process sleeping
FAIL: gdb.threads/pthreads.exp: check backtrace from main thread
FAIL: gdb.threads/pthreads.exp: apply backtrace command to all three threads