internal error when setting watchpoints in programs with fork() on ppc

[Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>]

Hi,

testing upstream gdb, I'm facing this internal error when running gdb.threads/watchpoint-fork.exp testcase (from this non-upstreamed patch http://sourceware.org/ml/gdb-patches/2010-12/msg00043.html, found in gdb from Fedora and enterprise distros) on ppc64, more specifically in the `set follow-fork-mode child' part of the test:

../../gdb.git/gdb/frame.c:2375: internal-error: frame_cleanup_after_sniffer: Assertion `frame->prologue_cache == NULL' failed.

Actually, noticed that before this error, gdb fails to read r31 due to a wrong pid when issuing ptrace call on fetch_register() from ppc-linux-nat.c. This gdb-follow-child-stale-parent.patch from Jan Kratochvil (http://web.archiveorange.com/archive/v/iRKxrvg3CBOJl9wyV0pi, attached bellow) fixes this issue. Does this look ok for FSF gdb as well?

Thanks!
-- 
Edjunior

ps: since this is a patch made by Jan, I didn't add the changelog entry yet

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 7ec0788..d8f89f5 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -506,6 +506,9 @@ follow_fork (void)
 	  }
 	else
 	  {
+	    /* Possibly referenced PARENT is no longer valid.  */
+	    reinit_frame_cache ();
+
 	    /* This pending follow fork event is now handled, one way
 	       or another.  The previous selected thread may be gone
 	       from the lists by now, but if it is still around, need