On Fri, 27 Jan 2012 00:31:13 +0400 Glauber Costa [off-list ref] wrote:

On the specifics of this bug, I verified this config compiles okay in 
your tree + my patches at the day I last sent them. I also verified it 
breaks on the tree today.

The reason seems to be that some other patch tweaked with the header 
files in an unrelated patch, and the static_branch definition that was 
getting to us in sock.h, is no longer getting there.

Including it explicitly fixes it here. I will again pass through a 
battery of randconfigs on my own, and send you a fix.

Which is one of the reasons we have Rule 1 in Documentation/SubmitChecklist:

1: If you use a facility then #include the file that defines/declares
   that facility.  Don't depend on other header files pulling in ones
   that you use.

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au