From: "Anil" <anil.s.keshavamurthy@intel.com>

In flush_workqueue() for a single_threaded_worqueue case the code flushes the
same cpu_workqueue_struct for each online_cpu.

Change things so that we only perform the flush once in this case.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>