MUST-FIX: check the skbuff.c bit!
MUST-FIX: check the sched.c bit!

This doesn't look good. You declare it as a PER_CPU_LOCKED, but then
never use the extra lock to synchronize data.

Given that sock_proc_inuse_get() is a racy read anyway, the 'right' fix
would be to do something like:
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>