Put placeholders in PF_flag so we can see how holey it is.
Suggested-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/YxctoffFFPXONESt@hirez.programming.kicks-ass.net