On Mon, 2018-09-24 at 11:01 -0700, Tejun Heo wrote: +AD4 Hello, Bart. +AD4 +AD4 On Fri, Sep 21, 2018 at 01:31:19PM -0700, Bart Van Assche wrote: +AD4 +AD4 +-void percpu+AF8-ref+AF8-resurrect(struct percpu+AF8-ref +ACo-ref) +AD4 +AD4 +-+AHs +AD4 +AD4 +- unsigned long +AF8AXw-percpu +ACo-percpu+AF8-count+ADs +AD4 +AD4 unsigned long flags+ADs +AD4 +AD4 +AD4 +AD4 spin+AF8-lock+AF8-irqsave(+ACY-percpu+AF8-ref+AF8-switch+AF8-lock, flags)+ADs +AD4 +AD4 +AD4 +AD4 - WARN+AF8-ON+AF8-ONCE(+ACE-percpu+AF8-ref+AF8-is+AF8-zero(ref))+ADs +AD4 +AD4 +- WARN+AF8-ON+AF8-ONCE(+ACE(ref-+AD4-percpu+AF8-count+AF8-ptr +ACY +AF8AXw-PERCPU+AF8-REF+AF8-DEAD))+ADs +AD4 +AD4 +- WARN+AF8-ON+AF8-ONCE(+AF8AXw-ref+AF8-is+AF8-percpu(ref, +ACY-percpu+AF8-count))+ADs +AD4 +AD4 So, this in itself is fine but I'm a bit worried that this might it +AD4 easier to abuse percpu+AF8-ref's dying mode. More specifically, it isn't +AD4 a good idea to depend on percpu+AF8-ref's implementation details from +AD4 outside - ie. the only guarantee there ever is that percpu+AF8-ref won't +AD4 give out new refs after -+AD4-percpu+AF8-ref is called - e.g. users can't +AD4 piggy back on implied rcu grace period. +AD4 +AD4 Can you please note that in the function comment? Provided that, +AD4 +AD4 Acked-by: Tejun Heo +ADw-tj+AEA-kernel.org+AD4 Hi Tejun, Thanks for the review. But could you please clarify what +ACI-after -+AD4-percpu+AF8-ref is called+ACI refers to? Thanks, Bart.
