On Sat, Nov 22, 2014 at 09:04:48AM -0800, Shaohua Li wrote: ... > > + /* > > + * Theoretically, the following could test just ATOMIC; however, > > + * then we'd have to mask off DEAD separately as DEAD may be > > + * visible without ATOMIC if we race with percpu_ref_kill(). DEAD > > + * implies ATOMIC anyway. Test them together. > > + */ > > + if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC_DEAD)) > > return false; > > this sounds not the correct answer. the DEAD/ATOMIC bit can be set by > percpu_ref_kill() right after the check.
Yes, but that's why we're fetching @percpu_ptr with ACCESS_ONCE() before checking the flags. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
