On Fri, Apr 21, 2017 at 03:09:39PM -0700, Kees Cook wrote: > This patch ports the x86-specific atomic overflow handling from PaX's > PAX_REFCOUNT to the upstream refcount_t API. This is an updated version > from PaX that eliminates the saturation race condition by resetting the > atomic counter back to the INT_MAX saturation value on both overflow and > underflow. To win a race, a system would have to have INT_MAX threads > simultaneously overflow before the saturation handler runs. And is this impossible? Highly unlikely I'll grant you, but absolutely impossible? Also, you forgot nr_cpus in your bound. Afaict the worst case here is O(nr_tasks + 3*nr_cpus). Because PaX does it, is not a correctness argument. And this really wants one.
