Messages in this thread | | | Date | Mon, 24 Apr 2017 10:32:50 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86/refcount: Implement fast refcount_t handling |
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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.
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