On Thu, Nov 29, 2012 at 10:45:04AM -0800, Andi Kleen wrote: > Kent Overstreet <koverstreet@xxxxxxxxxx> writes: > > > This implements a refcount with similar semantics to > > atomic_get()/atomic_dec_and_test(), that starts out as just an atomic_t > > but dynamically switches to per cpu refcounting when the rate of > > gets/puts becomes too high. > > This will only work if you put on the same CPU as you get, right? Nope, no such restriction. > In this case I would rather use RCU. It's clearly unusable for anything > blocking (or not get_cpu) Normally RCU already handles the "ref count for short non > blocking case" The kioctx refcount isn't held for short nonblocking duration, io_getevents() holds it and may block for arbitrarily long. Maybe SRCU could be made to work for it (I havent' really looked at the RCU variants) but it doesn't seem like a good idea. This thing really is just a refcount, the percpu part isn't exposed to the user at all. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
