On Mon, Jun 03, 2013 at 04:02:29PM -0700, Kent Overstreet wrote: > The cmpxcgh() was just to ensure the debug check didn't race, which was > a bit excessive. The caller is supposed to do the appropriate > synchronization, which means percpu_ref_kill() can just do a simple > store. > > Signed-off-by: Kent Overstreet <koverstr...@google.com>
Applied to percpu/for-3.11. The only concern I have left now is that we now have bitwise-and and test instead of just test in the hot path (get/put) to test whether the percpu part is alive. As x86 has single and-and-test instruction which doesn't require an output register, this only adds a single instruction but this may lead to more overhead on other architectures. The and-and-test was added because RCU free needs to have access to the percpu pointer after the pointer is killed and can be removed by adding another field to struct percpu_ref which remembers the pointer separately from the original percpu pointer, which I think is a better trade-off given that it makes the hot path lighter and adding another pointer field to struct percpu_ref isn't really gonna affect anything. Plus, it'd also make the code simpler. Anyways, it's not a big concern at this point and we can address it later. Thanks a lot, everyone! -- 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/
