* Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > I will nevertheless suggest the following egregious hack to > get a consistent sample of one counter for some other CPU: > > a. Disable interrupts > b. Atomically exchange the bottom 32 bits of the > counter with the value zero. > c. Atomically exchange the top 32 bits of the counter > with the value zero. > d. Concatenate the values obtained in (b) and (c), which > is the snapshot value. Note, i have recently implemented full atomic64_t support on 32-bit x86, for the perfcounters code, based on the CMPXCHG8B instruction. Which, while not the lightest of instructions, is still much better than the sequence above. So i think a better approach would be to also add a dumb generic implementation for atomic64_t (using a global lock or so), and then generic code could just assume that atomic64_t always exists. It is far nicer - and faster as well - as the hack above, even on 32-bit x86. Ingo -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
