On 06/24/2013 11:36 PM, Tejun Heo wrote: > On Mon, Jun 24, 2013 at 10:55:35AM -0700, Tejun Heo wrote: >>> @@ -105,6 +106,7 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc) >>> ret += *pcount; >>> } >>> raw_spin_unlock(&fbc->lock); >>> + put_online_cpus_atomic(); >> >> I don't think this is necessary. CPU on/offlining is explicitly >> handled via the hotplug callback which synchronizes through fbc->lock. >> __percpu_counter_sum() racing with actual on/offlining doesn't affect >> correctness and adding superflous get_online_cpus_atomic() around it >> can be misleading. > > Ah, okay, so you added a debug feature which triggers warning if > online mask is accessed without synchronization. Exactly! > Yeah, that makes > sense and while the above is not strictly necessary, it probably is > better to just add it rather than suppressing the warning in a > different way. Yeah, I was beginning to scratch my head as to how to suppress the warning after I read your explanation as to why the calls to get/put_online_cpus_atomic() would be superfluous in this case... But as you said, simply invoking those functions is much simpler ;-) > Can you please at least add a comment explaining that? > Sure, will do. Thanks a lot Tejun! Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
