On 12/07/2012 11:46 PM, Tejun Heo wrote: > Hello, again. > > On Fri, Dec 07, 2012 at 09:57:24AM -0800, Tejun Heo wrote: >> possible. Also, I think the right approach would be auditing each >> get_online_cpus_atomic() callsites and figure out proper locking order >> rather than implementing a construct this unusual especially as >> hunting down the incorrect cases shouldn't be difficult given proper >> lockdep annotation. > > On the second look, it looks like you're implementing proper > percpu_rwlock semantics
Ah, nice! I didn't realize that I was actually doing what I intended to avoid! ;-) Looking at the implementation of lglocks, and going by Oleg's earlier comment that we just need to replace spinlock_t with rwlock_t in them to get percpu_rwlocks, I was horrified at the kinds of circular locking dependencies that they would be prone to, unless used carefully. So I devised this scheme to be safe, while still having relaxed rules. But if *this* is what percpu_rwlocks should ideally look like, then great! :-) > as readers aren't supposed to induce circular > dependency directly. Yep, in this scheme, nobody will end up in circular dependency. > Can you please work with Oleg to implement > proper percpu-rwlock and use that for CPU hotplug rather than > implementing it inside CPU hotplug? > Sure, I'd be more than happy to! Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
