On Tue, Jul 21, 2009 at 10:24:08AM +0200, Jan Kiszka wrote: > Marcelo Tosatti wrote: > > Jan, > > > > This was suggested but we thought it might be safer to keep the > > get_cpu/put_cpu pair in case -rt kernels require it (which might be > > bullshit, but nobody verified). > > -rt stumbles over both patterns (that's why I stumbled over it in the > first place: get_cpu disables preemption, but spin_lock is a sleeping > lock under -rt) and actually requires requests_lock to become > raw_spinlock_t. Reordering get_cpu and spin_lock would be another > option, but not really a gain for both scenarios. I see. > So unless there is a way to make the whole critical section preemptible > (thus migration-agnostic), I think we can micro-optimize it like this. Can't you switch requests_lock to be raw_spinlock_t then? (or whatever is necessary to make it -rt compatible). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
