On Tue, 2011-07-12 at 12:27 +0300, Avi Kivity wrote: > On 07/12/2011 12:18 PM, Peter Zijlstra wrote: > > > > > > The guarantee is that the task was sleeping just before the function is > > > called. Of course it's woken up to run the function. > > > > > > The idea is that you run the function in a known safe point to avoid > > > extra synchronization. > > > > > > > I'd much rather we didn't wake the task and let it sleep, that's usually > > a very safe place for tasks to be. All you'd need is a guarantee it > > won't be woken up while you're doing your thing. > > But it means that 'current' is not set to the right value. If the > function depends on it, then it will misbehave. And in fact > preempt_notifier_register(), which is the function we want to call here, > does depend on current. > > Of course we need to find more users for this, but I have a feeling this > will be generally useful. The alternative is to keep adding bits to > thread_info::flags. Using TIF_bits sounds like a much better solution for this, wakeups are really rather expensive and its best to avoid extra if at all possible. -- 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
