djprobes status

[Ingo Molnar]

On Fri, 2006-09-15 at 09:49 -0400, Satoshi Oshima wrote:
> The problems currently we are trying to solve is...
> 
> (1)finding the safe place to put probes
> (2)unregistration of the buffer that is used as out of line execution
>    under kernel level preemption(CONFIG_PREEMPT=y)
> 
> We have some idea to solve problem (1), and we are working on it.
> 
> Currently (2) is very difficult to solve. This problem is equivalent
> to the problem of finding RCU quiescent state without rcu_read_lock()/
> rcu_read_unlock(). We need to add a couple of primitives to find such
> state. But it is not easy. We may be going to push djprobe without 
> kernel level preemption support like current kprobe-booster.
> 

could you tell me a bit more about how you have tried to solve (2) and
why it didnt work? I cannot see any fundamental difficulty in (2), in
fact i find problem (1) much, much scarier! :-) (please also outline the
basic problem to me, maybe i'm not seeing the difficulties out of
ignorance.)

	Ingo