Re: Review of LKST probe points

[William Cohen <wcohen at redhat dot com>]

Frank Ch. Eigler wrote:

Hi,

> > > [...]
> > > Can you outline what these are for?
> >
> > Some of the LKST_ operations are for management of LKST. There events 
> > are listed in lkst-events-2.1.pdf. [...]
> > [...]
>
>
> I guess I don't understand what "management of LKST" means.

House keeping things for LKST, not actual probe things. For exampl end 
of the buffer and initialization of lkst are not interesting for data 
analysis.

> > [...]  It would be nice if the probe could be [placed] inside the
> > spinlock region of the instrumented code. This would ensure that
> > data is gathered and minimize perturbations by attempting to get the
> > lock twice.
>
>
> That's true.  In case it's not clear though, sometimes we may have to
> traverse a lock-protected data structure from a routine that is not
> involved directly with it, like a timer interrupt.  It is possible not
> lock these data structures from within a probe that's traversing them,
> but that of course risks reading junk data on SMP.

Yes, grabbing a another lock at that time would be troublesome.

-Will