Re: [patch] kprobes for 2.5.73 with single-stepping out-of-line

["Vamsi Krishna S ." <vamsi@in.ibm.com>]

On Wed, Jun 25, 2003 at 01:52:02PM +0200, Andi Kleen wrote:
> On Wed, Jun 25, 2003 at 04:11:13PM +0530, Vamsi Krishna S . wrote:
> > On Tue, Jun 24, 2003 at 06:01:09PM +0200, Andi Kleen wrote:
> > > "Vamsi Krishna S ." <vamsi@in.ibm.com> writes:
> > > 
> > > 
> > > > +static struct kprobe *current_kprobe;
> > > 
> > > This global variable is quite unclean. It looks like it is for passing
> > > function arguments around. Why is it needed? 
> > > 
> > This is used for keeping track of the probe that is currently being
> > handled. This information is needed to be kept across a 
> > trap 3 - singlestep - trap 1. So, we set store the current probe in
> > this variable while handling trap 3, for use while handling the
> > subsequent trap 1.
> 
> But how can this be SMP safe? Do you hold a lock during all this?
> 
Yes.. in the interests of keeping the locking to a minimum, only one
probe can be handled at a time, even on SMP.

> -Andi
Thanks,
Vamsi.
-- 
Vamsi Krishna S.
IBM Software Lab, Bangalore.
Ph: +91 80 5044959
Internet: vamsi@in.ibm.com