* Ingo Molnar ([email protected]) wrote:
> > > static int x;
> > >
> > > void func(int a)
> > > {
> > > ...
> > > MARK(event, a);
> > > ...
> > > }
> > >
> > > if a dynamic tracer installs a probe into that MARK() spot, it will have
> > > access to 'a', but it can also have access to 'x'. While a static
> > > in-source markup for _static tracers_, if it also wanted to have the 'x'
> > > information, would also have to add 'x' as a parameter:
> > >
> > > MARK(event, a, x);
> > >
> >
> > Hi,
> >
> > If I may, if nothing marks the interest of the tracer in the "x"
> > variable, what happens when a kernel guru changes it for y (because it
> > looks a lot better). The code will not compile anymore when the markup
> > marks the interest for x, when your "dynamic tracer" markup will
> > simply fail to find the information. My point is that the markup of
> > the interesting variables should follow code changes, otherwise it
> > will have to be constantly updated elsewhere (hmm ? Documentation/
> > someone ?)
>
> yeah - but it shows (as you have now recognized it too) that even static
> markup for dynamic tracers _can_ be fundamentally different, just
> because dynamic tracers have access to information that static tracers
> dont.
>
> (Karim still disputes it, and he is still wrong.)
The following example voids your example : there are ways to implement static
markers that *could* have access to those variables. (implementation detail)
int x = 5;
#define MARK(a) printk(a, x)
voi func(int a)
{
...
MARK(a);
...
}
Mathieu
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