Re: [PATCH 0/2] ftrace: updates to tip
From: Ingo Molnar
Date: Fri Jan 16 2009 - 11:02:31 EST
* Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> On Fri, 16 Jan 2009, Ingo Molnar wrote:
> > >
> > > But I do notice that not all functions produce a valid stack trace.
> > > Maybe it would be better to add that api :-?
> >
> > yes - i think that API would be more intuitive, and that way people could
> > mix more interesting functions (with stack traces) with less important
> > functions (no stack traces).
>
> Ah, that's the point. We can't mix and match on these. Either all
> functions that are traced do the stack trace, or none do. This is where
> the new api may be confusing. [...]
that would be confusing indeed.
> [...] We can register a function to be traced via the function pointer,
> and we can pick which functions to trace, but we can not separate out
> different functions for different traces.
Why not? We could have a hash of all traced functions with metadata
attached. Since patching functions in/out would be a relatively rare
operation, this would be a highly efficient read-mostly hash.
Ingo
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