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SubjectRe: [PATCH 3/3] tracing/function-return-tracer: add the overrun field

* Steven Rostedt <rostedt@goodmis.org> wrote:

>
> On Tue, 18 Nov 2008, Ingo Molnar wrote:
> > > >
> > > > that reminds me: ti->ret_stack[] should be moved to task->ret_stack[].
> > > > That way we decouple its size from any kernel stack size limits.
> > > > (thread-info resides at one end of the kernel stack, on x86)
> > >
> > > Yeah, I recommended that to Frederic to save space. But that can be
> > > dangerous. Using task instead would be safer with the downside of
> > > making the task struct even bigger.
> >
> > We almost never put new stuff into thread_info - we have the
> > lockdep lock stack in the task structure too, for similar reasons.
>
> Yeah, it was just a recommendation, and perhaps not a good one ;-)
>
> Frederic, it is better if you move the array from the thread info to
> the task struct. It will take up more memory but it is a hell of a
> lot safer. The pro here definitely outways the con.

if the memory footprint starts mattering we could turn this into a
single pointer to an array - and add/remove these arrays (from all
tasks currently running) as the tracer is turned on/off.

Ingo


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