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SubjectRe: [PATCH 2/2] tracing/events/lockdep: move tracepoints within recursive protection

On Thu, 16 Apr 2009, Peter Zijlstra wrote:

> On Thu, 2009-04-16 at 12:15 -0400, Steven Rostedt wrote:
> > plain text document attachment
> > (0002-tracing-events-lockdep-move-tracepoints-within-recu.patch)
> > From: Steven Rostedt <srostedt@redhat.com>
> >
> > With the current location of the tracepoints in lockdep, the system
> > can hard lockup in minutes when the tracepoints are enabled.
> >
> > Moving the tracepoints outside inside the lockdep protection solves
> > the issue.
>
> NAK

Can we at least add this as a workaround. Basically, the lockdep
tracepoints are broken as is. I do not plan on changing the logic of the
events to prevent nesting. That's a feature I use. If we don't allow
nesting, we must drop events, which is bad.

The other answer is simply to remove the trace points in lockdep, until
they work again.

-- Steve


>
> the idea is to eventually move lockdep on top of the tracepoints. The
> tracer should grow to be more robust and handle recursion itself.
>
> Its likely a case of the tracer using a spinlock or mutex in the
> tracepoint code. When I did the tracepoints I converted one such to a
> raw_spinlock_t in the trace_print code.


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