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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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