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    Subject[patch 15/16] Tracepoints : documentation fix teardown
    Need a tracepoint_synchronize_unregister() before the end of exit() to make sure
    every probe callers have exited the non preemptible section and thus are not
    executing the probe code anymore.

    Impact: documentation update.

    Signed-off-by: Mathieu Desnoyers <>
    CC: Rusty Russell <>
    CC: "Frank Ch. Eigler" <>
    CC: Ingo Molnar <>
    CC: Lai Jiangshan <>
    CC: Peter Zijlstra <>
    CC: Steven Rostedt <>
    Documentation/tracepoints.txt | 10 ++++++----
    1 file changed, 6 insertions(+), 4 deletions(-)

    Index: linux-2.6-lttng/Documentation/tracepoints.txt
    --- linux-2.6-lttng.orig/Documentation/tracepoints.txt 2008-11-14 17:18:59.000000000 -0500
    +++ linux-2.6-lttng/Documentation/tracepoints.txt 2008-11-14 17:19:05.000000000 -0500
    @@ -70,10 +70,12 @@ Where :
    Connecting a function (probe) to a tracepoint is done by providing a probe
    (function to call) for the specific tracepoint through
    register_trace_subsys_eventname(). Removing a probe is done through
    -unregister_trace_subsys_eventname(); it will remove the probe sure there is no
    -caller left using the probe when it returns. Probe removal is preempt-safe
    -because preemption is disabled around the probe call. See the "Probe example"
    -section below for a sample probe module.
    +unregister_trace_subsys_eventname(); it will remove the probe.
    +marker_synchronize_unregister() must be called before the end of the module exit
    +function to make sure there is no caller left using the probe. This, and the
    +fact that preemption is disabled around the probe call, make sure that probe
    +removal and module unload are safe. See the "Probe example" section below for a
    +sample probe module.

    The tracepoint mechanism supports inserting multiple instances of the same
    tracepoint, but a single definition must be made of a given tracepoint name over
    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68

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