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    Subject[Bugfix] unregister_trace_probe needs to be called under mutex
    Comment in unregister_trace_probe() says probe_lock will be held
    when it gets called. However there is a case where it might called
    without the probe_lock being held. Also since we are traversing the
    probe_list and deleting an element from the probe_list, probe_lock
    should be held.

    This was first pointed in uprobes traceevent review by Frederic
    Weisbecker here. (http://lkml.org/lkml/2010/5/12/106)

    This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip

    Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    ---

    diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
    index 4f11a56..67670cd 100644
    --- a/kernel/trace/trace_kprobe.c
    +++ b/kernel/trace/trace_kprobe.c
    @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
    pr_info("Delete command needs an event name.\n");
    return -EINVAL;
    }
    + mutex_lock(&probe_lock);
    tp = find_probe_event(event, group);
    if (!tp) {
    + mutex_unlock(&probe_lock);
    pr_info("Event %s/%s doesn't exist.\n", group, event);
    return -ENOENT;
    }
    /* delete an event */
    unregister_trace_probe(tp);
    free_trace_probe(tp);
    + mutex_unlock(&probe_lock);
    return 0;
    }


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