function-graph: allow unregistering twice
Impact: fix to permanent disabling of function graph tracer There should be nothing to prevent a tracer from unregistering a function graph callback more than once. This can simplify error paths. But currently, the counter does not account for mulitple unregistering of the function graph callback. If it happens, the function graph tracer will be permanently disabled. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -2719,6 +2719,9 @@ void unregister_ftrace_graph(void)
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{
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mutex_lock(&ftrace_lock);
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if (!unlikely(atomic_read(&ftrace_graph_active)))
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goto out;
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atomic_dec(&ftrace_graph_active);
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unregister_trace_sched_switch(ftrace_graph_probe_sched_switch);
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ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
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@ -2726,6 +2729,7 @@ void unregister_ftrace_graph(void)
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ftrace_shutdown(FTRACE_STOP_FUNC_RET);
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unregister_pm_notifier(&ftrace_suspend_notifier);
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out:
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mutex_unlock(&ftrace_lock);
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}
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