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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>
This commit is contained in:
Steven Rostedt 2009-03-30 11:11:28 -04:00 committed by Ingo Molnar
parent 8b54e45b00
commit 2aad1b76e6
1 changed files with 4 additions and 0 deletions
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4
kernel/trace/ftrace.c
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@ -2719,6 +2719,9 @@ void unregister_ftrace_graph(void)
{
mutex_lock(&ftrace_lock);
if (!unlikely(atomic_read(&ftrace_graph_active)))
goto out;
atomic_dec(&ftrace_graph_active);
unregister_trace_sched_switch(ftrace_graph_probe_sched_switch);
ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
@ -2726,6 +2729,7 @@ void unregister_ftrace_graph(void)
ftrace_shutdown(FTRACE_STOP_FUNC_RET);
unregister_pm_notifier(&ftrace_suspend_notifier);
out:
mutex_unlock(&ftrace_lock);
}