From: Steven Rostedt 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 --- kernel/trace/ftrace.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 1752a63..f1ed080 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -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); } -- 1.6.2.1 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/