tracing_map_read_var_once 1982 kernel/trace/trace_events_hist.c 			var_val = tracing_map_read_var_once(var_elt, var_idx);
tracing_map_read_var_once  273 kernel/trace/tracing_map.h extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i);