Hi, I found strange behavior that if we set two or more probes on the same function, its callback called twice or more. Also, the stacktrace failed. And I found the root cause is here; On Wed, 8 Nov 2023 23:26:42 +0900 "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> wrote: > @@ -910,9 +917,10 @@ int register_ftrace_graph(struct fgraph_ops *gops) > */ > ftrace_graph_return = return_run; > ftrace_graph_entry = entry_run; > - > - ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET); > + command = FTRACE_START_FUNC_RET; > } > + > + ret = ftrace_startup(&gops->ops, command); So this patch registers ftrace_ops for each fgraph_ops to ftrace. This means that the ftrace_graph_func() will be called twice or more on the same function. Thus should I call ftrace_startup() once when the first fgraph_ops is registered? No, it's not enough. Actually each fgraph_ops can have different filters. We need to define a shared filter and combine new filters to one and use it. We also need to do it when a fgraph is unregistered. Is there any function which makes a new filter from two (or more) filters? Or, maybe we can make the common callback to find the previous ret entry on the ret_stack and reuse it. (In this case we don't need loop on each fgraph_array entry) Thank you, -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
