Messages in this thread | | | Subject | Re: [PATCH 3/3] ftrace: Do not call stub functions in control loop | From | Steven Rostedt <> | Date | Mon, 08 Apr 2013 22:16:45 -0400 |
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On Tue, 2013-04-09 at 10:08 +0800, zhangwei(Jovi) wrote: > On 2013/4/9 4:49, Steven Rostedt wrote: > > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> > > > > The function tracing control loop used by perf spits out a warning > > if the called function is not a control function. This is because > > the control function references a per cpu allocated data structure > > on struct ftrace_ops that is not allocated for other types of > > functions. > > > > commit 0a016409e42 "ftrace: Optimize the function tracer list loop" > > > > Had an optimization done to all function tracing loops to optimize > > for a single registered ops. Unfortunately, this allows for a slight > > race when tracing starts or ends, where the stub function might be > > called after the current registered ops is removed. In this case we > > get the following dump: > >
> Involve stable? 3.8 kernel user would need this fix.
Why? commit 0a016409e42 "ftrace: Optimize the function tracer list loop" was added for 3.9. 3.8 has:
op = rcu_dereference_raw(ftrace_control_list); while (op != &ftrace_list_end) { if (!ftrace_function_local_disabled(op) && ftrace_ops_test(op, ip)) op->func(ip, parent_ip, op, regs);
op = rcu_dereference_raw(op->next); };
The stub function will never get called.
-- Steve
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