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@xxxxxxxxxxx>
> >
> > 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
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html