Messages in this thread | | | Subject | Re: [PATCH] tracing/profile: Fix profile_disable vs module_unload | From | Peter Zijlstra <> | Date | Wed, 26 Aug 2009 09:26:28 +0200 |
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On Wed, 2009-08-26 at 15:10 +0800, Li Zefan wrote: > Peter Zijlstra wrote: > > On Wed, 2009-08-26 at 08:46 +0200, Peter Zijlstra wrote: > > > >> Aahh, I see the bug, its only ftrace that knows about the module, not > >> tracepoints themselves, _that_ needs fixing. > > > > You could possibly do something like: > > > > struct module *tp_mod = __module_address(&some_tp_symbol); > > struct module *cb_mod = __module_text_address(func); > > > > if (tp_mod && tp_mod != cb_mod) { > > ret = try_get_module(tp_mod); > > if (ret) > > goto fail; > > } > > > > in register_trace_##name() or thereabout. > > > > Actually I tried it, but it didn't work. As I said, You can't find > any tp symbol when registering tp callback. The same example again: > > In module bar, we have register_trace_foo() > In module foo, we have DEFINE_TRACE(foo) and trace_foo(). > > bar doesn't know any symbol of foo, so it can't bump foo's refcnt,
Well, clearly it knows about register_trace_foo() which itself knows at least one symbol that should be in module foo, right? How else could it register a callback in that module (if it were loaded)?
It appears to use some intermediate code, in which case the intermediate code knows about foo, which too solves our problem.
> *Note: you can load module bar without loading module foo*
In which case the tracepoint registration fails, right?
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