Messages in this thread | | | Date | Wed, 26 Aug 2009 15:31:06 +0800 | From | Li Zefan <> | Subject | Re: [PATCH] tracing/profile: Fix profile_disable vs module_unload |
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15:26, Peter Zijlstra wrote: > 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? >
No, it won't fail. ;)
Instead, when foo is loaded, tracepoint_update_probe_range() will be called, and the probe registered in bar will be added to the tracepoint.
Maybe we can do something in tracepoint_update_probe_range(). I'll try.
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