Messages in this thread | | | Subject | Re: [PATCH] tracing/profile: Fix profile_disable vs module_unload | From | Peter Zijlstra <> | Date | Wed, 26 Aug 2009 09:39:45 +0200 |
| |
On Wed, 2009-08-26 at 15:31 +0800, Li Zefan wrote: > 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.
*blink*
so we'll succeed in registering a tracepoint we know isn't there?
| |