Messages in this thread | | | Date | Tue, 21 Apr 2015 07:19:30 -0500 | From | Ron Rechenmacher <> | Subject | Re: [PATCH] tracing: Export key trace event symbols |
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I see in the reference I mentioned below (https://patches.linaro.org/28821/), and in the current mm source, that some tracepoint symbols are already EXPORTed, but not _GPL. I do not know the fine points between "GPL-ed" and "non-GPL-ed" symbol exporting. Would it make a difference if my patch proposed non-GPL exporting?
Ron Rechenmacher wrote on 04/21/15 07:04: > > > Christoph Hellwig wrote on 04/21/15 01:10: >> >> Which (in-tree) module fails with this? I don't think anyone should >> actually register a symbol. >> > > I see you (Christoph Hellwig) have asked this question in a similar context > (see https://patches.linaro.org/28821/). > This question does not seem to make sense because: > 1) the external module is not registering a _symbol_ but more > precisely a tracepoint _function_ as the whole tracepoint system allows for > _multiple_ functions to be called for each tracepoint declared in the kernel. > 2) It's not the point that an in-tree module would fail. Again, the tracepoint > system allows for _multiple_functions_ to be defined/registered for each tracepoint > and _in_the_earlier_kernels_(i.e. 3.10.x and many others),_external_modules_could_ > _register_ one or more _additional_functions_ to be called. > > IF you're specifically saying that external modules should not register additional > tracepoint functions, my question would simply be: why do you think this? > > To give you an example of the usefulness of continuing to allow this (continuation > from earlier kernels): the kernel scheduling has a tracepoint defined; of course a > critical operation for any kernel. I use to be able to insert a module which would > collect my own statistics on when and what switching was going on on what CPU cores. > I can think of many other potential reasons that this would be useful for external > modules. To think that tracepoints would only be useful for in-tree development is, > perhaps, (not meaning to offend) short sighted. >
-- Ron Rechenmacher Engineer Fermi National Accelerator Laboratory Batavia, IL 60510
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