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SubjectRe: [PATCH v3 2/3] soc: qcom: rpmh: Allow RPMH driver to be loaded as a module
On Wed, Apr 15, 2020 at 11:25 AM Matthias Kaehlcke <mka@chromium.org> wrote:
>
> Hi John,
>
> with commit efde2659b0fe ("drivers: qcom: rpmh-rsc: Use rcuidle
> tracepoints for rpmh") the rpmh-rsc driver fails to build as a
> module:
>
> drivers/soc/qcom/rpmh-rsc.c:281:3: error: implicit declaration of function 'trace_rpmh_send_msg_rcuidle' [-Werror,-Wimplicit-function-decr]
> trace_rpmh_send_msg_rcuidle(drv, tcs_id, j, msgid, cmd);
>
>
> The problem is that the _rcuidle() functions are not generated for modules:
>
> #ifndef MODULE
> #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \
> static inline void trace_##name##_rcuidle(proto) \
> { \
> if (static_key_false(&__tracepoint_##name.key)) \
> __DO_TRACE(&__tracepoint_##name, \
> TP_PROTO(data_proto), \
> TP_ARGS(data_args), \
> TP_CONDITION(cond), 1); \
> }
> #else
> #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
> #endif
>
> Not sure what the best solution would be in this case. Having the macro
> define a dummy function for modules would fix the build error, however it
> would be confusing that the event is traced when the driver is built-in,
> but not when it is built as a module.
>
> I imagine the goal behind making this driver a module is to have a single
> kernel image for multiple SoC platforms, without too much platform
> specific code in the kernel image itself.
>
> I guess the question is whether there any options for keeping the driver
> modular and having consistent tracing behavior, short of removing the
> tracepoint.

Yea. Stephen found that issue in -next last night once Bjorn added
the patches to his tree yesterday.

I've reached out to see if the restrictions on the trace_*_rcuidle
calls on modules is still necessary in this thread:
https://lore.kernel.org/lkml/CALAqxLV4rM74wuzuZ+BkUi+keccxkAxv30N4vrFO7CVQ5vnT1A@mail.gmail.com/

For now, I suggested Bjorn revert the patch in his tree, and I'll try
to figure out an alternative solution to the trace call.

thanks
-john

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