Re: [PATCH 1/2] drivers/nvdimm: Fix build failure when CONFIG_PERF_EVENTS is not set

[Dan Williams <dan.j.williams@intel.com>]

On Fri, Mar 18, 2022 at 4:42 AM Kajol Jain <kjain@linux.ibm.com> wrote:
>
> The following build failure occures when CONFIG_PERF_EVENTS is not set
> as generic pmu functions are not visible in that scenario.
>
> |-- s390-randconfig-r044-20220313
> |   |-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_migrate_context
> |   |-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_register
> |   `-- nd_perf.c:(.text):undefined-reference-to-perf_pmu_unregister
>
> Similar build failure in nds32 architecture:
> nd_perf.c:(.text+0x21e): undefined reference to `perf_pmu_migrate_context'
> nd_perf.c:(.text+0x434): undefined reference to `perf_pmu_register'
> nd_perf.c:(.text+0x57c): undefined reference to `perf_pmu_unregister'
>
> Fix this issue by adding check for CONFIG_PERF_EVENTS config option
> and disabling the nvdimm perf interface incase this config is not set.
>
> Also removed function declaration of perf_pmu_migrate_context,
> perf_pmu_register, perf_pmu_unregister functions from nd.h as these are
> common pmu functions which are part of perf_event.h and since we
> are disabling nvdimm perf interface incase CONFIG_PERF_EVENTS option
> is not set, we not need to declare them in nd.h
>
> Fixes: 0fab1ba6ad6b ("drivers/nvdimm: Add perf interface to expose
> nvdimm performance stats") (Commit id based on linux-next tree)
> Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
> Link: https://lore.kernel.org/all/62317124.YBQFU33+s%2FwdvWGj%25lkp@intel.com/
> Reported-by: kernel test robot <lkp@intel.com>
> ---
>  drivers/nvdimm/Makefile | 2 +-
>  include/linux/nd.h      | 7 ++++---
>  2 files changed, 5 insertions(+), 4 deletions(-)
>
> ---
> - This fix patch changes are added and tested on top of linux-next tree
>   on the 'next-20220315' branch.
> ---
> diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
> index 3fb806748716..ba0296dca9db 100644
> --- a/drivers/nvdimm/Makefile
> +++ b/drivers/nvdimm/Makefile
> @@ -15,7 +15,7 @@ nd_e820-y := e820.o
>  libnvdimm-y := core.o
>  libnvdimm-y += bus.o
>  libnvdimm-y += dimm_devs.o
> -libnvdimm-y += nd_perf.o
> +libnvdimm-$(CONFIG_PERF_EVENTS) += nd_perf.o
>  libnvdimm-y += dimm.o
>  libnvdimm-y += region_devs.o
>  libnvdimm-y += region.o
> diff --git a/include/linux/nd.h b/include/linux/nd.h
> index 7b2ccbdc1cbc..a4265eaf5ae8 100644
> --- a/include/linux/nd.h
> +++ b/include/linux/nd.h
> @@ -8,8 +8,10 @@
>  #include <linux/ndctl.h>
>  #include <linux/device.h>
>  #include <linux/badblocks.h>
> +#ifdef CONFIG_PERF_EVENTS
>  #include <linux/perf_event.h>

Why must this not be included? Doesn't it already handle the
CONFIG_PERF_EVENTS=n case internally?

>  #include <linux/platform_device.h>

I notice now that this platform-device header should have never been
added in the first place, just forward declare:

struct platform_device;

> +#endif
>
>  enum nvdimm_event {
>         NVDIMM_REVALIDATE_POISON,
> @@ -25,6 +27,7 @@ enum nvdimm_claim_class {
>         NVDIMM_CCLASS_UNKNOWN,
>  };
>
> +#ifdef CONFIG_PERF_EVENTS
>  #define NVDIMM_EVENT_VAR(_id)  event_attr_##_id
>  #define NVDIMM_EVENT_PTR(_id)  (&event_attr_##_id.attr.attr)

Why must these be inside the ifdef guard?

>
> @@ -63,9 +66,7 @@ extern ssize_t nvdimm_events_sysfs_show(struct device *dev,
>
>  int register_nvdimm_pmu(struct nvdimm_pmu *nvdimm, struct platform_device *pdev);
>  void unregister_nvdimm_pmu(struct nvdimm_pmu *nd_pmu);

Shouldn't there also be stub functions in the CONFIG_PERF_EVENTS=n case?

static inline int register_nvdimm_pmu(struct nvdimm_pmu *nvdimm,
struct platform_device *pdev)
{
    return -ENXIO;
}

static inline void unregister_nvdimm_pmu(struct nvdimm_pmu *nd_pmu)
{
}

> -void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu);
> -int perf_pmu_register(struct pmu *pmu, const char *name, int type);
> -void perf_pmu_unregister(struct pmu *pmu);

Yeah, I should have caught these earlier.

> +#endif
>
>  struct nd_device_driver {
>         struct device_driver drv;
> --
> 2.31.1
>