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

[kajoljain <kjain@linux.ibm.com>]

On 3/22/22 07:40, Dan Williams wrote:
> 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;

Hi Dan,
    Sure I will do the required changes.

Thanks,
Kajol Jain
> 
>> +#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
>>