Re: [PATCH] arm64: perf: Simplify the ARMv8 PMUv3 event attributes

[Shaokun Zhang <zhangshaokun@hisilicon.com>]

Hi Will,

On 2019/11/1 0:08, Will Deacon wrote:
> On Wed, Oct 30, 2019 at 11:46:17AM +0800, Shaokun Zhang wrote:
>> For each PMU event, there is a ARMV8_EVENT_ATTR(xx, XX) and
>> &armv8_event_attr_xx.attr.attr. Let's redefine the ARMV8_EVENT_ATTR
>> to simplify the armv8_pmuv3_event_attrs.
>>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
>> ---
>>  arch/arm64/kernel/perf_event.c | 189 ++++++++++++++---------------------------
>>  1 file changed, 65 insertions(+), 124 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
>> index a0b4f1bca491..d0f084939bcf 100644
>> --- a/arch/arm64/kernel/perf_event.c
>> +++ b/arch/arm64/kernel/perf_event.c
>> @@ -159,132 +159,73 @@ armv8pmu_events_sysfs_show(struct device *dev,
>>  }
> 
> [...]
> 
>> +	(&((struct perf_pmu_events_attr[]) { \
>> +		{ .attr = __ATTR(name, 0444, armv8pmu_events_sysfs_show, NULL), \
>> +		  .id = config, } \
>> +	})[0].attr.attr)
> 
> I don't get the need for the array here. Why can't you do:
> 
> 	(&((struct perf_pmu_events_attr) {
> 		.attr = ...,
> 		.id = ...,
> 	}).attr.attr)
> 
> ?

I try it and there is a compiler error:

zhangshaokun@ubuntu:~/linux$ make Image -j64
  CALL    scripts/atomic/check-atomics.sh
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  CC      arch/arm64/kernel/perf_event.o
arch/arm64/kernel/perf_event.c:162:13: error: unknown field ‘attr’ specified in initializer
  (&((struct perf_pmu_events_attr) { \
             ^
arch/arm64/kernel/perf_event.c:168:2: note: in expansion of macro ‘ARMV8_EVENT_ATTR’
  ARMV8_EVENT_ATTR(sw_incr, ARMV8_PMUV3_PERFCTR_SW_INCR),
  ^
arch/arm64/kernel/perf_event.c:162:13: warning: braces around scalar initializer
  (&((struct perf_pmu_events_attr) { \
             ^
arch/arm64/kernel/perf_event.c:168:2: note: in expansion of macro ‘ARMV8_EVENT_ATTR’
  ARMV8_EVENT_ATTR(sw_incr, ARMV8_PMUV3_PERFCTR_SW_INCR),

It seems that it became completely anonymous and the compiler can't find its member.

Thanks,
Shaokun

> 
> Will
> 
> .
> 


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