On Wednesday 22 July 2015 10:14 AM, Daniel Axtens wrote:
> On Thu, 2015-07-16 at 16:43 +0530, Madhavan Srinivasan wrote:
>> Add code to create event/format attributes and attribute groups for
>> each nest pmu.
>>
>> Cc: Michael Ellerman <m...@ellerman.id.au>
>> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
>> Cc: Paul Mackerras <pau...@samba.org>
>> Cc: Anton Blanchard <an...@samba.org>
>> Cc: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
>> Cc: Anshuman Khandual <khand...@linux.vnet.ibm.com>
>> Cc: Stephane Eranian <eran...@google.com>
>> Signed-off-by: Madhavan Srinivasan <ma...@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/perf/nest-pmu.c | 65
>> ++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 65 insertions(+)
>>
>> diff --git a/arch/powerpc/perf/nest-pmu.c b/arch/powerpc/perf/nest-pmu.c
>> index c4c08e4dee55..f3418bdec1cd 100644
>> --- a/arch/powerpc/perf/nest-pmu.c
>> +++ b/arch/powerpc/perf/nest-pmu.c
>> @@ -13,6 +13,17 @@
>> static struct perchip_nest_info p8_nest_perchip_info[P8_NEST_MAX_CHIPS];
>> static struct nest_pmu *per_nest_pmu_arr[P8_NEST_MAX_PMUS];
>>
>> +PMU_FORMAT_ATTR(event, "config:0-20");
>> +static struct attribute *p8_nest_format_attrs[] = {
>> + &format_attr_event.attr,
>> + NULL,
>> +};
>> +
>> +static struct attribute_group p8_nest_format_group = {
>> + .name = "format",
>> + .attrs = p8_nest_format_attrs,
>> +};
>> +
>> static int nest_event_info(struct property *pp, char *name,
>> struct nest_ima_events *p8_events, int string, u32 val)
>> {
>> @@ -46,6 +57,56 @@ static int nest_event_info(struct property *pp, char
>> *name,
>> return 0;
>> }
>>
>> +/*
>> + * Populate event name and string in attribute
>> + */
>> +static struct attribute *dev_str_attr(const char *name, const char *str)
>> +{
>> + struct perf_pmu_events_attr *attr;
>> +
>> + attr = kzalloc(sizeof(*attr), GFP_KERNEL);
>> +
>> + sysfs_attr_init(&attr->attr.attr);
>> +
>> + attr->event_str = str;
>> + attr->attr.attr.name = name;
>> + attr->attr.attr.mode = 0444;
>> + attr->attr.show = perf_event_sysfs_show;
>> +
>> + return &attr->attr.attr;
> So I asked you about this before, and you pointed me to
> perf_event_sysfs_show. Looking at that in kernel/events/core.c, it looks
> like that uses container_of to pull out the perf_pmu_events_attr. So I
> guess that is at least mostly correct.
>
> I'm hoping something else uses container_of to pull out attr->attr, so
> that they can actually grab the attr->attr.show function pointer, so
> that perf_event_sysfs_show actually gets called. Where would that be?
OK, what we return is the device attribute struct which also have sysfs_ops.
So ->show and ->store are those entries in the strucutre and here we only
populate show ops using perf_event_sysfs_show. Now at the time of
pmu registering, we end up calling device_add->device_create_file->
sysfs_create_file which will end up adding a sysfs device file linked to
this
->show ops.
>> +}
>> +
>> +static int update_events_in_group(
>> + struct nest_ima_events *p8_events, int idx, struct nest_pmu *pmu)
>> +{
>> + struct attribute_group *attr_group;
>> + struct attribute **attrs;
>> + int i;
>> +
>> + /*
>> + * Allocate memory for both event attribute group and for
>> + * event attributes array.
>> + */
>> + attr_group = kzalloc(((sizeof(struct attribute *) * (idx + 1)) +
>> + sizeof(*attr_group)), GFP_KERNEL);
>> + if (!attr_group)
>> + return -ENOMEM;
>> +
>> + /*
>> + * Assign memory for event attribute array
>> + */
>> + attrs = (struct attribute **)(attr_group + 1);
>> + attr_group->name = "events";
>> + attr_group->attrs = attrs;
> I am super uncomfortable with this block, especially the assignment to
> attrs. I *think* you're trying to allocate an attribute group and a set
> of attributes, but you've combined the allocation into one big
> contiguous chunk, and then you're trying to tease them apart. Is that
> necessary? Could it be two allocs, one for the attribute_group and one
> for the attribute?
I wanted to avoid two function calls here, but this is not a hot path
This happens at the pmu init time (booting), so I guess we can have
two allocs here.
>
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