linux-kernel - Re: [PATCH v3 2/3] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter

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Date:	Mon, 3 Aug 2015 18:32:45 +0800
From:	xiakaixu <xiakaixu@...wei.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	<ast@...mgrid.com>, <davem@...emloft.net>, <acme@...nel.org>,
	<mingo@...hat.com>, <masami.hiramatsu.pt@...achi.com>,
	<jolsa@...nel.org>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>,
	<hekuang@...wei.com>
Subject: Re: [PATCH v3 2/3] bpf: Implement function bpf_perf_event_read()
 that get the selected hardware PMU conuter

于 2015/8/3 17:34, Peter Zijlstra 写道:
> On Thu, Jul 23, 2015 at 09:42:41AM +0000, Kaixu Xia wrote:
>> +static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5)
>> +{
>> +	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
>> +	struct bpf_array *array = container_of(map, struct bpf_array, map);
>> +	struct perf_event *event;
>> +
>> +	if (index >= array->map.max_entries)
>> +		return -E2BIG;
>> +
>> +	event = array->events[index];
>> +	if (!event)
>> +		return -EBADF;
>> +
>> +	if (event->state != PERF_EVENT_STATE_ACTIVE)
>> +		return -ENOENT;
>> +
>> +	if (event->oncpu != raw_smp_processor_id() &&
>> +	    event->ctx->task != current)
>> +		return -EINVAL;
>> +
>> +	if (event->attr.inherit)
>> +		return -EINVAL;
>> +
>> +	__perf_event_read(event);
>> +
>> +	return perf_event_count(event);
>> +}
> 
> Please no poking of event internal state outside of perf code.

Thanks for your review. I will move it to kernel/events/core.c.
> 
> .
> 


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