linux-kernel - Re: [RFC PATCH 1/3] perf probe: Init symbol as kprobe if any pev is kprobe

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Date:	Sat, 27 Jun 2015 17:30:58 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>, acme@...nel.org,
	ast@...mgrid.com, brendan.d.gregg@...il.com, daniel@...earbox.net,
	namhyung@...nel.org, paulus@...ba.org, a.p.zijlstra@...llo.nl,
	mingo@...hat.com, jolsa@...nel.org, dsahern@...il.com
CC:	linux-kernel@...r.kernel.org, lizefan@...wei.com,
	hekuang@...wei.com, xiakaixu@...wei.com, pi3orama@....com,
	cti.systems-productivity-manager.ts@...achi.com
Subject: Re: [RFC PATCH 1/3] perf probe: Init symbol as kprobe if any pev
 is kprobe

Hi Wang,

On 2015/06/27 16:34, Wangnan (F) wrote:
> 
> 
> On 2015/6/27 15:29, Masami Hiramatsu wrote:
>> On 2015/06/25 19:37, Wang Nan wrote:
>>> Before this patch, add_perf_probe_events() init symbol maps only for
>>> uprobe if the first pev passed to it is a uprobe event. However, with
>>> the incoming BPF uprobe support, now it will be possible to pass an
>>> array with combined kprobe and uprobe events to add_perf_probe_events().
>> This description is not correct. Actually, add_perf_probe_events already
>> supports mix of uprobes and kprobes. However, from the command line syntax
>> constrains the first elements of the probe_event arrays must be kprobes.
>> So, if the array starts with uprobes, no kprobes should be there.
>>
>>> This patch check all pevs instead of the first one, and init kernel
>>> symbol if any events is not uprobe.
>> Anyway, I prefer to call init_symbol_maps() with "false" :)
> 
> I also prefer "false", so I try to find whether all events are uprobe 
> instead
> of init_symbol_maps(true).
> 
> So for this patch only commit message needs to be corrected, the code is
> no problem, right?
> 

No, I meant you just need to change one line, as below.

-	ret = init_symbol_maps(pevs->uprobes);
+	ret = init_symbol_maps(false);

That's enough, I don't like to introduce a bool flag and loop.

Thanks,



> Thank you.
> 
>> Thank you,
>>
>>> Signed-off-by: Wang Nan <wangnan0@...wei.com>
>>> ---
>>>   tools/perf/util/probe-event.c | 15 ++++++++++++++-
>>>   1 file changed, 14 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>>> index b386d2f..a2b3026 100644
>>> --- a/tools/perf/util/probe-event.c
>>> +++ b/tools/perf/util/probe-event.c
>>> @@ -2802,8 +2802,21 @@ int cleanup_perf_probe_event(struct perf_probe_event *pev)
>>>   int add_perf_probe_events(struct perf_probe_event *pevs, int npevs, bool cleanup)
>>>   {
>>>   	int i, ret;
>>> +	bool user_only = true;
>>>   
>>> -	ret = init_symbol_maps(pevs->uprobes);
>>> +	/* If any pev is kprobe, init kernel symbols. */
>>> +	for (i = 0; i < npevs; i++) {
>>> +		if (!pevs[i].uprobes) {
>>> +			user_only = false;
>>> +			break;
>>> +		}
>>> +	}
>>> +
>>> +	/*
>>> +	 * Compiler can drop user_only:
>>> +	 *  ret = init_symbol_maps(i >= npevs);
>>> +	 */
>>> +	ret = init_symbol_maps(user_only);
>>>   	if (ret < 0)
>>>   		return ret;
>>>   
>>>
>>
> 
> 
> 


-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
--
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