linux-kernel - Re: Re: [PATCH tip/perf/core] perf probe: Load map before glob matching

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Message-ID: <555733D3.20805@hitachi.com>
Date:	Sat, 16 May 2015 21:10:59 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	Wang Nan <wangnan0@...wei.com>, a.p.zijlstra@...llo.nl,
	paulus@...ba.org, mingo@...hat.com, namhyung@...nel.org,
	lizefan@...wei.com, pi3orama@....com, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH tip/perf/core] perf probe: Load map before glob
 matching

On 2015/05/16 5:07, Arnaldo Carvalho de Melo wrote:
> Em Sat, May 16, 2015 at 12:15:45AM +0900, Masami Hiramatsu escreveu:
>> On 2015/05/15 21:14, Wang Nan wrote:
>>> Commit 4c859351226c920b227fec040a3b447f0d482af3 ("perf probe: Support
>>> glob wildcards for function name") introduces a problem:
>>>
>>>   # /root/perf probe kmem_cache_free
>>>  Failed to find symbol kmem_cache_free in kernel
>>>    Error: Failed to add events.
>>>
>>> The reason is the replacement of map__for_each_symbol_by_name() (by
>>> map__for_each_symbol()). Although their names are similay,
>>> map__for_each_symbol doesn't call map__load() and dso__sort_by_name()
>>> before searching. The missing of map__load() causes this problem
>>> because it search symbol before load dso map.
>>
>> Oops, yes. But I think we'd better fix map__for_each_symbol() to call
>> map__load() if the map is not loaded, doesn't it?
> 
> Well, that is something for a follow up patch, I'm applying his patch as
> it fixes a problem and is trivially correct.

OK, then I'm OK for this patch.

Thank you,

> 
> - Arnaldo
>  
>> Thank you,
>>
>>>
>>> This patch ensures map__load() is called before using
>>> map__for_each_symbol().
>>>
>>> After this patch:
>>>
>>>  # /root/perf probe kmem_cache_free
>>>   Added new event:
>>>     probe:kmem_cache_free (on kmem_cache_free%return)
>>>
>>> You can now use it in all perf tools, such as:
>>>
>>>         perf record -e probe:kmem_cache_free -aR sleep 1
>>>
>>> Signed-off-by: Wang Nan <wangnan0@...wei.com>
>>> ---
>>>  tools/perf/util/probe-event.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>>> index 2399dc4..1faa1e6 100644
>>> --- a/tools/perf/util/probe-event.c
>>> +++ b/tools/perf/util/probe-event.c
>>> @@ -2499,6 +2499,9 @@ static int find_probe_functions(struct map *map, char *name)
>>>  	struct symbol *sym;
>>>  	struct rb_node *tmp;
>>>  
>>> +	if (map__load(map, NULL) < 0)
>>> +		return 0;
>>> +
>>>  	map__for_each_symbol(map, sym, tmp) {
>>>  		if (strglobmatch(sym->name, name))
>>>  			found++;
>>>
>>
-- 
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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