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

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Message-ID: <55560DA1.6090909@hitachi.com>
Date:	Sat, 16 May 2015 00:15:45 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Wang Nan <wangnan0@...wei.com>, a.p.zijlstra@...llo.nl,
	paulus@...ba.org, mingo@...hat.com, acme@...nel.org,
	namhyung@...nel.org
CC:	lizefan@...wei.com, pi3orama@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH tip/perf/core] perf probe: Load map before glob matching

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?

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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