linux-kernel - RE: [PATCH perf/core 14/22] perf: Fix dso__load

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Date:	Thu, 10 Dec 2015 08:52:46 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'Arnaldo Carvalho de Melo'" <acme@...nel.org>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Namhyung Kim" <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>
Subject: RE: [PATCH perf/core  14/22] perf: Fix dso__load_sym to put dso

From: Arnaldo Carvalho de Melo [mailto:acme@...nel.org]
>
>Em Wed, Dec 09, 2015 at 11:11:18AM +0900, Masami Hiramatsu escreveu:
>> +++ b/tools/perf/util/symbol-elf.c
>> @@ -1045,6 +1045,8 @@ int dso__load_sym(struct dso *dso, struct map *map,
>>  				/* kmaps already got it */
>>  				map__put(curr_map);
>>  				dsos__add(&map->groups->machine->dsos, curr_dso);
>> +				/* curr_map and machine->dsos already got it */
>> +				dso__put(curr_dso);
>>  				dso__set_loaded(curr_dso, map->type);
>>  			} else
>>  				curr_dso = curr_map->dso;
>
>Right, to make the code smaller, how about doing it this way, i.e. drop
>the reference once we have that curr_dso object with a ref held by
>curr_map, if curr_map doesn't get it, then we don't need and will drop
>it anyway:

But as above code, curr_dso is passed to dsos__add after curr_map is put.
Even if the curr_map is hold by kmaps, isn't the kmaps controlled by other pthreads?
If no, I'm OK if we move above dsos__add() before map__put() for safety, because
curr_dso is held by curr_map at that point.

Thank you,

>
>diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
>index 53f19968bfa2..84d787074152 100644
>--- a/tools/perf/util/symbol-elf.c
>+++ b/tools/perf/util/symbol-elf.c
>@@ -1026,8 +1026,8 @@ int dso__load_sym(struct dso *dso, struct map *map,
> 				curr_dso->long_name_len = dso->long_name_len;
> 				curr_map = map__new2(start, curr_dso,
> 						     map->type);
>+				dso__put(curr_dso);
> 				if (curr_map == NULL) {
>-					dso__put(curr_dso);
> 					goto out_elf_end;
> 				}
> 				if (adjust_kernel_syms) {
--
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