RE: [PATCH perf/core 14/22] perf: Fix dso__load_sym to put dso

平松雅巳 / HIRAMATU，MASAMI
2015-12-10T08:52:52Z

From: Arnaldo Carvalho de Melo [mailto:acme@kernel.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) {