[tip:perf/core] perf symbols: Fix dso__load_sym to put dso

tip-bot for Masami Hiramatsu
2015-12-14T08:16:35Z

Commit-ID: e7a7865cc0da306542db0b9205cb0a467f59e33d
Gitweb: http://git.kernel.org/tip/e7a7865cc0da306542db0b9205cb0a467f59e33d
Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
AuthorDate: Wed, 9 Dec 2015 11:11:18 +0900
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 10 Dec 2015 16:29:32 -0300

perf symbols: Fix dso__load_sym to put dso

Fix dso__load_sym to put dso because dsos__add already got it.

Refcnt debugger explain the problem:
----
==== [0] ====
Unreclaimed dso: 0x19dd200
Refcount +1 => 1 at
./perf(dso__new+0x1ff) [0x4a62df]
./perf(dso__load_sym+0xe89) [0x503509]
./perf(dso__load_vmlinux+0xbf) [0x4aa77f]
./perf(dso__load_vmlinux_path+0x8c) [0x4aa8dc]
./perf() [0x50539a]
./perf(convert_perf_probe_events+0xd79) [0x50ad39]
./perf() [0x45600f]
./perf(cmd_probe+0x6c) [0x4566bc]
./perf() [0x47abc5]
./perf(main+0x610) [0x421f90]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f74dd0efaf5]
./perf() [0x4220a9]
Refcount +1 => 2 at
./perf(dso__get+0x34) [0x4a65f4]
./perf(map__new2+0x76) [0x4be216]
./perf(dso__load_sym+0xee1) [0x503561]
./perf(dso__load_vmlinux+0xbf) [0x4aa77f]
./perf(dso__load_vmlinux_path+0x8c) [0x4aa8dc]
./perf() [0x50539a]
./perf(convert_perf_probe_events+0xd79) [0x50ad39]
./perf() [0x45600f]
./perf(cmd_probe+0x6c) [0x4566bc]
./perf() [0x47abc5]
./perf(main+0x610) [0x421f90]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f74dd0efaf5]
./perf() [0x4220a9]
Refcount +1 => 3 at
./perf(dsos__add+0xf3) [0x4a6bc3]
./perf(dso__load_sym+0xfc1) [0x503641]
./perf(dso__load_vmlinux+0xbf) [0x4aa77f]
./perf(dso__load_vmlinux_path+0x8c) [0x4aa8dc]
./perf() [0x50539a]
./perf(convert_perf_probe_events+0xd79) [0x50ad39]
./perf() [0x45600f]
./perf(cmd_probe+0x6c) [0x4566bc]
./perf() [0x47abc5]
./perf(main+0x610) [0x421f90]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f74dd0efaf5]
./perf() [0x4220a9]
Refcount -1 => 2 at
./perf(dso__put+0x2f) [0x4a664f]
./perf(map_groups__exit+0xb9) [0x4bee29]
./perf(machine__delete+0xb0) [0x4b93d0]
./perf(exit_probe_symbol_maps+0x28) [0x506718]
./perf() [0x45628a]
./perf(cmd_probe+0x6c) [0x4566bc]
./perf() [0x47abc5]
./perf(main+0x610) [0x421f90]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f74dd0efaf5]
./perf() [0x4220a9]
Refcount -1 => 1 at
./perf(dso__put+0x2f) [0x4a664f]
./perf(machine__delete+0xfe) [0x4b941e]
./perf(exit_probe_symbol_maps+0x28) [0x506718]
./perf() [0x45628a]
./perf(cmd_probe+0x6c) [0x4566bc]
./perf() [0x47abc5]
./perf(main+0x610) [0x421f90]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f74dd0efaf5]
./perf() [0x4220a9]
----
So, in the dso__load_sym, dso is gotten 3 times, by dso__new,
map__new2, and dsos__add. The last 2 is actually released by
map_groups and machine__delete correspondingly. However, the
first reference by dso__new, is never released.

Committer note:

Changed the place where the reference count is dropped to:

Fix it by dropping it right after creating curr_map, since we know that
either that operation failed and we need to drop the dso refcount or
that it succeed and we have it referenced via curr_map->dso.

Then only drop the curr_map refcount after we call dsos__add() to make
sure we hold a reference to it via curr_map->dso.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20151209021118.10245.49869.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/symbol-elf.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 53f1996..562b8eb 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) {
@@ -1042,9 +1042,14 @@ int dso__load_sym(struct dso *dso, struct map *map,
}
curr_dso->symtab_type = dso->symtab_type;
map_groups__insert(kmaps, curr_map);
+ /*
+ * Add it before we drop the referece to curr_map,
+ * i.e. while we still are sure to have a reference
+ * to this DSO via curr_map->dso.
+ */
+ dsos__add(&map->groups->machine->dsos, curr_dso);
/* kmaps already got it */
map__put(curr_map);
- dsos__add(&map->groups->machine->dsos, curr_dso);
dso__set_loaded(curr_dso, map->type);
} else
curr_dso = curr_map->dso;