linux-kernel - [PATCH 21/37] perf machine: Fix machine__findnew_module

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Date:	Thu, 19 Nov 2015 14:53:07 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 21/37] perf machine: Fix machine__findnew_module_map to put registered map

From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Fix machine object to drop the reference to the map object after it
inserted it into machine->kmaps.

refcnt debugger shows what happened:
  ----
  ==== [2] ====
  Unreclaimed map: 0x346f750
  Refcount +1 => 1 at
    ./perf(map__new2+0xb5) [0x4bdea5]
    ./perf() [0x4b8aaf]
    ./perf(modules__parse+0xfc) [0x4a9cbc]
    ./perf() [0x4b83c0]
    ./perf(machine__create_kernel_maps+0x148) [0x4bb208]
    ./perf(machine__new_host+0xfa) [0x4bb3fa]
    ./perf(init_probe_symbol_maps+0x93) [0x5062b3]
    ./perf() [0x455ffa]
    ./perf(cmd_probe+0x6c) [0x4566bc]
    ./perf() [0x47abc5]
    ./perf(main+0x610) [0x421f90]
    /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f5373899af5]
    ./perf() [0x4220a9]
  Refcount +1 => 2 at
    ./perf(maps__insert+0x9a) [0x4bfd4a]
    ./perf() [0x4b8acb]
    ./perf(modules__parse+0xfc) [0x4a9cbc]
    ./perf() [0x4b83c0]
    ./perf(machine__create_kernel_maps+0x148) [0x4bb208]
    ./perf(machine__new_host+0xfa) [0x4bb3fa]
    ./perf(init_probe_symbol_maps+0x93) [0x5062b3]
    ./perf() [0x455ffa]
    ./perf(cmd_probe+0x6c) [0x4566bc]
    ./perf() [0x47abc5]
    ./perf(main+0x610) [0x421f90]
    /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f5373899af5]
    ./perf() [0x4220a9]
  Refcount -1 => 1 at
    ./perf(map_groups__exit+0x94) [0x4bea54]
    ./perf(machine__delete+0x3d) [0x4b91ed]
    ./perf(exit_probe_symbol_maps+0x28) [0x506358]
    ./perf() [0x45628a]
    ./perf(cmd_probe+0x6c) [0x4566bc]
    ./perf() [0x47abc5]
    ./perf(main+0x610) [0x421f90]
    /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f5373899af5]
    ./perf() [0x4220a9]
  ----

This pattern clearly shows that the refcnt of the map is acquired twice
by map__new2 and maps__insert but released onlu once at
map_groups__exit, when we purge its maps rbtree.

Since maps__insert already reference counted the map, we have to drop
the constructor (map__new2) reference count right after inserting it.

These happened in machine__findnew_module_map, as below.

  ----
  # eu-addr2line -e ./perf -f 0x4b8aaf
  machine__findnew_module_map inlined at util/machine.c:1046
  in machine__create_module
  util/machine.c:582
  # eu-addr2line -e ./perf -f 0x4b8acb
  map_groups__insert inlined at util/machine.c:585
  in machine__create_module
  util/map.h:208
  ----

(note that both are at util/machine.c:58X which is
 machine__findnew_module_map)

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/20151118064020.30709.40499.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/machine.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 8b303ff20289..0487d7795f13 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -585,6 +585,8 @@ struct map *machine__findnew_module_map(struct machine *machine, u64 start,
 
 	map_groups__insert(&machine->kmaps, map);
 
+	/* Put the map here because map_groups__insert alread got it */
+	map__put(map);
 out:
 	free(m.name);
 	return map;
-- 
2.1.0

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