[tip:perf/core] perf tools: Make perf_session__register_idle_thread drop the refcount

tip-bot for Masami Hiramatsu
2015-12-14T08:16:13Z

Commit-ID: 9d8b172f29ac0e5d1923d348e395e9643625ef7f
Gitweb: http://git.kernel.org/tip/9d8b172f29ac0e5d1923d348e395e9643625ef7f
Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
AuthorDate: Wed, 9 Dec 2015 11:11:23 +0900
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 10 Dec 2015 16:28:58 -0300

perf tools: Make perf_session__register_idle_thread drop the refcount

Note that since the thread was already inserted to the session
list, it will be released when the session is released.
Also, in perf_session__register_idle_thread() failure path,
the thread should be put before returning.

Refcnt debugger shows that the perf_session__register_idle_thread
gets the returned thread, but the caller (__cmd_top) does not
put the returned idle thread.

----
==== [0] ====
Unreclaimed thread@0x24e6240
Refcount +1 => 0 at
./perf(thread__new+0xe5) [0x4c8a75]
./perf(machine__findnew_thread+0x9a) [0x4bbdba]
./perf(perf_session__register_idle_thread+0x28) [0x4c63c8]
./perf(cmd_top+0xd7d) [0x43cf6d]
./perf() [0x47ba35]
./perf(main+0x617) [0x4225b7]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f06027c5af5]
./perf() [0x42272d]
Refcount +1 => 1 at
./perf(thread__get+0x2c) [0x4c8bcc]
./perf(machine__findnew_thread+0xee) [0x4bbe0e]
./perf(perf_session__register_idle_thread+0x28) [0x4c63c8]
./perf(cmd_top+0xd7d) [0x43cf6d]
./perf() [0x47ba35]
./perf(main+0x617) [0x4225b7]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f06027c5af5]
./perf() [0x42272d]
Refcount +1 => 2 at
./perf(thread__get+0x2c) [0x4c8bcc]
./perf(machine__findnew_thread+0x112) [0x4bbe32]
./perf(perf_session__register_idle_thread+0x28) [0x4c63c8]
./perf(cmd_top+0xd7d) [0x43cf6d]
./perf() [0x47ba35]
./perf(main+0x617) [0x4225b7]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f06027c5af5]
./perf() [0x42272d]
----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.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/20151209021122.10245.69707.stgit@localhost.localdomain
[ Drop the refcount in perf_session__register_idle_thread() ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-top.c | 2 +-
tools/perf/util/session.c | 11 +++++++----
tools/perf/util/session.h | 2 +-
3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 84fd636..785aa2d 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -964,7 +964,7 @@ static int __cmd_top(struct perf_top *top)
if (ret)
goto out_delete;

- if (perf_session__register_idle_thread(top->session) == NULL)
+ if (perf_session__register_idle_thread(top->session) < 0)
goto out_delete;

machine__synthesize_threads(&top->session->machines.host, &opts->target,
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index c35ffdd..9774686 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1311,17 +1311,20 @@ struct thread *perf_session__findnew(struct perf_session *session, pid_t pid)
return machine__findnew_thread(&session->machines.host, -1, pid);
}

-struct thread *perf_session__register_idle_thread(struct perf_session *session)
+int perf_session__register_idle_thread(struct perf_session *session)
{
struct thread *thread;
+ int err = 0;

thread = machine__findnew_thread(&session->machines.host, 0, 0);
if (thread == NULL || thread__set_comm(thread, "swapper", 0)) {
pr_err("problem inserting idle task.\n");
- thread = NULL;
+ err = -1;
}

- return thread;
+ /* machine__findnew_thread() got the thread, so put it */
+ thread__put(thread);
+ return err;
}

static void perf_session__warn_about_errors(const struct perf_session *session)
@@ -1676,7 +1679,7 @@ int perf_session__process_events(struct perf_session *session)
u64 size = perf_data_file__size(session->file);
int err;

- if (perf_session__register_idle_thread(session) == NULL)
+ if (perf_session__register_idle_thread(session) < 0)
return -ENOMEM;

if (!perf_data_file__is_pipe(session->file))
diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
index 3e900c0..5f792e3 100644
--- a/tools/perf/util/session.h
+++ b/tools/perf/util/session.h
@@ -89,7 +89,7 @@ struct machine *perf_session__findnew_machine(struct perf_session *session, pid_
}

struct thread *perf_session__findnew(struct perf_session *session, pid_t pid);
-struct thread *perf_session__register_idle_thread(struct perf_session *session);
+int perf_session__register_idle_thread(struct perf_session *session);

size_t perf_session__fprintf(struct perf_session *session, FILE *fp);