perf buildid-list: Fix segfault when show DSOs with hits

commit: f3b623b8490a ("perf tools: Reference count struct thread")
appends every thread->node to dead_threads in machine__remove_thread()
and list_del_init() this node in thread__put().

perf_event__exit_del_thread() releases thread wihout using
machine__remove_thread(), and causes a NULL pointer crash when
list_del_init(&thread->node) is called. Fix this by using
machine_remove_thread() instead of using thread__put() directly.

This problem can be reproduced as following:

  $ perf record ls
  $ perf buildid-list --with-hits
  [ 3874.195070] perf[1018]: segfault at 0 ip 00000000004b0b15 sp
  00007ffc35b44780 error 6 in perf[400000+166000]
  Segmentation fault

After this patch:
  $ perf record ls
  $ perf buildid-list --with-hits
  bc23e7c3281e542650ba4324421d6acf78f4c23e /proc/kcore
  643324cb0e969f30c56d660f167f84a150845511 [vdso]
  0000000000000000000000000000000000000000 /bin/busybox
  ...

Signed-off-by: He Kuang <hekuang@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1428658500-6483-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/build-id.c

@@ -59,12 +59,8 @@ static int perf_event__exit_del_thread(struct perf_tool *tool __maybe_unused,
 	dump_printf("(%d:%d):(%d:%d)\n", event->fork.pid, event->fork.tid,
 		    event->fork.ppid, event->fork.ptid);
 
-	if (thread) {
-		rb_erase(&thread->rb_node, &machine->threads);
-		if (machine->last_match == thread)
-			thread__zput(machine->last_match);
-		thread__put(thread);
-	}
+	if (thread)
+		machine__remove_thread(machine, thread);
 
 	return 0;
 }

tools/perf/util/machine.c

@@ -14,8 +14,6 @@
 #include "unwind.h"
 #include "linux/hash.h"
 
-static void machine__remove_thread(struct machine *machine, struct thread *th);
-
 static void dsos__init(struct dsos *dsos)
 {
 	INIT_LIST_HEAD(&dsos->head);
@@ -1256,7 +1254,7 @@ out_problem:
 	return 0;
 }
 
-static void machine__remove_thread(struct machine *machine, struct thread *th)
+void machine__remove_thread(struct machine *machine, struct thread *th)
 {
 	if (machine->last_match == th)
 		thread__zput(machine->last_match);

tools/perf/util/machine.h

@@ -120,6 +120,7 @@ int machine__init(struct machine *machine, const char *root_dir, pid_t pid);
 void machine__exit(struct machine *machine);
 void machine__delete_threads(struct machine *machine);
 void machine__delete(struct machine *machine);
+void machine__remove_thread(struct machine *machine, struct thread *th);
 
 struct branch_info *sample__resolve_bstack(struct perf_sample *sample,
 					   struct addr_location *al);