[Thread]: Fix crash in ThreadStackManager during system shutdown

[yufengwangca]

Problem

Observe the system crash in ThreadStackManager during system shutdown.

From the backtrace, it seems the last reference on a connection was dropped without closing the connection.

(gdb) bt
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1 0x00007ffff7531859 in __GI_abort () at abort.c:79
#2 0x00007ffff7c56ed2 in () at /lib/x86_64-linux-gnu/libdbus-1.so.3
#3 0x00007ffff7c79570 in _dbus_strdup () at /lib/x86_64-linux-gnu/libdbus-1.so.3
#4 0x000055555558c1ec in chip::DeviceLayer::ThreadStackManagerImpl::DBusConnectionDeleter::operator()(DBusConnection*) (this=0x5555555fae88 chip::DeviceLayer::ThreadStackManagerImpl::sInstance+8, aConnection=0x555555639860)
at ../../src/platform/Linux/ThreadStackManagerImpl.h:102
#5 0x000055555558ccd6 in std::unique_ptr<DBusConnection, chip::DeviceLayer::ThreadStackManagerImpl::DBusConnectionDeleter>::~unique_ptr()
(this=0x5555555fae88 chip::DeviceLayer::ThreadStackManagerImpl::sInstance+8, __in_chrg=) at /usr/include/c++/9/bits/unique_ptr.h:292
#6 0x000055555558e212 in chip::DeviceLayer::ThreadStackManagerImpl::~ThreadStackManagerImpl() (this=0x5555555fae80 chip::DeviceLayer::ThreadStackManagerImpl::sInstance, __in_chrg=)
at ../../src/platform/Linux/ThreadStackManagerImpl.h:95
#7 0x00007ffff7555a27 in __run_exit_handlers (status=0, listp=0x7ffff76f7718 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at exit.c:108
#8 0x00007ffff7555be0 in __GI_exit (status=) at exit.c:139
#9 0x000055555556d6f2 in chip::Shell::cmd_exit(int, char**) (argc=0, argv=0x7fffffffdd18) at ../../src/lib/shell/commands.cpp:41
#10 0x000055555556ce75 in chip::Shell::Shell::ExecCommand(int, char**)Python Exception <class 'RecursionError'> maximum recursion depth exceeded while getting the str of an object:
(this=0x5555555f8140 chip::Shell::Shell::theShellRoot, argc=1, argv=0x7fffffffdd10) at ../../src/lib/shell/shell.cpp:141
#11 0x000055555556d1ab in chip::Shell::Shell::TaskLoop(void*) (arg=0x0) at ../../src/lib/shell/shell.cpp:223
#12 0x000055555556ca71 in chip::Shell::shell_task(void*) (arg=0x0) at ../../src/lib/shell/shell.h:187
#13 0x000055555556cae3 in main() () at ../../examples/shell/standalone/main.cpp:50

Summary of Changes

Close the dbus connection before freeing the dbus connection.