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Bug 1330127

Summary: SIGSEGV if GLib MainLoop is run from thread to e.g. capture DBus signals
Product: Red Hat Enterprise Linux 7 Reporter: Jaroslav Škarvada <jskarvad>
Component: dbusAssignee: David King <dking>
Status: CLOSED NOTABUG QA Contact: Desktop QE <desktop-qa-list>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.2CC: vbenes
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-04-26 16:14:04 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
Reproducer none

Description Jaroslav Škarvada 2016-04-25 12:38:10 UTC 
Created attachment 1150443 [details]
Reproducer

Description of problem:
It seems the code lacks locking somewhere. I am currently not sure whether it is DBus or GLib issue, but as it is hanging in the libdbus I am filling the bug against DBus.

Version-Release number of selected component (if applicable):
dbus-libs-1.6.12-13.el7.x86_64

How reproducible:
Always

Steps to Reproduce:
1. for (( i=1; i < 1000; i++ )); do ./test.py; done

Actual results:
Often SIGSEGVs

Expected results:
No SIGSEGVs

Additional info:
It works OK on fedora (e.g. dbus-libs-1.10.8-1.fc23.x86_64).
Comment 1 Jaroslav Škarvada 2016-04-25 12:39:55 UTC 
Backtrace:

#0  link_before (link=link@entry=0x1efa9b8, before_this_link=0x7f590000, list=list@entry=0x1f7b020) at dbus-list.c:120
#1  _dbus_list_prepend_link (list=list@entry=0x1f7b020, link=link@entry=0x1efa9b8) at dbus-list.c:325
#2  0x00007f5954b26fe9 in _dbus_list_append_link (list=list@entry=0x1f7b020, link=link@entry=0x1efa9b8) at dbus-list.c:307
#3  0x00007f5954b1748f in _dbus_message_add_counter_link (message=message@entry=0x1f7afb0, link=link@entry=0x1efa9b8) at dbus-message.c:304
#4  0x00007f5954b1750f in _dbus_message_add_counter (message=0x1f7afb0, counter=0x20736b0) at dbus-message.c:338
#5  0x00007f5954b23849 in _dbus_transport_queue_messages (transport=transport@entry=0x206a3c0) at dbus-transport.c:1140
#6  0x00007f5954b241e6 in do_reading (transport=0x206a3c0) at dbus-transport-socket.c:851
#7  0x00007f5954b248f6 in socket_do_iteration (transport=0x206a3c0, flags=6, timeout_milliseconds=<optimized out>) at dbus-transport-socket.c:1162
#8  0x00007f5954b235ff in _dbus_transport_do_iteration (transport=0x206a3c0, flags=32483768, flags@entry=6, timeout_milliseconds=360, timeout_milliseconds@entry=25000)
    at dbus-transport.c:976
#9  0x00007f5954b0cd7c in _dbus_connection_do_iteration_unlocked (connection=connection@entry=0x1f6bd50, pending=pending@entry=0x1efaa40, flags=flags@entry=6, 
    timeout_milliseconds=timeout_milliseconds@entry=25000) at dbus-connection.c:1234
#10 0x00007f5954b0d75d in _dbus_connection_block_pending_call (pending=0x1efaa40) at dbus-connection.c:2415
#11 0x00007f5954b1d5fa in dbus_pending_call_block (pending=<optimized out>) at dbus-pending-call.c:748
#12 0x00007f5954b0dd3a in dbus_connection_send_with_reply_and_block (connection=0x1f6bd50, message=message@entry=0x2054940, timeout_milliseconds=timeout_milliseconds@entry=-1, 
    error=error@entry=0x7ffc0559f5f0) at dbus-connection.c:3530
#13 0x00007f5954d510df in Connection_send_message_with_reply_and_block (self=0x2033cb0, args=<optimized out>) at ../../_dbus_bindings/conn-methods.c:498
#14 0x00007f595cc89bd4 in call_function (oparg=<optimized out>, pp_stack=0x7ffc0559f760) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4098
#15 PyEval_EvalFrameEx (
    f=f@entry=Frame 0x213ad40, for file /usr/lib64/python2.7/site-packages/dbus/connection.py, line 651, in call_blocking (self=<unknown at remote 0x2033cb0>, bus_name='org.freedesktop.DBus', object_path='/org/freedesktop/DBus', dbus_interface='org.freedesktop.DBus', method='GetNameOwner', signature='s', args=('com.redhat.tuned',), timeout=<float at remote 0x1e3bee8>, byte_arrays=False, kwargs={'utf8_strings': True}, get_args_opts={'byte_arrays': False, 'utf8_strings': True}, message=<dbus.lowlevel.MethodCallMessage at remote 0x7f595d1005a0>), 
    throwflag=throwflag@entry=0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:2740
#16 0x00007f595cc8b1ed in PyEval_EvalCodeEx (co=<optimized out>, globals=<optimized out>, locals=locals@entry=0x0, args=args@entry=0x2035378, argcount=7, kws=kws@entry=0x1fb0650, 
    kwcount=kwcount@entry=1, defs=defs@entry=0x7f595d05fe78, defcount=defcount@entry=2, closure=0x0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:3330
#17 0x00007f595cc181bd in function_call (func=<function at remote 0x7f595cfef7d0>, arg=<unknown at remote 0x2035360>, kw=<unknown at remote 0x1f7b640>)
    at /usr/src/debug/Python-2.7.5/Objects/funcobject.c:526
#18 0x00007f595cbf30c3 in PyObject_Call (func=func@entry=<function at remote 0x7f595cfef7d0>, arg=arg@entry=<unknown at remote 0x2035360>, kw=kw@entry=<unknown at remote 0x1f7b640>)
    at /usr/src/debug/Python-2.7.5/Objects/abstract.c:2529
#19 0x00007f595cc86427 in ext_do_call (nk=<optimized out>, na=<optimized out>, flags=<optimized out>, pp_stack=0x7ffc0559fa20, func=<function at remote 0x7f595cfef7d0>)
    at /usr/src/debug/Python-2.7.5/Python/ceval.c:4411
#20 PyEval_EvalFrameEx (
    f=f@entry=Frame 0x213aa20, for file /usr/lib64/python2.7/site-packages/dbus/bus.py, line 361, in get_name_owner (self=<unknown at remote 0x2033cb0>, bus_name='com.redhat.tuned', keywords=<unknown at remote 0x1f7b640>), throwflag=throwflag@entry=0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:2779
#21 0x00007f595cc89990 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7ffc0559fb80, func=<function at remote 0x7f595cfefed8>) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4184
#22 call_function (oparg=<optimized out>, pp_stack=0x7ffc0559fb80) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4119
#23 PyEval_EvalFrameEx (
    f=f@entry=Frame 0x213a820, for file /usr/lib64/python2.7/site-packages/dbus/bus.py, line 175, in activate_name_owner (self=<unknown at remote 0x2033cb0>, bus_name='com.redhat.tuned'), 
    throwflag=throwflag@entry=0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:2740
#24 0x00007f595cc89990 in fast_function (nk=<optimized out>, na=2, n=2, pp_stack=0x7ffc0559fce0, func=<function at remote 0x7f595cfefb18>) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4184
#25 call_function (oparg=<optimized out>, pp_stack=0x7ffc0559fce0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4119
#26 PyEval_EvalFrameEx (
    f=f@entry=Frame 0x1f29730, for file /usr/lib64/python2.7/site-packages/dbus/proxies.py, line 248, in __init__ (self=<unknown at remote 0x20f7310>, conn=<unknown at remote 0x2033cb0>, bus_name='com.redhat.tuned', object_path='/Tuned', introspect='com.redhat.tuned.control', follow_name_owner_changes=False, kwargs={}, bus=None, named_service=None), 
    throwflag=throwflag@entry=0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:2740
#27 0x00007f595cc8b1ed in PyEval_EvalCodeEx (co=<optimized out>, globals=<optimized out>, locals=locals@entry=0x0, args=args@entry=0x7f595d0ae958, argcount=4, kws=kws@entry=0x203aa08, 
    kwcount=kwcount@entry=2, defs=defs@entry=0x7f595cfe52a8, defcount=defcount@entry=5, closure=0x0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:3330
#28 0x00007f595cc181bd in function_call (func=<function at remote 0x7f595cfee230>, arg=(<unknown at remote 0x20f7310>, <unknown at remote 0x2033cb0>, 'com.redhat.tuned', '/Tuned'), 
    kw={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False}) at /usr/src/debug/Python-2.7.5/Objects/funcobject.c:526
#29 0x00007f595cbf30c3 in PyObject_Call (func=func@entry=<function at remote 0x7f595cfee230>, 
    arg=arg@entry=(<unknown at remote 0x20f7310>, <unknown at remote 0x2033cb0>, 'com.redhat.tuned', '/Tuned'), 
    kw=kw@entry={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False}) at /usr/src/debug/Python-2.7.5/Objects/abstract.c:2529
#30 0x00007f595cc020b5 in instancemethod_call (func=<function at remote 0x7f595cfee230>, arg=(<unknown at remote 0x20f7310>, <unknown at remote 0x2033cb0>, 'com.redhat.tuned', '/Tuned'), 
    kw={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False}) at /usr/src/debug/Python-2.7.5/Objects/classobject.c:2602
#31 0x00007f595cbf30c3 in PyObject_Call (func=func@entry=<instancemethod at remote 0x7f595d122b40>, arg=arg@entry=<unknown at remote 0x20178c0>, 
    kw=kw@entry={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False}) at /usr/src/debug/Python-2.7.5/Objects/abstract.c:2529
#32 0x00007f595cc4a187 in slot_tp_init (self=<optimized out>, args=<unknown at remote 0x20178c0>, kwds={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False})
    at /usr/src/debug/Python-2.7.5/Objects/typeobject.c:5692
#33 0x00007f595cc48e9f in type_call (type=<optimized out>, args=<unknown at remote 0x20178c0>, kwds={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False})
    at /usr/src/debug/Python-2.7.5/Objects/typeobject.c:745
#34 0x00007f595cbf30c3 in PyObject_Call (func=func@entry=<type at remote 0x1f6c980>, arg=arg@entry=<unknown at remote 0x20178c0>, 
    kw=kw@entry={'introspect': 'com.redhat.tuned.control', 'follow_name_owner_changes': False}) at /usr/src/debug/Python-2.7.5/Objects/abstract.c:2529
#35 0x00007f595cc8738c in do_call (nk=<optimized out>, na=3, pp_stack=0x7ffc055a02c0, func=<type at remote 0x1f6c980>) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4316
#36 call_function (oparg=<optimized out>, pp_stack=0x7ffc055a02c0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4121
#37 PyEval_EvalFrameEx (
    f=f@entry=Frame 0x1f293e0, for file /usr/lib64/python2.7/site-packages/dbus/bus.py, line 241, in get_object (self=<unknown at remote 0x2033cb0>, bus_name='com.redhat.tuned', object_path='/Tuned', introspect='com.redhat.tuned.control', follow_name_owner_changes=False, kwargs={}, named_service=None), throwflag=throwflag@entry=0)
    at /usr/src/debug/Python-2.7.5/Python/ceval.c:2740
#38 0x00007f595cc8b1ed in PyEval_EvalCodeEx (co=<optimized out>, globals=<optimized out>, locals=locals@entry=0x0, args=<optimized out>, argcount=argcount@entry=4, kws=0x1ee2d78, 
    kwcount=0, defs=0x7f595d05ff08, defcount=2, closure=closure@entry=0x0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:3330
#39 0x00007f595cc8989f in fast_function (nk=<optimized out>, na=4, n=4, pp_stack=0x7ffc055a04c0, func=<function at remote 0x7f595cfefb90>) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4194
#40 call_function (oparg=<optimized out>, pp_stack=0x7ffc055a04c0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:4119
#41 PyEval_EvalFrameEx (f=f@entry=Frame 0x1ee2be0, for file ./test.py, line 17, in <module> (), throwflag=throwflag@entry=0) at /usr/src/debug/Python-2.7.5/Python/ceval.c:2740
#42 0x00007f595cc8b1ed in PyEval_EvalCodeEx (co=co@entry=0x7f595d0c39b0, 
    globals=globals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    locals=locals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    args=args@entry=0x0, argcount=argcount@entry=0, kws=kws@entry=0x0, kwcount=kwcount@entry=0, defs=defs@entry=0x0, defcount=defcount@entry=0, closure=closure@entry=0x0)
    at /usr/src/debug/Python-2.7.5/Python/ceval.c:3330
#43 0x00007f595cc8b2f2 in PyEval_EvalCode (co=co@entry=0x7f595d0c39b0, 
    globals=globals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    locals=locals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>})
    at /usr/src/debug/Python-2.7.5/Python/ceval.c:689
#44 0x00007f595cca472f in run_mod (mod=<optimized out>, filename=filename@entry=0x7ffc055a13ec "./test.py", 
    globals=globals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    locals=locals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    flags=flags@entry=0x7ffc055a0720, arena=arena@entry=0x1e5ef30) at /usr/src/debug/Python-2.7.5/Python/pythonrun.c:1374
#45 0x00007f595cca58ee in PyRun_FileExFlags (fp=fp@entry=0x1ee7240, filename=filename@entry=0x7ffc055a13ec "./test.py", start=start@entry=257, 
    globals=globals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, 'threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    locals=locals@entry={'GLib': <unknown at remote 0x2031610>, 'DBusGMainLoop': <built-in function DBusGMainLoop>, 'dbus': <module at remote 0x7f595d079bb0>, 'thread': <unknown at remote 0x2031d90>, '__builtins__': <module at remote 0x7f595d140b08>, 'bus': <unknown at remote 0x2033cb0>, '__file__': './test.py', 'main_loop': <unknown at remote 0x207fe88>, '__package__': None, '
threading': <module at remote 0x7f595d0837f8>, 'time': <module at remote 0x7f595d079328>, '__name__': '__main__', '__doc__': None, 'thread_code': <unknown at remote 0x20f8410>}, 
    closeit=closeit@entry=1, flags=flags@entry=0x7ffc055a0720) at /usr/src/debug/Python-2.7.5/Python/pythonrun.c:1360
#46 0x00007f595cca6b79 in PyRun_SimpleFileExFlags (fp=fp@entry=0x1ee7240, filename=filename@entry=0x7ffc055a13ec "./test.py", closeit=closeit@entry=1, flags=flags@entry=0x7ffc055a0720)
    at /usr/src/debug/Python-2.7.5/Python/pythonrun.c:952
#47 0x00007f595cca7093 in PyRun_AnyFileExFlags (fp=fp@entry=0x1ee7240, filename=filename@entry=0x7ffc055a13ec "./test.py", closeit=closeit@entry=1, flags=flags@entry=0x7ffc055a0720)
    at /usr/src/debug/Python-2.7.5/Python/pythonrun.c:756
#48 0x00007f595ccb7caf in Py_Main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/Python-2.7.5/Modules/main.c:640
#49 0x00007f595bee4b15 in __libc_start_main (main=0x4006f0 <main>, argc=2, ubp_av=0x7ffc055a08e8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, 
    stack_end=0x7ffc055a08d8) at libc-start.c:274
#50 0x0000000000400721 in _start ()
Comment 2 David King 2016-04-26 16:14:04 UTC 
This does not seem like a dbus bug, but something in your code that you need to fix, or possibly something in the dbus Python bindings or maybe even dbus-glib. You can ask on the upstream mailing list for support, if you need assistance developing thread-safe code which uses dbus:

https://lists.freedesktop.org/mailman/listinfo/dbus

You should note the documentation for dbus-glib threading support:

https://dbus.freedesktop.org/doc/dbus-glib/dbus-glib-DBusGConnection.html#dbus-g-thread-init

Specifically, the part that reads "Note that dbus-glib's GObject mapping is explicitly *not* thread-safe." and "dbus-glib is never thread-safe". You should additionally note the dbus-python documentation:

https://pypi.python.org/pypi/dbus-python

Specifically, the part that states "[dbus-python] uses libdbus (which has known problems with multi-threaded use)"