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#182 ✓resolved
Vinay Sajip

Using with gevent causes segfault

Reported by Vinay Sajip | October 2nd, 2013 @ 03:41 PM

I have an application using gevent 0.13.8 + psycopg2 2.5.1 which segfaults when an attempt is made to 'green' psycopg using a slight variant of Daniele Varrazzo's code provided by Denis Bilenko here.

A snippet from my code:

    if __name__ == '__main__':
        from gevent import monkey
        from gevent.pywsgi import WSGIServer
        from psycopg_green import make_psycopg_green
        monkey.patch_all()
        #make_psycopg_green() # uncommenting this line -> segfault
        ...
        app = WebApp(get_session_factory())
        WSGIServer(('', 8000), app, log=None).serve_forever()
The segfault occurs in pyscopg2 C code. When the make_psycopg_green() call is commented out, no segfault occurs and operation is as expected, though of course psycopg2 calls are synchronous.

The failure only occurs when I am invoking multiple web requests from concurrent clients, which cause multiple greenlets to be spawned to run long-running jobs which invoke psycopg2 through the SQLAlchemy ORM.

Stack trace from core dump using gdb (in case it's any use):

Core was generated by `python gwebapp.py'.
Program terminated with signal 11, Segmentation fault.
    Core was generated by `python gwebapp.py'.
    Program terminated with signal 11, Segmentation fault.
    #0  0x00000000004606a9 in PyDict_SetItem ()
    (gdb) where
    #0  0x00000000004606a9 in PyDict_SetItem ()
    #1  0x0000000000461a48 in PyDict_SetItemString ()
    #2  0x00007fc172da98ba in psyco_error_reduce (self=0x25fb1b8)
        at psycopg/error_type.c:166
    #3  0x000000000041ad4a in PyObject_Call ()
    #4  0x00000000004b5ed6 in PyEval_CallObjectWithKeywords ()
    #5  0x000000000047c457 in ?? ()
    #6  0x000000000041ad4a in PyObject_Call ()
    #7  0x0000000000526f8e in ?? ()
    #8  0x00000000005291d6 in ?? ()
    #9  0x00000000005276c3 in ?? ()
    #10 0x00000000005270f3 in ?? ()
    #11 0x00000000005291d6 in ?? ()
    #12 0x00000000005276c3 in ?? ()
    #13 0x00000000005277c4 in ?? ()
    #14 0x00000000005288d3 in ?? ()
    #15 0x00000000005289a5 in ?? ()
    #16 0x00000000004b66b9 in PyEval_EvalFrameEx ()
    #17 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #18 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #19 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #20 0x000000000044914f in ?? ()
    #21 0x000000000041ad4a in PyObject_Call ()
    #22 0x000000000043092e in ?? ()
    #23 0x000000000041ad4a in PyObject_Call ()
    #24 0x00000000004b6d7e in PyEval_EvalFrameEx ()
    #25 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #26 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #27 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #28 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #29 0x0000000000449308 in ?? ()
    #30 0x000000000041ad4a in PyObject_Call ()
    #31 0x00000000004b8498 in PyEval_EvalFrameEx ()
    #32 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #33 0x0000000000449308 in ?? ()
    #34 0x000000000041ad4a in PyObject_Call ()
    #35 0x00000000004b8498 in PyEval_EvalFrameEx ()
    #36 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #37 0x00000000004b6c34 in PyEval_EvalFrameEx ()
    #38 0x00000000004bd3ee in PyEval_EvalCodeEx ()
    #39 0x0000000000449308 in ?? ()
    #40 0x000000000041ad4a in PyObject_Call ()
    #41 0x00000000004b8498 in PyEval_EvalFrameEx ()
    #42 0x00000000004bd3ee in PyEval_EvalCodeEx ()
    #43 0x0000000000449308 in ?? ()
    #44 0x000000000041ad4a in PyObject_Call ()
    #45 0x00000000004b8498 in PyEval_EvalFrameEx ()
    #46 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #47 0x00000000004b6c34 in PyEval_EvalFrameEx ()
    #48 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #49 0x00000000004b6c34 in PyEval_EvalFrameEx ()
    #50 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #51 0x000000000044914f in ?? ()
    #52 0x000000000041ad4a in PyObject_Call ()
    #53 0x000000000043092e in ?? ()
    #54 0x000000000041ad4a in PyObject_Call ()
    #55 0x0000000000480716 in ?? ()
    #56 0x000000000041ad4a in PyObject_Call ()
    #57 0x00000000004b6d7e in PyEval_EvalFrameEx ()
    #58 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #59 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #60 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #61 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #62 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #63 0x0000000000449308 in ?? ()
    #64 0x000000000041ad4a in PyObject_Call ()
    #65 0x00000000004b8498 in PyEval_EvalFrameEx ()
    #66 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #67 0x0000000000449308 in ?? ()
    #68 0x000000000041ad4a in PyObject_Call ()
    #69 0x000000000043092e in ?? ()
    #70 0x000000000041ad4a in PyObject_Call ()
    #71 0x00000000004b5ed6 in PyEval_CallObjectWithKeywords ()
    #72 0x00007fc17329ea56 in g_initialstub (mark=<optimized out>)
        at greenlet.c:804
    #73 0x00007fc17329e398 in g_switch (target=0x1875f50, args=0x7fc175e66050, 
        kwargs=0x3741130) at greenlet.c:576
    #74 0x00007fc17329ef26 in green_switch (self=<optimized out>, 
        args=<optimized out>, kwargs=<optimized out>) at greenlet.c:1092
    #75 0x000000000041ad4a in PyObject_Call ()
    #76 0x00007fc17390b3f3 in __pyx_f_6gevent_4core___simple_handler (
        __pyx_v_fd=<optimized out>, __pyx_v_evtype=<optimized out>, 
        __pyx_v_arg=0x3eb1488) at gevent/core.c:5130
    #77 0x00007fc1736b8d3c in event_base_loop () from /usr/lib/libevent-2.0.so.5
    #78 0x00007fc1738fe105 in __pyx_pf_6gevent_4core_2dispatch (
        __pyx_self=<optimized out>) at gevent/core.c:6083
    #79 __pyx_pw_6gevent_4core_3dispatch (__pyx_self=<optimized out>, 
        unused=<optimized out>) at gevent/core.c:6036
    #80 0x00000000004b7281 in PyEval_EvalFrameEx ()
    #81 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #82 0x000000000044914f in ?? ()
    #83 0x000000000041ad4a in PyObject_Call ()
    #84 0x000000000043092e in ?? ()
    #85 0x000000000041ad4a in PyObject_Call ()
    #86 0x00000000004b5ed6 in PyEval_CallObjectWithKeywords ()
    #87 0x00007fc17329ea56 in g_initialstub (mark=<optimized out>)
        at greenlet.c:804
    #88 0x00007fc17329e398 in g_switch (target=0x25f7050, args=0x7fc175e66050, 
        kwargs=0x0) at greenlet.c:576
    #89 0x00007fc17329ef26 in green_switch (self=<optimized out>, 
        args=<optimized out>, kwargs=<optimized out>) at greenlet.c:1092
    #90 0x000000000041ad4a in PyObject_Call ()
    #91 0x00000000004b5ed6 in PyEval_CallObjectWithKeywords ()
    #92 0x00000000004399a7 in ?? ()
    #93 0x000000000041ad4a in PyObject_Call ()
    #94 0x00000000004b6d7e in PyEval_EvalFrameEx ()
    #95 0x00000000004b6f57 in PyEval_EvalFrameEx ()
    #96 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #97 0x00000000004b6c34 in PyEval_EvalFrameEx ()
    #98 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #99 0x00000000004b6c34 in PyEval_EvalFrameEx ()
    #100 0x00000000004bcdbd in PyEval_EvalCodeEx ()
    #101 0x00000000004bd892 in PyEval_EvalCode ()
    #102 0x00000000004dcd82 in ?? ()
    #103 0x00000000004dd974 in PyRun_FileExFlags ()

tagged:rel-2.2.1
tagged:os-linux
tagged:gevent

Comments and changes to this ticket

  • Daniele Varrazzo

    Daniele Varrazzo October 2nd, 2013 @ 04:06 PM

    • State changed from “new” to “resolved”

    It's in the exception pickling: I think it's caused by bug #170

    Core was generated by `python gwebapp.py'.
    Program terminated with signal 11, Segmentation fault.
    [#0](/projects/62710/tickets/0 "Ticket #0")  0x00000000004606a9 in PyDict_SetItem ()
    (gdb) where
    [#0](/projects/62710/tickets/0 "Ticket #0")  0x00000000004606a9 in PyDict_SetItem ()
    [#1](/projects/62710/tickets/1 "Ticket #1")  0x0000000000461a48 in PyDict_SetItemString ()
    [#2](/projects/62710/tickets/2 "Ticket #2")  0x00007fc172da98ba in psyco_error_reduce (self=0x25fb1b8)
        at psycopg/error_type.c:166
    

    It was fixed but not released yet. Do you want to test with that patch on?

    I think we'll need a release soonish.

  • Vinay Sajip

    Vinay Sajip October 2nd, 2013 @ 05:08 PM

    I can confirm that with your code from the master branch of https://github.com/dvarrazzo/psycopg, the segfault goes away. Thanks!

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