Re: When is it safe to call PyStackless_Schedule

Kristján Valur Jónsson <[email protected]> Wed, 10 Sep 2014 09:02:17 +0000
Newsgroups gmane.comp.python.stackless
Message-ID <CAP8kY6aJQ5y4agOy+tw9jxNBqN5PZnBrDN6oU35Sa+CygKk3vg@mail.gmail.com>
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I suspect that the raw input hook is called without the GIL held.
You need to add a call to
PyGIL_Ensure / PyGIL_Release

On 10 September 2014 05:02, Richard Tew <[email protected]> wrote:

> Hard switching immediately switches by changing the stack contents.
> And soft switching has the function you call return an unwind token
> which should be propagated back through the call chain to the
> scheduler.  If you ignore this, and throw it away, it has caused crash
> problems in the past.  Of course, with the approach you've taken,
> there's no way it can be returned out of that event and back through
> the call chain.  You can try and call the versions of the api which do
> not soft switch, these might be documented in the documentation.
>
> Cheers,
> Richard.
>
> On 9/10/14, Robert Babiak <[email protected]> wrote:
> > oh the actual break message
> >
> > Process 53817 stopped
> >
> > * thread #5: tid = 0x1c027f, 0x0000000100ea30a3
> Python`PyStackless_Schedule
> > + 51, stop reason = EXC_BAD_ACCESS (code=1, address=0xd8)
> >
> >     frame #0: 0x0000000100ea30a3 Python`PyStackless_Schedule + 51
> >
> > Python`PyStackless_Schedule + 51:
> >
> > -> 0x100ea30a3:  movq   0xd8(%r13), %rbx
> >
> >    0x100ea30aa:  movq   0x10(%rbx), %r12
> >
> >    0x100ea30ae:  movq   $0x0, -0x30(%rbp)
> >
> >    0x100ea30b6:  cmpq   $0x0, 0xd0(%r13)
> >
> > On Tue, Sep 9, 2014 at 9:57 PM, Robert Babiak <[email protected]> wrote:
> >
> >> I took the Receive out and replaced it with a simple call to
> >> PyStackless_Schedule.
> >>
> >> static int EventHook(void)
> >> {
> >>     PyStackless_Schedule(Py_None, 0);
> >>     return 0;
> >> }
> >> ...
> >>         Py_SetProgramName(argv[0]);
> >>         Py_InitializeEx(0);
> >>         if (!Py_IsInitialized())
> >>         {
> >>             std::cerr << "Python initialization failed" << std::endl;
> >>             return;
> >>         }
> >>         PySys_SetArgv(argc, argv);
> >>         PyOS_InputHook = EventHook;
> >> ...
> >>         // stacklessMain returns when program is shutdown.
> >>         PyStackless_CallMethod_Main(oMainModule.ptr(), "stacklessMain",
> >> 0);
> >> ...
> >>
> >> This is the lldb stacktrace
> >>
> >> frame #0: 0x0000000100ea30a3 Python`PyStackless_Schedule + 51
> >>
> >>  frame #1: 0x0000000100155fd9 main`EventHook() + 25 at
> >> pythonInterperter.cpp:472
> >>
> >>     frame #2: 0x0000000103dd5e25 readline.so`call_readline + 293
> >>
> >>     frame #3: 0x0000000100dfa3c3 Python`PyOS_Readline + 179
> >>
> >>     frame #4: 0x0000000100e92882 Python`builtin_raw_input + 434
> >>
> >>     frame #5: 0x0000000100e95d88 Python`PyEval_EvalFrame_value + 3832
> >>
> >>     frame #6: 0x0000000100e94d38 Python`PyEval_EvalFrameEx_slp + 376
> >>
> >>     frame #7: 0x0000000100e9744c Python`PyEval_EvalFrame_value + 9660
> >>
> >>     frame #8: 0x0000000100e94d38 Python`PyEval_EvalFrameEx_slp + 376
> >>
> >>     frame #9: 0x0000000100e9744c Python`PyEval_EvalFrame_value + 9660
> >>
> >>     frame #10: 0x0000000100e94d38 Python`PyEval_EvalFrameEx_slp + 376
> >>
> >>     frame #11: 0x0000000100e9e9e1 Python`slp_frame_dispatch_top + 49
> >>
> >>     frame #12: 0x0000000100ea2772 Python`slp_run_tasklet + 226
> >>
> >>     frame #13: 0x0000000100e9e0fc Python`slp_eval_frame + 348
> >>
> >>     frame #14: 0x0000000100e9e083 Python`slp_eval_frame + 227
> >>
> >>     frame #15: 0x0000000100e9e083 Python`slp_eval_frame + 227
> >>
> >> .....
> >>
> >>     frame #719: 0x0000000100e9e083 Python`slp_eval_frame + 227
> >>
> >>     frame #720: 0x0000000100e9e083 Python`slp_eval_frame + 227
> >>
> >>     frame #721: 0x0000000100ea3801 Python`PyStackless_CallMethod_Main +
> >> 433
> >>
> >>     frame #722: 0x00000001001588e3
> >> main`PythonThread::operator(this=0x0000000101506940)() + 1187 at
> >> pythonInterperter.cpp:555
> >>
> >>     frame #723: 0x000000010015761c
> >>
> main`boost::detail::thread_data<PythonThread>::run(this=0x0000000101506740)
> >> + 28 at thread.hpp:117
> >>
> >>     frame #724: 0x00000001010ff24a libboost_thread-mt.dylib`thread_proxy
> >> +
> >> 186
> >>
> >>     frame #725: 0x00007fff863fb899 libsystem_pthread.dylib`_pthread_body
> >> +
> >> 138
> >>
> >>     frame #726: 0x00007fff863fb72a
> libsystem_pthread.dylib`_pthread_start
> >> + 137
> >>
> >> On Tue, Sep 9, 2014 at 9:17 PM, Richard Tew <[email protected]>
> >> wrote:
> >>
> >>> If you have a crash when you call receive, then you likely have larger
> >>> problems than when the right time to call schedule is.
> >>>
> >>> I don't think it's possible to divine what is going wrong, and expect
> >>> you need to provide a reproduction case.
> >>>
> >>> Cheers
> >>>
> >>> On 9/10/14, Robert Babiak <[email protected]> wrote:
> >>> > Dear wise stackless list, I need some of your wisdom.
> >>> >
> >>> > I am trying to make raw_input play nice with the stackless scheduler
> >>> > and
> >>> > not block with my embedded stackless.
> >>> >
> >>> > I set the PyOS_InputHook to get what amounts to an idle event but
> when
> >>> > I
> >>> > call PyStackless_Schedule(PY_None, 0) it crashes (no stackless
> >>> symbols...)
> >>> >
> >>> > Is there something I need to check to know if it is safe to call the
> >>> > scheduler from C?
> >>> >
> >>> > In general when is it safe to call  PyStackless_Schedule?
> >>> >
> >>> > I tried to call my BeNice to block and get woken up later, but this
> >>> > also
> >>> > crashes when trying to receive on my BeNice channel.
> >>> >
> >>> > - Thanks Rob.
> >>> > --
> >>> > Life: Bah, I will worry about it when it is over.
> >>> >
> >>>
> >>> _______________________________________________
> >>> Stackless mailing list
> >>> [email protected]
> >>> http://www.stackless.com/mailman/listinfo/stackless
> >>>
> >>
> >>
> >>
> >> --
> >> Life: Bah, I will worry about it when it is over.
> >>
> >
> >
> >
> > --
> > Life: Bah, I will worry about it when it is over.
> >
>
> _______________________________________________
> Stackless mailing list
> [email protected]
> http://www.stackless.com/mailman/listinfo/stackless
>

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<div dir=3D"ltr">I suspect that the raw input hook is called without the GI=
L held.<div>You need to add a call to=C2=A0</div><div>PyGIL_Ensure / PyGIL_=
Release</div></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote=
">On 10 September 2014 05:02, Richard Tew <span dir=3D"ltr">&lt;<a href=3D"=
mailto:[email protected]" target=3D"_blank">[email protected]</=
a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0=
 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hard switching immed=
iately switches by changing the stack contents.<br>
And soft switching has the function you call return an unwind token<br>
which should be propagated back through the call chain to the<br>
scheduler.=C2=A0 If you ignore this, and throw it away, it has caused crash=
<br>
problems in the past.=C2=A0 Of course, with the approach you&#39;ve taken,<=
br>
there&#39;s no way it can be returned out of that event and back through<br=
>
the call chain.=C2=A0 You can try and call the versions of the api which do=
<br>
not soft switch, these might be documented in the documentation.<br>
<br>
Cheers,<br>
Richard.<br>
<div class=3D"HOEnZb"><div class=3D"h5"><br>
On 9/10/14, Robert Babiak &lt;<a href=3D"mailto:[email protected]">rbabiak@=
gmail.com</a>&gt; wrote:<br>
&gt; oh the actual break message<br>
&gt;<br>
&gt; Process 53817 stopped<br>
&gt;<br>
&gt; * thread #5: tid =3D 0x1c027f, 0x0000000100ea30a3 Python`PyStackless_S=
chedule<br>
&gt; + 51, stop reason =3D EXC_BAD_ACCESS (code=3D1, address=3D0xd8)<br>
&gt;<br>
&gt;=C2=A0 =C2=A0 =C2=A0frame #0: 0x0000000100ea30a3 Python`PyStackless_Sch=
edule + 51<br>
&gt;<br>
&gt; Python`PyStackless_Schedule + 51:<br>
&gt;<br>
&gt; -&gt; 0x100ea30a3:=C2=A0 movq=C2=A0 =C2=A00xd8(%r13), %rbx<br>
&gt;<br>
&gt;=C2=A0 =C2=A0 0x100ea30aa:=C2=A0 movq=C2=A0 =C2=A00x10(%rbx), %r12<br>
&gt;<br>
&gt;=C2=A0 =C2=A0 0x100ea30ae:=C2=A0 movq=C2=A0 =C2=A0$0x0, -0x30(%rbp)<br>
&gt;<br>
&gt;=C2=A0 =C2=A0 0x100ea30b6:=C2=A0 cmpq=C2=A0 =C2=A0$0x0, 0xd0(%r13)<br>
&gt;<br>
&gt; On Tue, Sep 9, 2014 at 9:57 PM, Robert Babiak &lt;<a href=3D"mailto:rb=
[email protected]">[email protected]</a>&gt; wrote:<br>
&gt;<br>
&gt;&gt; I took the Receive out and replaced it with a simple call to<br>
&gt;&gt; PyStackless_Schedule.<br>
&gt;&gt;<br>
&gt;&gt; static int EventHook(void)<br>
&gt;&gt; {<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0PyStackless_Schedule(Py_None, 0);<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0return 0;<br>
&gt;&gt; }<br>
&gt;&gt; ...<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Py_SetProgramName(argv[0]);<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Py_InitializeEx(0);<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0if (!Py_IsInitialized())<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0{<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0std::cerr &lt;&lt; =
&quot;Python initialization failed&quot; &lt;&lt; std::endl;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0}<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0PySys_SetArgv(argc, argv);<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0PyOS_InputHook =3D EventHook;<br>
&gt;&gt; ...<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0// stacklessMain returns when pro=
gram is shutdown.<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0PyStackless_CallMethod_Main(oMain=
Module.ptr(), &quot;stacklessMain&quot;,<br>
&gt;&gt; 0);<br>
&gt;&gt; ...<br>
&gt;&gt;<br>
&gt;&gt; This is the lldb stacktrace<br>
&gt;&gt;<br>
&gt;&gt; frame #0: 0x0000000100ea30a3 Python`PyStackless_Schedule + 51<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 frame #1: 0x0000000100155fd9 main`EventHook() + 25 at<br>
&gt;&gt; pythonInterperter.cpp:472<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #2: 0x0000000103dd5e25 readline.so`call_r=
eadline + 293<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #3: 0x0000000100dfa3c3 Python`PyOS_Readli=
ne + 179<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #4: 0x0000000100e92882 Python`builtin_raw=
_input + 434<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #5: 0x0000000100e95d88 Python`PyEval_Eval=
Frame_value + 3832<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #6: 0x0000000100e94d38 Python`PyEval_Eval=
FrameEx_slp + 376<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #7: 0x0000000100e9744c Python`PyEval_Eval=
Frame_value + 9660<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #8: 0x0000000100e94d38 Python`PyEval_Eval=
FrameEx_slp + 376<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #9: 0x0000000100e9744c Python`PyEval_Eval=
Frame_value + 9660<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #10: 0x0000000100e94d38 Python`PyEval_Eva=
lFrameEx_slp + 376<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #11: 0x0000000100e9e9e1 Python`slp_frame_=
dispatch_top + 49<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #12: 0x0000000100ea2772 Python`slp_run_ta=
sklet + 226<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #13: 0x0000000100e9e0fc Python`slp_eval_f=
rame + 348<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #14: 0x0000000100e9e083 Python`slp_eval_f=
rame + 227<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #15: 0x0000000100e9e083 Python`slp_eval_f=
rame + 227<br>
&gt;&gt;<br>
&gt;&gt; .....<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #719: 0x0000000100e9e083 Python`slp_eval_=
frame + 227<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #720: 0x0000000100e9e083 Python`slp_eval_=
frame + 227<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #721: 0x0000000100ea3801 Python`PyStackle=
ss_CallMethod_Main +<br>
&gt;&gt; 433<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #722: 0x00000001001588e3<br>
&gt;&gt; main`PythonThread::operator(this=3D0x0000000101506940)() + 1187 at=
<br>
&gt;&gt; pythonInterperter.cpp:555<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #723: 0x000000010015761c<br>
&gt;&gt; main`boost::detail::thread_data&lt;PythonThread&gt;::run(this=3D0x=
0000000101506740)<br>
&gt;&gt; + 28 at thread.hpp:117<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #724: 0x00000001010ff24a libboost_thread-=
mt.dylib`thread_proxy<br>
&gt;&gt; +<br>
&gt;&gt; 186<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #725: 0x00007fff863fb899 libsystem_pthrea=
d.dylib`_pthread_body<br>
&gt;&gt; +<br>
&gt;&gt; 138<br>
&gt;&gt;<br>
&gt;&gt;=C2=A0 =C2=A0 =C2=A0frame #726: 0x00007fff863fb72a libsystem_pthrea=
d.dylib`_pthread_start<br>
&gt;&gt; + 137<br>
&gt;&gt;<br>
&gt;&gt; On Tue, Sep 9, 2014 at 9:17 PM, Richard Tew &lt;<a href=3D"mailto:=
[email protected]">[email protected]</a>&gt;<br>
&gt;&gt; wrote:<br>
&gt;&gt;<br>
&gt;&gt;&gt; If you have a crash when you call receive, then you likely hav=
e larger<br>
&gt;&gt;&gt; problems than when the right time to call schedule is.<br>
&gt;&gt;&gt;<br>
&gt;&gt;&gt; I don&#39;t think it&#39;s possible to divine what is going wr=
ong, and expect<br>
&gt;&gt;&gt; you need to provide a reproduction case.<br>
&gt;&gt;&gt;<br>
&gt;&gt;&gt; Cheers<br>
&gt;&gt;&gt;<br>
&gt;&gt;&gt; On 9/10/14, Robert Babiak &lt;<a href=3D"mailto:rbabiak@gmail.=
com">[email protected]</a>&gt; wrote:<br>
&gt;&gt;&gt; &gt; Dear wise stackless list, I need some of your wisdom.<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt; &gt; I am trying to make raw_input play nice with the stackles=
s scheduler<br>
&gt;&gt;&gt; &gt; and<br>
&gt;&gt;&gt; &gt; not block with my embedded stackless.<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt; &gt; I set the PyOS_InputHook to get what amounts to an idle e=
vent but when<br>
&gt;&gt;&gt; &gt; I<br>
&gt;&gt;&gt; &gt; call PyStackless_Schedule(PY_None, 0) it crashes (no stac=
kless<br>
&gt;&gt;&gt; symbols...)<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt; &gt; Is there something I need to check to know if it is safe =
to call the<br>
&gt;&gt;&gt; &gt; scheduler from C?<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt; &gt; In general when is it safe to call=C2=A0 PyStackless_Sche=
dule?<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt; &gt; I tried to call my BeNice to block and get woken up later=
, but this<br>
&gt;&gt;&gt; &gt; also<br>
&gt;&gt;&gt; &gt; crashes when trying to receive on my BeNice channel.<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt; &gt; - Thanks Rob.<br>
&gt;&gt;&gt; &gt; --<br>
&gt;&gt;&gt; &gt; Life: Bah, I will worry about it when it is over.<br>
&gt;&gt;&gt; &gt;<br>
&gt;&gt;&gt;<br>
&gt;&gt;&gt; _______________________________________________<br>
&gt;&gt;&gt; Stackless mailing list<br>
&gt;&gt;&gt; <a href=3D"mailto:[email protected]">Stackless@stackless=
.com</a><br>
&gt;&gt;&gt; <a href=3D"http://www.stackless.com/mailman/listinfo/stackless=
" target=3D"_blank">http://www.stackless.com/mailman/listinfo/stackless</a>=
<br>
&gt;&gt;&gt;<br>
&gt;&gt;<br>
&gt;&gt;<br>
&gt;&gt;<br>
&gt;&gt; --<br>
&gt;&gt; Life: Bah, I will worry about it when it is over.<br>
&gt;&gt;<br>
&gt;<br>
&gt;<br>
&gt;<br>
&gt; --<br>
&gt; Life: Bah, I will worry about it when it is over.<br>
&gt;<br>
<br>
_______________________________________________<br>
Stackless mailing list<br>
<a href=3D"mailto:[email protected]">[email protected]</a><br>
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blank">http://www.stackless.com/mailman/listinfo/stackless</a><br>
</div></div></blockquote></div><br></div>

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