Experimental Physics and
Industrial Control System

"Wang Xiaoqiang (PSI)" <[email protected]> · Fri, 15 May 2015 07:46:42 +0000

Hi Michael, Jamie,

Thanks for the hints. In pcaspy library, the PV instances are created on startup and live until application quits.
The casPV::destroy method is not implemented.
https://github.com/paulscherrerinstitute/pcaspy/blob/master/pcaspy/pv.cpp#L112

But it does implement casPV::createChannel for access security group.
Will that cause this double free problem?

Best
Xiaoqiang

> On 13 May 2015, at 23:25, Michael Davidsaver <[email protected]> wrote:
> 
> On 05/13/2015 05:03 PM, Jameson Graef Rollins wrote:
>> ...
>> I think this is just a symlink issue.
> 
> Ok
> 
>> ...  I do however see a
>> "_cas.so" that's included with the pcaspy package [1].
> 
> This is the one I meant.  This all looks normal.
> 
> So I'm 0 for 3 so far :)
> 
>>>> Thread 1 (Thread 0x7f8658d49700 (LWP 26265)):
> ...
>>>> #4  0x00007f86529e2d05 in cantProceed (msg=<optimized out>) at ../../../src/libCom/misc/cantProceed.c:69
>>>> #5  0x00007f8652568525 in casPVI::getExtServer() const () from /ligo/apps/ubuntu12/epics-3.14.12.2_long/base/lib/linux-x86_64/libcas.so.3.14
>>>> #6  0x00007f8652c2efa3 in PV::postEvent (this=0x30a0200, value=...) at pcaspy/pv.cpp:83
>>>> #7  0x00007f8652c1fdc9 in _wrap_PV_postEvent (args=<optimized out>) at pcaspy/casdef_wrap.cpp:9193
>>>> #8  0x0000000000571b58 in PyEval_EvalFrameEx ()
>> 
>> Ok!  So what's to be done here?  Is this a problem in the pcaspy SWIG
>> bindings, or in libcas?  I can't see anything obvious that is being
>> called incorrectly:
> 
> In my experience, when pthread_mutex_unlock fails w/ EINVAL it is either
> a sign of memory corruption, or that the lock has already been free'd
> (w/ pthread_mutex_destory).
> 
> Given that the process doesn't crash I'm guessing its the later.
> 
> Is your application creating, or more importantly destroying, casPVI
> instances when this error appears?  A race during destruction would
> probably explain things.
> 
> 
> Michael
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System