[poppler] XRef::fetch mutex lock

Sat Apr 6 09:26:52 PDT 2013

Hi Albert & Adam!

Great work. I think we are quite close now to have a working, testable, 
stable and maintainable solution for multi threading.

Cheers,
Thomas

Am 06.04.2013 17:19, schrieb Albert Astals Cid:
> El Dimarts, 2 d'abril de 2013, a les 10:36:53, Thomas Freitag va escriure:
>> Am 02.04.2013 09:22, schrieb Thomas Freitag:
>>> Hi Albert!
>>>
>>> Am 27.03.2013 12:29, schrieb Thomas Freitag:
>>>> Sorry, pushed the wrong button, here my answer to the list:
>>>>
>>>> Am 27.03.2013 11:41, schrieb Albert Astals Cid:
>>>>> Why do we pass around the recursion integer around?
>>>> No idea: The recursive integer wasn't introduced by the thread safe
>>>> patch, it was already there. I just used it and extend some functions
>>>> which incorrectly ignore that parameter instead of passing it to the
>>>> called functions. Probably I missed some more than only the one in
>>>> DCTStream::DCTStream.
>>> I just ran a regression test over my PDF files, but I didn't get any
>>> dead locks. So if You want me to solve that problem, You should
>>> provide me that PDF. (Regardless if You prefer to use recursive mutex:
>>> the endless loop detection need to pass the recursive integer
>>> everywhere!)
>> Attached a patch which corrects it. I made it in my sleep, 'cause the
>> dead lock was probably caused by my patch for bug 61994 (even if that
>> PDF doesn't cause any dead locks). This time I also respect the
>> DCTStream usage if LIBJPEG is disabled :-)
> Commited this one too in addition to the recursive mutex one.
>
> Cheers,
>    Albert
>
>> Cheers,
>> Thomas
>>
>>> Cheers,
>>> Thomas
>>>
>>>>> Wouldn't a real recursive mutex be enough?
>>>> No idea: I used in the thread safe patch just the pthread_lock which
>>>> was defined. I'm not knowing what happens when we change it globally
>>>> i.e. if it affects other usages of the GooMutex. Just feel free to
>>>> change it, You should have the better overview of usages than I have.
>>>>
>>>> Cheers,
>>>> Thomas
>>>>
>>>>> I'm asking because i have a document here (that sadly i can't share)
>>>>> that is deadlocking
>>>>> itself there because we are not passing the recursion integer
>>>>> everywhere (we lose it in DCTStream::DCTStream)
>>>>> as shown in this backtrace
>>>>>
>>>>> #0  __lll_lock_wait () at
>>>>> ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
>>>>> #1  0x00007ffff599217c in _L_lock_982 () from
>>>>> /lib/x86_64-linux-gnu/libpthread.so.0
>>>>> #2  0x00007ffff5991fcb in __GI___pthread_mutex_lock (mutex=0x71dc10)
>>>>> at pthread_mutex_lock.c:64
>>>>> #3  0x00007ffff5f02f73 in MutexLocker::MutexLocker
>>>>> (this=0x7fffffffcfb0, mutexA=0x71dc10, modeA=DoLockMutex) at
>>>>> /home/tsdgeos/devel/poppler/goo/GooMutex.h:72
>>>>> #4  0x00007ffff5fac8e2 in XRef::fetch (this=0x71db50, num=5, gen=0,
>>>>> obj=0x7fffffffd0b0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/XRef.cc:1137
>>>>> #5  0x00007ffff5f8a013 in Object::fetch (this=0x71fe08,
>>>>> xref=0x71db50, obj=0x7fffffffd0b0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Object.cc:122
>>>>> #6  0x00007ffff5f19de4 in Dict::lookup (this=0x71fb60,
>>>>> key=0x7ffff606fbba "Height", obj=0x7fffffffd0b0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Dict.cc:256
>>>>> #7  0x00007ffff5f032e9 in Object::dictLookup (this=0x7fffffffd5a0,
>>>>> key=0x7ffff606fbba "Height", obj=0x7fffffffd0b0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Object.h:315
>>>>> #8  0x00007ffff601f8a3 in DCTStream::DCTStream (this=0x7832b0,
>>>>> strA=0x720780, colorXformA=-1, dict=0x7fffffffd5a0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/DCTStream.cc:72
>>>>> #9  0x00007ffff5f9bf6d in Stream::makeFilter (this=0x720780,
>>>>> name=0x71fef0 "DCTDecode", str=0x720780, params=0x7fffffffd1e0,
>>>>> recursion=1, dict=0x7fffffffd5a0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Stream.cc:311
>>>>> #10 0x00007ffff5f9b71a in Stream::addFilters (this=0x720780,
>>>>> dict=0x7fffffffd5a0, recursion=1) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Stream.cc:184
>>>>> #11 0x00007ffff5f9204b in Parser::makeStream (this=0x71fcd0,
>>>>> dict=0x7fffffffd5a0, fileKey=0x0, encAlgorithm=cryptRC4,
>>>>> keyLength=1146103040, objNum=3, objGen=0, recursion=1, strict=false)
>>>>> at /home/tsdgeos/devel/poppler/poppler/Parser.cc:280
>>>>> #12 0x00007ffff5f918e6 in Parser::getObj (this=0x71fcd0,
>>>>> obj=0x7fffffffd5a0, simpleOnly=false, fileKey=0x0,
>>>>> encAlgorithm=cryptRC4, keyLength=1146103040, objNum=3, objGen=0,
>>>>> recursion=0, strict=false) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Parser.cc:131
>>>>> #13 0x00007ffff5facdd3 in XRef::fetch (this=0x71db50, num=3, gen=0,
>>>>> obj=0x7fffffffd5a0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/XRef.cc:1197
>>>>> #14 0x00007ffff5f8a013 in Object::fetch (this=0x71e128,
>>>>> xref=0x71db50, obj=0x7fffffffd5a0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Object.cc:122
>>>>> #15 0x00007ffff5f19de4 in Dict::lookup (this=0x71e660, key=0x7206e0
>>>>> "Im1", obj=0x7fffffffd5a0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Dict.cc:256
>>>>> #16 0x00007ffff5f032e9 in Object::dictLookup (this=0x71e598,
>>>>> key=0x7206e0 "Im1", obj=0x7fffffffd5a0, recursion=0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Object.h:315
>>>>> #17 0x00007ffff5f2a647 in GfxResources::lookupXObject
>>>>> (this=0x71e590, name=0x7206e0 "Im1", obj=0x7fffffffd5a0) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Gfx.cc:411
>>>>> #18 0x00007ffff5f3f41e in Gfx::opXObject (this=0x71e440,
>>>>> args=0x7fffffffd720, numArgs=1) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Gfx.cc:4114
>>>>> #19 0x00007ffff5f2bfd6 in Gfx::execOp (this=0x71e440,
>>>>> cmd=0x7fffffffd6e0, args=0x7fffffffd720, numArgs=1) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Gfx.cc:858
>>>>> #20 0x00007ffff5f2b82b in Gfx::go (this=0x71e440, topLevel=true) at
>>>>> /home/tsdgeos/devel/poppler/poppler/Gfx.cc:717
>>>>>
>>>>>
>>>>> Cheers,
>>>>>
>>>>>     Albert
>>>>>
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>>>>>
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