[poppler] XRef::fetch mutex lock

Tue Apr 2 01:36:53 PDT 2013

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 :-)

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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>>> poppler at lists.freedesktop.org
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>>>
>>> .
>>>
>>
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