[poppler] XRef::fetch mutex lock

[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.
> 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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