El Dimecres, 3 d'abril de 2013, a les 08:00:34, Thomas Freitag va escriure: > Am 03.04.2013 00:01, 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 :-) > > > > Sure, this fixes the issue (and we should commit it to help with the > > infinite recursion issue), but what's your opinion on making our mutexes > > recursive? > I think, a quite good discussion about recursive and non recursive mutes > was here: > http://stackoverflow.com/questions/187761/recursive-lock-mutex-vs-non-recurs > ive-lock-mutex. This convinced me to vote for a usage of recursive mutex in > poppler: 1. xpdf and therfore poppler wasn't really designed for the usage > of threads. We have it now working, but if we cherish on the usage of non > recursive mutex we will always run into dead lock problems with futur > patches again, so testing patches will become more expensive. > 2. Since poppler nowhere uses emergency exits with "throw", we don't > have the problem that we have to keep track that a thread releases a > mutex so often it aquires it. > 3. The only (small) problem I see is the sentence "Not all systems > supporting pthreads also support recursive mutexes, but if they want to > be POSIX conform, they have to > <http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutexattr_g > ettype.html>."
To be honest i don't think we should care much about the minority of systems there that don't support recursive mutexes. Cheers, Albert > > Cheers, > Thomas > > > It should help us making the code simpler since we could just drop all the > > DoNotLockMutex cases, no? > > > > 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 > >>>>> > >>>>> _______________________________________________ > >>>>> poppler mailing list > >>>>> [email protected] > >>>>> http://lists.freedesktop.org/mailman/listinfo/poppler > >>>>> > >>>>> . > >>>> > >>>> _______________________________________________ > >>>> poppler mailing list > >>>> [email protected] > >>>> http://lists.freedesktop.org/mailman/listinfo/poppler > >>>> > >>>> . > >>> > >>> _______________________________________________ > >>> poppler mailing list > >>> [email protected] > >>> http://lists.freedesktop.org/mailman/listinfo/poppler > >>> > >>> . > > > > _______________________________________________ > > poppler mailing list > > [email protected] > > http://lists.freedesktop.org/mailman/listinfo/poppler > > > > . _______________________________________________ poppler mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/poppler
