irclog2html for #brlcad on 20061204

01:01.00 Maloeran I know I have whined about this before, but the C parser of Doxygen sure is broken on many points
01:02.07 Twingy but Lee sure seems to love it
01:02.18 Maloeran Arrays of function pointers are functions, struct variables with gnu99 __attribute__ are "class methods" ( hello, this is C )
01:03.14 Maloeran It's nice on some aspects, but the parser makes some gross mistakes
01:07.43 Maloeran Whenever the data type of something is complex, it thinks it's a function or a method. Oh, and I had Doxygen tell me that for(;;) and if() where undocumented "functions" before
01:11.06 ``Erik nice
01:11.21 ``Erik if only for() and if() WERE functions in C
01:11.22 ``Erik *sigh*
01:12.40 Maloeran Lisp is nice, but I'm not against having some fundamental language contructs that are not functions
01:35.56 ``Erik http://www.calarts.edu/~jwhite/gbj/SeeHim.html
01:36.10 ``Erik lithp and thcheme have language constructs that aren't functions
07:08.23 *** join/#brlcad clock_ (i=clock@84-72-60-30.dclient.hispeed.ch)
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16:51.15 brlcad ``Erik: you have any 6.2 discs burnt?
17:18.03 ``Erik uhmmmmmmmm, no, 6.2 isn't released yet
17:18.21 ``Erik it's rc1
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18:36.22 ``Erik mal: fixes rendering, yup, but generation is still effed up
18:36.32 ``Erik linux 8core amd64...
18:36.33 ``Erik linkListAddPair (listhead0=0x2a95d3a668, listhead1=0x2a95bfe290, step0=0x2a95d3a618, step1=0x2a95bfe238, memblock=0x513bf0) at ../../../RF/prepmodel.c:718
18:36.34 ``Erik 718 if( ( linklist1->used == LINKS_PER_LIST ) ) {
18:36.34 ``Erik (gdb) print *linklist1
18:36.34 ``Erik Cannot access memory at address 0x0
18:37.02 ``Erik (and fbsd just sits, no crash)
18:40.45 Maloeran Okay, every time or sometimes?
18:42.52 Maloeran And fbsd freezes constantly or it's less consistant? I'm just trying to get an idea of what's going on
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18:44.06 ``Erik linux:
18:44.07 ``Erik 0x0000002a9585ba41 in jobModelPrepStep (engine=0x50aa20, job=Variable "job" is not available.
18:44.07 ``Erik ) at ../../../RF/prepmodel.c:1720
18:44.07 ``Erik 1720 if( steplink->edge[axismin] < plane ) {
18:44.47 Maloeran Right okay, not too consistent, though I guess it does crash pretty much all the time
18:45.19 Maloeran And always in the same pass, okay
18:46.18 ``Erik if there's a valid cache, it's all grand... gettin' ~40fps on both the 4 core fbsd and the 8 core linux (hardcoded at 4 threads, I guess)
18:46.58 ``Erik hah, linux: Can't attach LWP -1023750857: No such process
18:47.10 ``Erik fbsd seems stuck
18:47.11 Maloeran Yes, fix rfdemo.c to increase that count, hard-coded #define
18:47.21 Maloeran No such process, eh? :)
18:48.47 Maloeran I guess I now have some information to figure out this bug
18:50.22 Maloeran The more backtrace you can throw at me, the easier I think it would be to see what's happening in there
18:51.17 ``Erik 0x0000002a9585ad7f in jobModelPrepEvaluate (engine=0xc4f5d489c4f61b90, job=Variable "job" is not available.
18:51.17 ``Erik ) at ../../../RF/prepmodel.c:974
18:51.17 ``Erik 974 } while( --a );
18:51.19 ``Erik wonky
18:51.32 ``Erik bt on that is a blown stack
18:51.53 Maloeran Groovy
18:52.55 ``Erik meh, paste.lisp.org seems to be down
18:53.06 Maloeran rafb.net/paste of course
18:53.17 ``Erik <-- coudln't remember the url
18:56.10 ``Erik http://rafb.net/paste/results/kONUFQ20.html
18:56.24 ``Erik those seem to be the 4 cases I get on linux 2.6 amd64
18:56.51 Maloeran Great, thank you
18:56.56 ``Erik np
18:57.10 ``Erik I have a 2 hour meeting starting in 30 minutes...
18:57.51 Maloeran :) Have fun!
19:00.16 ``Erik heh
19:00.34 ``Erik just letting you know in case you have any modifications you want to see run on multi-cache machines
19:01.56 ``Erik hrm, I'm going to try to bump the thread count to something a bit more straining... hope that linux doesn't drop the ball on it... I know it's ok on fbsd and solaris
19:02.25 ``Erik heh, gdb might be the problem here :)
19:04.07 ``Erik goddamn, it's slugging down ugly :(
19:11.06 ``Erik http://rafb.net/paste/results/wJKR5372.html <-- new error
19:11.10 ``Erik 128 threads
19:11.28 ``Erik that the 'job' variable is unavailable on all the errors is... suspicious
19:19.29 Maloeran New error, always the same pass, and consistent with a corruption of the lists of reverse links
19:20.06 Maloeran 128 threads, I haven't tried that yet :). I think I can figure out what's going on, the problem has been narrowed a bit
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22:31.01 brlcad looks like Maloeran needs some valgrindage
22:31.37 Maloeran I can't reproduce the bug, it's of no use ;)
22:31.55 brlcad valgrind will still report the memory problems
22:32.36 brlcad assuming it's not a platformness but actually just problem being masked by linux behavior
22:33.10 Maloeran It's a problem caused by multiple cores not shared the same cache, probably a faulty mutex somewhere
22:33.19 brlcad valgrind is very good in what it does, way better than the memory bounds checkers
22:34.36 Maloeran Indeed, I'm just skeptical on its ability to catch a bug that requires multiple caches to occur
22:34.52 Maloeran Anyway. If I haven't solved this by tomorrow, I'll call a friend to ask to boot his 4 cores desktop on Linux
22:35.53 brlcad you've narrowed it down that far for sure, or guessing? :)
22:36.30 Maloeran I can never reproduce the bug when it is running on a single core, or dual cores but with shared cache
22:36.59 brlcad you mean you can't reproduce the crash
22:38.19 brlcad point being that you could run for years on a single-thread single core machine and never see bad behavior, yet there still be a memory problem (that is simply masked by OS or C lib behavior)
22:38.42 brlcad running gentoo?
22:38.52 Maloeran Of course so, but that memory problem might not be a "problem" in that case just because threads all share the same cache
22:38.55 Maloeran Yes
22:40.58 dtidrow_work gonna get nasty cold around here tonight :-(
22:41.00 Maloeran An unsafe memory instruction might just happen to have a direct memory operand, so you'll never see a problem if threads are executed one at a time on the same cache
22:41.49 Maloeran And no debugger could ever figure that out, unless you trigger the bug with threads running on distinct caches
22:42.22 brlcad you're already assuming that's the bug too (and maybe it is, but it's generally not good to assume when hunting stack corruption)
22:42.45 Maloeran The stack corruption was caused by something else, probably a consequence of the first bug
22:42.51 brlcad easy enough to recompile once, run and get a valgrind report
22:43.11 brlcad comes up clean and then at least basic operation is sound
22:43.43 brlcad if you get lucky, though, it might indicate a problem elsewhere that hadn't even been considered, or thought to be fine
22:44.28 ``Erik heh
22:44.33 Maloeran Syscall param write() points to unitialized bytes in XOpenDisplay() Eheh okay, that was unexpected
22:57.16 Maloeran ( It's not done prep'ing, I think I'll get results before tomorrow )
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23:11.30 Maloeran No error found by Valgrind, unfortunately
23:19.59 ``Erik hum
23:20.16 ``Erik what about grabbing bochs, setting it up as a true smp and grabbing a leenewx smp disk image
23:20.19 ``Erik and see if it can crash in that?
23:20.32 ``Erik (won' be fast, but it might be a way to reproduce the error)
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