You will want to do `handle SIGSEGV nostop noprint` when you start gdb. Racket BC uses the SEGV handler to implement the GC write barrier, so you'll want to skip those.
Sam On Fri, May 8, 2020 at 9:36 AM Dominik Pantůček <dominik.pantu...@trustica.cz> wrote: > > Hello, > > On 08. 05. 20 14:27, Matthew Flatt wrote: > > At Fri, 8 May 2020 09:34:32 +0200, Dominik Pantůček wrote: > >> Apart from obvious strace (after freeze) and gdb (before/after freeze) > >> debugging to find possible sources of this bug, is there even a remote > >> possibility of getting any clue how can this happen based on the > >> information gathered so far? My thought go along the lines: > >> > >> * flonums are boxed - but for some operations they may be immediate > >> * apparently it is a busy-wait loop in RTT, otherwise 100% CPU usage is > >> impossible with this workload > >> * unsafe ops are always suspicious, but again, the problem shows up even > >> when I switch to the safe versions - it just takes longer time > >> * which means, the most probable cause is a race condition > > > > The most useful information here is likely to be a stack trace from > > each OS-level thread at the point where the application is stuck. > > > > That could potentially tell us, for example, that it's a problem with > > synchronization for a GC (where one of the OS threads that run futures > > doesn't cooperate for some reason) or a problem with a the main thread > > performing some specific work on a future thread's behalf. > > > > I am using the build from master branch with the patch for #3145 and > cannot make it run under gdb: > > $ gdb ../racket-lang/racket/racket/bin/racket > GNU gdb (Ubuntu 8.3-0ubuntu1) 8.3 > Copyright (C) 2019 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. > Type "show copying" and "show warranty" for details. > This GDB was configured as "x86_64-linux-gnu". > Type "show configuration" for configuration details. > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > Find the GDB manual and other documentation resources online at: > <http://www.gnu.org/software/gdb/documentation/>. > > For help, type "help". > Type "apropos word" to search for commands related to "word"... > Reading symbols from ../racket-lang/racket/racket/bin/racket... > (No debugging symbols found in ../racket-lang/racket/racket/bin/racket) > (gdb) run > Starting program: > /home/joe/Projects/Programming/racket-lang/racket/racket/bin/racket > [Thread debugging using libthread_db enabled] > Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". > Welcome to Racket v7.7.0.4. > [New Thread 0x7ffff7fcb700 (LWP 6410)] > > Thread 1 "racket" received signal SIGSEGV, Segmentation fault. > 0x00005555555e14fe in scheme_gmp_tls_unload () > (gdb) > > The same happens for the binary with debug symbols: > > gdb ../racket-lang/racket/racket/src/build/racket/racket3m > GNU gdb (Ubuntu 8.3-0ubuntu1) 8.3 > Copyright (C) 2019 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. > Type "show copying" and "show warranty" for details. > This GDB was configured as "x86_64-linux-gnu". > Type "show configuration" for configuration details. > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > Find the GDB manual and other documentation resources online at: > <http://www.gnu.org/software/gdb/documentation/>. > > For help, type "help". > Type "apropos word" to search for commands related to "word"... > Reading symbols from > ../racket-lang/racket/racket/src/build/racket/racket3m... > (gdb) run > Starting program: > /home/joe/Projects/Programming/racket-lang/racket/racket/src/build/racket/racket3m > > [Thread debugging using libthread_db enabled] > Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". > Welcome to Racket v7.7.0.4. > [New Thread 0x7ffff7fcb700 (LWP 6422)] > > Thread 1 "racket3m" received signal SIGSEGV, Segmentation fault. > scheme_gmp_tls_unload (s=0x7ffff6114480, data=0x0) at > ../../../racket/gc2/../src/gmp/gmp.c:5822 > 5822 s[0] = 0; > (gdb) > > I am running Ubuntu 19.10's default gdb: > > $ gdb --version > GNU gdb (Ubuntu 8.3-0ubuntu1) 8.3 > > I assume gmp is used for bignum implementation (didn't check yet), so it > might be relevant as well: > > ii libgmp-dev:amd64 2:6.1.2+dfsg-4 > amd64 Multiprecision arithmetic library > developers tools > ii libgmp10:amd64 2:6.1.2+dfsg-4 > amd64 Multiprecision arithmetic library > ii libgmp10:i386 2:6.1.2+dfsg-4 > i386 Multiprecision arithmetic library > ii libgmpxx4ldbl:amd64 2:6.1.2+dfsg-4 > amd64 Multiprecision arithmetic library (C++ > bindings) > ii python-gmpy:amd64 1.17-4 > amd64 interfaces GMP to Python for fast, > unbound-precision computations > > > I will pull latest master and re-try, but that is really just a blind guess. > > > Cheers, > Dominik > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/01505bda-23c8-c7b0-398a-ad55fe9d4c6c%40trustica.cz. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. 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