[Openmcl-devel] Random crashing

[Gary Byers]

If you still have the debugging session running, could you do:

(gdb) p/x *(TCR *)0x417e77d0

That address is the value of the "tcr" argument to "resume_tcr()" in
frame #7 in the backtrace below, so if you don't still have the
debugging session and reproduce the problem, we want to see what
the value of the "tcr" argument to resume_tcr() at the point was
at the point where resume_tcr() called sem_post() and crashed.

The gdb command above means "print, in hex, this contents of
what this address points to, interpreting that address as
being of type "pointer to TCR" (where a TCR is a "Thread Context
Record" that contains several interesting fields.)

'resume_tcr()' basically does 'sem_post(tcr->resume)', and a crash
would make sense if tcr->resume was NULL.  If it was, then one of
the threads that's doing sem_timedwait() on its 'resume' semaphore
would presumably be waiting on a NULL semahore, and that doesn't
make sense.

On Mon, 21 Jul 2008, Osei Poku wrote:

> Got it to crash again....
>
>> 
>> Where are you (where is address *0x00002ADAFE2CA325) and how did
>> you get there ('bt' in GDB) ?
>> 
>> 
> This time %rip = 0x00002ABAFDCCD325.  After I set the break point, continued 
> and typed X into the kernel debugger, I arrive here in gdb.  I will try not 
> to screw up the debugging session like last time so that I can provide 
> additional information.
>
> (gdb) bt
> #0  0x00002abafdccd325 in sem_post () from /lib64/libpthread.so.0
> #1  0x000000000041b3e2 in resume_tcr (tcr=0x40e577d0) at 
> ../thread_manager.c:1376
> #2  0x000000000041c0ba in resume_other_threads (for_gc=<value optimized out>) 
> at ../thread_manager.c:1544
> #3  0x000000000041d62e in lisp_Debugger (xp=0x4131dd60, info=0x4131e110, 
> why=11, in_foreign_code=1, message=0x4131db10 "Unhandled exception 11 at 
> 0x2abafdccd325, context->regs at #x4131dd88") at ../lisp-debug.c:919
> #4  0x000000000041a2c6 in signal_handler (signum=11, info=0x4131e110, 
> context=0x4131dd60, tcr=0x4131f7d0, old_valence=1) at 
> ../x86-exceptions.c:1070
> #5  <signal handler called>
> #6  0x00002abafdccd325 in sem_post () from /lib64/libpthread.so.0
> #7  0x000000000041b3e2 in resume_tcr (tcr=0x417e77d0) at 
> ../thread_manager.c:1376
> #8  0x000000000041c146 in lisp_resume_tcr (tcr=0x417e77d0) at 
> ../thread_manager.c:1418
> #9  0x000000000041a0c8 in handle_exception (signum=<value optimized out>, 
> info=0x4131eaa0, context=0x4131e6f0, tcr=0x4131f7d0, old_valence=0) at 
> ../x86-exceptions.c:910
> #10 0x000000000041a218 in signal_handler (signum=4, info=0x4131eaa0, 
> context=0x4131e6f0, tcr=0x4131f7d0, old_valence=0) at 
> ../x86-exceptions.c:1064
> #11 <signal handler called>
> #12 0x00003000400110ab in ?? ()
> #13 0x00003000404265fc in ?? ()
> #14 0x000000000040e0ac in _SPnthrowvalues () at ../x86-spentry64.s:1404
> #15 0x00002aaaad3e0110 in ?? ()
> #16 0x0000000000000008 in ?? ()
> #17 0x0000000000000000 in ?? ()
> (gdb) info threads
> 10 Thread 0x40263950 (LWP 6218)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 9 Thread 0x404c7950 (LWP 6219)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 8 Thread 0x4072b950 (LWP 6223)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 7 Thread 0x4098f950 (LWP 6224)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 6 Thread 0x40bf3950 (LWP 6225)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 5 Thread 0x410bb950 (LWP 8021)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> * 4 Thread 0x4131f950 (LWP 8307)  0x00002abafdccd325 in sem_post () from 
> /lib64/libpthread.so.0
> 3 Thread 0x40e57950 (LWP 8308)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 2 Thread 0x41583950 (LWP 8309)  0x00002abafdccd2cb in sem_timedwait () from 
> /lib64/libpthread.so.0
> 1 Thread 0x2abafe223880 (LWP 6215)  0x00002abafdccd2cb in sem_timedwait () 
> from /lib64/libpthread.so.0
> (gdb)
>