Re: Core dump when throwing an exception from a resumed partial continuation

[Andrew Gaylard]

On 03/15/13 23:30, Andy Wingo wrote:

On Fri 15 Mar 2013 22:01, Brent Pinkney <address@hidden> writes:

I am using partial continuations to resume a computation when an
external system returns with an answer.
I am using (call-with-prompt ...) and (abort-to-prompt)

When I resume the continuation in another thread, all works perfectly

Neat :)

UNLESS the continued execution throws and exception.
Then guile exits with a core dump.

That's not good!  Can you work up a short test case?

We've tried to create a short test-case.  Unfortunately, it doesn't seem to trigger the core.  However, the app we're creating triggers the core-dump every time. So, to dig into this problem, I built a debuggable VM.

What we see in the debuggable cores is the first backtrace.  You'll note that aside from the stack overflow at frame #3, the pattern of "Abort to unknown prompt" is repeated ad infinitum.  Well, certainly to a stack depth of 28,000 :).  So the stack overflow is understandable.  I guess the question is,  why does guile get stuck in a loop aborting to an unknown prompt?.

This is on Linux x86 Ubuntu 12.04, both 32- and 64-bit.  The same code crashes the same VM at the same point on Solaris SPARC 64-bit, but that core does not appear to show this repetitive pattern.  When I say the "same VM", I mean it: all dependencies except for the kernel and libc are built from identical sources, using as near as possible the same configure flags:

gcc-4.7.2
bdw-gc-7.2d
libtool-2.2.10
gmp-5.0.2
libiconv-1.14
libunistring-0.9.3
libffi-3.0.10
readline-6.1
guile-2.0.7

Ubuntu's guile also shows the same problem.

To understand how guile gets into this state, I put a breakpoint in the VM at the point where it first calls abort. That reveals the second backtrace below.  This shows what happens immediately before the VM goes bananas, and fills up the stack.  Which is exactly what happens when gdb allows guile to continue beyond the breakpoint.

I then tried stepping through the scm_c_abort code in frame #2, and it indeed does not find anything in the wind list.  Certainly, the list returned by scm_i_dynwinds has 12 entries in it.  It's just that none of them match.

I'd be really grateful for any help on this -- as you can tell, I'm not a VM hacker!

--
Andrew

#0  0x0033b416 in __kernel_vsyscall ()
#1  0x004ff1df in __GI_raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#2  0x00502825 in __GI_abort () at abort.c:91
#3  0x00a106b7 in vm_error_stack_overflow (vp=0x9c9cfc0) at vm.c:516
#4  0x00a204a4 in vm_regular_engine (vm=0x9cb29e8, program=0x93b50d0, argv=0xac055e70, nargs=4) at vm-engine.c:166
#5  0x00a34d00 in scm_c_vm_run (vm=0x9cb29e8, program=0x93b50d0, argv=0xac055e70, nargs=4) at vm.c:741
#6  0x00a3585e in scm_call_with_vm (vm=0x9cb29e8, proc=0x93b50d0, args=0x304) at vm.c:1033
#7  0x009763e1 in scm_apply (proc=0x93b50d0, arg1=0x95dd4c8, args=0x95dd4c8) at eval.c:748
#8  0x00975f7c in scm_apply_1 (proc=0x93b50d0, arg1=0x937df10, args=0x95dd4d0) at eval.c:588
#9  0x00a0ba1d in scm_throw (key=0x937df10, args=0x95dd4d0) at throw.c:104
#10 0x00a102ff in vm_error (msg=0xa6631d "VM: Too many arguments", arg=0x16) at vm.c:414
#11 0x00a105e6 in vm_error_too_many_args (nargs=5) at vm.c:490
#12 0x00a11a42 in vm_regular_engine (vm=0x9cb29e8, program=0x93b50d0, argv=0xac056770, nargs=5) at vm-engine.c:104
#13 0x00a34d00 in scm_c_vm_run (vm=0x9cb29e8, program=0x93b50d0, argv=0xac056770, nargs=5) at vm.c:741
#14 0x00a3585e in scm_call_with_vm (vm=0x9cb29e8, proc=0x93b50d0, args=0x304) at vm.c:1033
#15 0x009763e1 in scm_apply (proc=0x93b50d0, arg1=0x95dd550, args=0x95dd550) at eval.c:748
#16 0x00975f7c in scm_apply_1 (proc=0x93b50d0, arg1=0x9362130, args=0x95dd558) at eval.c:588
#17 0x00a0ba1d in scm_throw (key=0x9362130, args=0x95dd558) at throw.c:104
#18 0x00a0c097 in scm_ithrow (key=0x9362130, args=0x95dd558, noreturn=1) at throw.c:441
#19 0x009735bf in scm_error_scm (key=0x9362130, subr=0x99105b0, message=0x99105c0, args=0x95dd5c8, data="" at error.c:95
#20 0x00973576 in scm_error (key=0x9362130, subr=0xa4cd3b "abort", message=0xa4cd23 "Abort to unknown prompt", args=0x95dd5c8, rest=0x4) at error.c:62
#21 0x00973b6b in scm_misc_error (subr=0xa4cd3b "abort", message=0xa4cd23 "Abort to unknown prompt", args=0x95dd5c8) at error.c:316
#22 0x0096aef5 in scm_c_abort (vm=0x9cb29e8, tag=0x9c08af0, n=5, argv=0xac056960, cookie=6614) at control.c:209
#23 0x00a0fe36 in vm_abort (vm=0x9cb29e8, n=0, vm_cookie=6614) at vm.c:264
#24 0x00a18942 in vm_regular_engine (vm=0x9cb29e8, program=0x93b5260, argv=0xac0571f4, nargs=6) at vm-i-system.c:1528
#25 0x00a34d00 in scm_c_vm_run (vm=0x9cb29e8, program=0x93b50d0, argv=0xac0571e0, nargs=5) at vm.c:741
#26 0x00a3585e in scm_call_with_vm (vm=0x9cb29e8, proc=0x93b50d0, args=0x304) at vm.c:1033
#27 0x009763e1 in scm_apply (proc=0x93b50d0, arg1=0x95dd678, args=0x95dd678) at eval.c:748
#28 0x00975f7c in scm_apply_1 (proc=0x93b50d0, arg1=0x9362130, args=0x95dd680) at eval.c:588
#29 0x00a0ba1d in scm_throw (key=0x9362130, args=0x95dd680) at throw.c:104
#30 0x00a0c097 in scm_ithrow (key=0x9362130, args=0x95dd680, noreturn=1) at throw.c:441
#31 0x009735bf in scm_error_scm (key=0x9362130, subr=0x99105d0, message=0x99105e0, args=0x95dd6a0, data="" at error.c:95
#32 0x00973576 in scm_error (key=0x9362130, subr=0xa4cd3b "abort", message=0xa4cd23 "Abort to unknown prompt", args=0x95dd6a0, rest=0x4) at error.c:62
#33 0x00973b6b in scm_misc_error (subr=0xa4cd3b "abort", message=0xa4cd23 "Abort to unknown prompt", args=0x95dd6a0) at error.c:316
#34 0x0096aef5 in scm_c_abort (vm=0x9cb29e8, tag=0x9c08af0, n=5, argv=0xac0573d0, cookie=6613) at control.c:209
#35 0x00a0fe36 in vm_abort (vm=0x9cb29e8, n=0, vm_cookie=6613) at vm.c:264
#36 0x00a18942 in vm_regular_engine (vm=0x9cb29e8, program=0x93b5260, argv=0xac057c64, nargs=6) at vm-i-system.c:1528
#37 0x00a34d00 in scm_c_vm_run (vm=0x9cb29e8, program=0x93b50d0, argv=0xac057c50, nargs=5) at vm.c:741
#38 0x00a3585e in scm_call_with_vm (vm=0x9cb29e8, proc=0x93b50d0, args=0x304) at vm.c:1033
#39 0x009763e1 in scm_apply (proc=0x93b50d0, arg1=0x95dd730, args=0x95dd730) at eval.c:748
#40 0x00975f7c in scm_apply_1 (proc=0x93b50d0, arg1=0x9362130, args=0x95dd738) at eval.c:588
#41 0x00a0ba1d in scm_throw (key=0x9362130, args=0x95dd738) at throw.c:104
#42 0x00a0c097 in scm_ithrow (key=0x9362130, args=0x95dd738, noreturn=1) at throw.c:441
#43 0x009735bf in scm_error_scm (key=0x9362130, subr=0x99105f0, message=0x9910600, args=0x95dd758, data="" at error.c:95
#44 0x00973576 in scm_error (key=0x9362130, subr=0xa4cd3b "abort", message=0xa4cd23 "Abort to unknown prompt", args=0x95dd758, rest=0x4) at error.c:62
#45 0x00973b6b in scm_misc_error (subr=0xa4cd3b "abort", message=0xa4cd23 "Abort to unknown prompt", args=0x95dd758) at error.c:316
#46 0x0096aef5 in scm_c_abort (vm=0x9cb29e8, tag=0x9c08af0, n=5, argv=0xac057e40, cookie=6612) at control.c:209
#47 0x00a0fe36 in vm_abort (vm=0x9cb29e8, n=0, vm_cookie=6612) at vm.c:264


#0  scm_error (key=0x80a7130, subr=0x25cd5b "abort", message=0x25cd43 "Abort to unknown prompt", args=0x857cf50, rest=0x4) at error.c:62
#1  0x00183b6b in scm_misc_error (subr=0x25cd5b "abort", message=0x25cd43 "Abort to unknown prompt", args=0x857cf50) at error.c:316
#2  0x0017aef5 in scm_c_abort (vm=0x8531ca8, tag=0x8800a20, n=1, argv=0xa99f8f30, cookie=1) at control.c:209
#3  0x0021fe4a in vm_abort (vm=0x8531ca8, n=0, vm_cookie=1) at vm.c:264
#4  0x00228956 in vm_regular_engine (vm=0x8531ca8, program=0x815a750, argv=0xa99f97b0, nargs=2) at vm-i-system.c:1528
#5  0x00244d14 in scm_c_vm_run (vm=0x8531ca8, program=0x80c95a0, argv=0xa99f97a4, nargs=3) at vm.c:741
#6  0x00185baa in scm_call_3 (proc=0x80c95a0, arg1=0x404, arg2=0x850b240, arg3=0x84255e8) at eval.c:500
#7  0x0021b866 in scm_catch (key=0x404, thunk=0x850b240, handler=0x84255e8) at throw.c:73
#8  0x00218dad in really_launch (d=0xb19fcf34) at threads.c:1007
#9  0x0017ba40 in c_body (d=0xa99fa194) at continuations.c:511
#10 0x0021bb28 in apply_catch_closure (clo=0x892ac50, args=0x304) at throw.c:146
#11 0x001f03cb in apply_1 (smob=0x892ac50, a=0x304) at smob.c:141
#12 0x002253e2 in vm_regular_engine (vm=0x8531ca8, program=0x80f94b0, argv=0xa99fa0b0, nargs=2) at vm-i-system.c:853
#13 0x00244d14 in scm_c_vm_run (vm=0x8531ca8, program=0x80c95a0, argv=0xa99fa0a0, nargs=4) at vm.c:741
#14 0x00185bfd in scm_call_4 (proc=0x80c95a0, arg1=0x404, arg2=0x892ac50, arg3=0x892ac30, arg4=0x892ac20) at eval.c:507
#15 0x0021b91e in scm_catch_with_pre_unwind_handler (key=0x404, thunk=0x892ac50, handler=0x892ac30, pre_unwind_handler=0x892ac20) at throw.c:86
#16 0x0021bbee in scm_c_catch (tag=0x404, body=0x17ba24 <c_body>, body_data=0xa99fa194, handler=0x17ba4d <c_handler>, handler_data=0xa99fa194, pre_unwind_handler=0x17baa0 <pre_unwind_handler>, pre_unwind_handler_data=0x80fdf80) at throw.c:213
#17 0x0017b8ab in scm_i_with_continuation_barrier (body=0x17ba24 <c_body>, body_data=0xa99fa194, handler=0x17ba4d <c_handler>, handler_data=0xa99fa194, pre_unwind_handler=0x17baa0 <pre_unwind_handler>, pre_unwind_handler_data=0x80fdf80) at continuations.c:449
#18 0x0017bb40 in scm_c_with_continuation_barrier (func=0x218d07 <really_launch>, data="" at continuations.c:545
#19 0x00218b85 in with_guile_and_parent (base=0xa99fa1f8, data="" at threads.c:906
#20 0x002e248c in GC_call_with_stack_base () from /opt/cs/components/3rd/bdw-gc/7.2.7e16553s16377h0398/lib/libgc.so.1
#21 0x00218c48 in scm_i_with_guile_and_parent (func=0x218d07 <really_launch>, data="" parent=0x881e5d8) at threads.c:949
#22 0x00218e01 in launch_thread (d=0xb19fcf34) at threads.c:1017
#23 0x002e79b7 in GC_inner_start_routine () from /opt/cs/components/3rd/bdw-gc/7.2.7e16553s16377h0398/lib/libgc.so.1
#24 0x002e248c in GC_call_with_stack_base () from /opt/cs/components/3rd/bdw-gc/7.2.7e16553s16377h0398/lib/libgc.so.1
#25 0x002e8d69 in GC_start_routine () from /opt/cs/components/3rd/bdw-gc/7.2.7e16553s16377h0398/lib/libgc.so.1
#26 0x00321d4c in start_thread (arg=0xa99fab40) at pthread_create.c:308
#27 0x00722d3e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130