[squeak-dev] Difficult to debug VM crash with full blocks and Sista V1

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Mon Sep 16 21:05:37 UTC 2019


Forgot to say: it happens in spur only, not stack.

Le lun. 16 sept. 2019 à 22:52, Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com> a écrit :

> No idea if this is related or not,
> but i got regular crash on macos own compiled x64 artefact by just running:
>     SocketTest suite run.
>
> I first though about inquiring some UB, but this happens in debug version,
> so it's probably something else.
> I did not try to simulate (but can we simulate socket tests?).
> This does not happen in windows 64 nor linux 64 (wsl) where I can run all
> the tests.
> Note that on wsl i had to evaluate (Compiler recompileAll) in
> trunk6-64.image, otherwise a bunch of tests are failing... Mysterious.
> I also had 2 ByteSymbol differing from their interned version.
>
> Le sam. 14 sept. 2019 à 09:33, Tobias Pape <Das.Linux at gmx.de> a écrit :
>
>>
>> > On 14.09.2019, at 06:03, Nicola Mingotti <nmingotti at gmail.com> wrote:
>> >
>> >
>> > I can help you a bit only on this point:
>> > "- is there a way of introducing network delays in Mac OS that might
>> help me induce the bug?"
>>
>> Yea it is called "network link conditioner.prefpane" :D
>>
>>
>> >
>> > Yes, in theory it is possible. Some time ago I red the documentation of
>> 'dummynet' in FreeBSD for the firewall 'ipfw', it seemed to be very
>> interesting but I never had occasion to use it.
>> >
>> > Now, Apple Unix is in large part taken from FreeBSD => I check if they
>> took also dummynet:
>> > macOS> apropos dummynet
>> > dummynet(4) ....
>> >
>> > So, yes, it is there.
>> >
>> > HTH
>> >
>> > bye
>> > Nicola
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > On 9/13/19 8:15 PM, Eliot Miranda wrote:
>> >> Hi All,
>> >>
>> >>     there is a VM bug in 64-bit Spur with the Sista V1 bytecode set
>> and full blocks.  The symptom is that when waiting for a remote Monticello
>> repository to update and/or deliver a package version the system crashes in
>> JITTED code after what appears to be some kind of wait.
>> >>
>> >> This is a reliably occurring bug b ut maddeningly difficult to
>> reproduce.  The bug reliably occurs when interacting with a remote
>> rep[ository (e.g. http://source.squeak.org/VMMaker) when the server is
>> "cold", and hence makes the image wait.  Every time I have tried to repeat
>> the failing sequence the crash has not occurre3d, I think because the
>> server is now "hot" and serves up the version quickly.  Today I even tried
>> shutting down my machine for over an hour and rebooting.  But I could not
>> get the crash to occur even though it seems to me that every time I try it
>> the first time in the4 day it does crash.
>> >>
>> >> This is an important bug to fix.  If it cannot be fixed then full
>> blocks and Sista V1 are not ready for use in the upcoming Squeak release.
>> I am looking for help in debugging this.
>> >>
>> >> - is anyone else uising the 64-bit VM with full blocks and Sista V1
>> who sees hard VM crashes?  If so, under what circumstances?
>> >>
>> >> - is it possible to flush caches in the
>> http://source.squeak.org/VMMaker server, or could people tolerate me
>> rebooting the server?
>> >>
>> >> - is there a way of introducing network delays in Mac OS that might
>> help me induce the bug?
>> >>
>> >> - can anyone think of any other strategies I might take to try and
>> reproduce this?
>> >>
>> >> I may have to try and reproduce e the bug in the simulator to have a
>> chance of identifying the bug.  Does anyone have a good enough mental model
>> of the Monticello server interaction and have energy to help me figure this
>> one out?
>> >>
>> >> Here is some information from the last crash I did see in the debugger
>> (alas it is incomplete; there are a number of additional pieces of info I
>> could have collected).
>> >>
>> >> (lldb) thr b
>> >> * thread #1, queue = 'com.apple.main-thread', stop reason =
>> EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
>> >>   * frame #0: 0x000000010de5700a
>> >>     frame #1: 0x000000010dd7b174
>> >>     frame #2: 0x000000010dd45f1c
>> >>     frame #3: 0x000000010dd44534
>> >>     frame #4: 0x000000010dd44c60
>> >> (lldb) x/10i 0x000000010de5700a
>> >>
>> >> (lldb) call printStackCallStackOf($rbp)
>> >>     0x7ffeefbdfc30 M Heap>upHeap: 0x11273ca90: a(n) Heap
>> >>     0x7ffeefbdfc68 M Heap>add: 0x11273ca90: a(n) Heap
>> >>     0x7ffeefbdfca0 M Delay class>scheduleDelay:from: 0x1123ebfb8: a(n)
>> Delay class
>> >>     0x7ffeefbdfcf0 M Delay class>handleTimerEvent 0x1123ebfb8: a(n)
>> Delay class
>> >>     0x7ffeefbdfd20 M Delay class>runTimerEventLoop 0x1123ebfb8: a(n)
>> Delay class
>> >>
>> >> (lldb) x/10i 0x000000010dd7b174
>> >>     0x10dd7b174: 48 8b 55 10  movq   0x10(%rbp), %rdx
>> >>     0x10dd7b178: 48 89 ec     movq   %rbp, %rsp
>> >>     0x10dd7b17b: 5d           popq   %rbp
>> >>     0x10dd7b17c: c2 10 00     retq   $0x10
>> >>     0x10dd7b17f: cc           int3
>> >>     0x10dd7b180: cc           int3
>> >>     0x10dd7b181: cc           int3
>> >>     0x10dd7b182: cc           int3
>> >>     0x10dd7b183: cc           int3
>> >>     0x10dd7b184: cc           int3
>> >> (lldb) print whereIs(0x000000010dd7b174)
>> >> (char *) $0 = 0x00000001000f83ff " is in generated methods"
>> >> (lldb) call printCogMethodFor((void *)0x000000010dd7b174)
>> >>        0x10dd7afc0 <->        0x10dd7b198: method:        0x112f23c10
>> selector:        0x112232c20 add:
>> >> (lldb) print whereIs(0x000000010de5700a)
>> >> (char *) $1 = 0x00000001000f83ff " is in generated methods"
>> >> (lldb) call printCogMethodFor((void *)0x000000010de5700a)
>> >>        0x10de56ba0 <->        0x10de57078: method:        0x1126ec218
>> prim 23856 selector:     0x7ffeefbf3d20
>> >>
>> >> this method ends up being the fitted version of Delay class>>
>> startTimerEventLoop
>> >> _,,,^..^,,,_
>> >> best, Eliot
>> >>
>> >>
>> >
>> >
>>
>>
>>
>>
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