[Vm-dev] Re: primitive retry across suspension for OwnedLock waitAcquire (was: Interpreter versus StackInterpreter hierarchy)

[Ben Coman]

On Fri, Jun 3, 2016 at 6:33 PM, Ben Coman <btc at openinworld.com> wrote:

> where  OwnedLock>>experiment1   is...
>     | result |
>     result := OrderedCollection new: 20.
>     result myAdd: 0.

btw, OrderedCollection>>myAdd:
is direct copy of OrderderedCollection>>add:
just so [set break selector...] can distinguish these from every send
of add: in the image.


> The current VM produces a result of...
>      OrderedCollection(0 11 12 21 22 13 14 24 8 9)
>
> but I'm hoping to get something like...
>      OrderedCollection(0 11 12 21 22 14 23 24 8 9)


After loading my 'ownedlock-reader.image' with an unchaged VM,
then adding these two lines to transferTo:

>     objectMemory
>         storeInteger: SuspendedPrimitiveFailCodeIndex
>         ofObject: oldProc
>         withValue: primFailCode.
>     primFailCode := objectMemory
>        fetchInteger: SuspendedPrimitiveFailCodeIndex
>        ofObject: newProc.

then executing...    OwnedLock new experiment1 !
I get an AssertionFailure in...

Spur32BitMMLESimulator>>fetchPointer: fieldIndex ofObject: objOop
    self assert: (self isForwarded: objOop) not.
    self assert: (fieldIndex >= 0 and: [fieldIndex < (self
numSlotsOfAny: objOop)
           or: [fieldIndex = 0 "forwarders and free objs"]]).
    ^super fetchPointer: fieldIndex ofObject: objOop

where...
  objOop  ==>
      16r2D2490: a(n) OwnedLock
           16r41A280 nil   16r41A280 nil   16r41A280 nil

  fieldIndex  ==>  3

  self numSlotsOfAny: objOop  ==>  3


One thing I'm curious about is why the " < " and not a " <= " ?
    super fetchPointer: fieldIndex ofObject: objOop
successfully returns...   16r41A280: a(n) UndefinedObject


btw, here is the call stack...
   -16r106C [] in OwnedLock>experiment1 16r2D2490: a(n) OwnedLock
   -16r104C BlockClosure>on:do: 16r2D29C8: a(n) BlockClosure
   -16r1024 [] in OwnedLock>experiment1 16r2D2490: a(n) OwnedLock
   -16r1008 [] in BlockClosure>newProcess 16r2D27E8: a(n) BlockClosure

and the ext head frame...
   -16r106C [] in OwnedLock>experiment1 16r2D2490: a(n) OwnedLock
   -16r1064/3559:   rcvr/clsr:   16r2D29C8 a BlockClosure
   -16r1068/3558:cllr ip/ctxt:   16rA3F922=10746146
   -16r106C/3557:    saved fp:    -16r104C=-4172
   -16r1070/3556:      method:   16r81EF10 a CompiledMethod
   -16r1074/3555:       flags:  16r1010001=16842753  numArgs: 0
hasContext: true  isBlock: true
   -16r1078/3554:     context:   16r2D29F8=2959864
   -16r107C/3553:    receiver:   16r2D2490 an OwnedLock
   -16r1080/3552:   temp/stck:   16r2D24A8 an OrderedCollection
   -16r1084/3551:   temp/stck:   16r2D2490 an OwnedLock

and the int head frame...
   -16r108C OwnedLock(Process)>suspend 16r2D2490: a(n) OwnedLock
   -16r1084/3551:   rcvr/clsr:   16r2D2490 an OwnedLock
   -16r1088/3550:cllr ip/ctxt:   16r81EFBB=8515515
   -16r108C/3549:    saved fp:    -16r106C=-4204
   -16r1090/3548:      method:  16r10DF5B0 a CompiledMethod
   -16r1094/3547:       flags:        16r1=1  numArgs: 0  hasContext:
false  isBlock: false
   -16r1098/3546:     context:   16r41A280=4301440
   -16r109C/3545:    receiver:   16r2D2490 an OwnedLock
   -16r10A0/3544:   temp/stck:   16r41A280 nil


What is the difference between ext and int  head frames?

One thing I find curious here is "OwnedLock(Process)>suspend".  Does
this indicate that #suspend was sent to an OwnedLock and looked up the
hierarchy to find the method in Process?
But OwnedLock doesn't inherit from Process, it inherits from LinkedList.

cheers -ben