Hi Jaromir, Hi Nicolas,

On Sun, May 8, 2022 at 8:17 AM Jaromir Matas <mail at jaromir.net> wrote:

> Hi Nicolas,
>
>
>
> >> About the latest VM, (Smalltalk processSuspensionUnblocks) answers
> about the behavior of primitiveSuspend (#88).
>
> > Err,  wrong wording (Smalltalk processSuspensionUnblocks) does not
> describe the behavior of primitiveSuspend #(88).
>
> > It answers whether the VM has primitives #578 and #588 (see
> #getCogVMFeatureFlags in VMMaker)...
>
> >
>
> Yes, thanks, well that was the original idea for Smalltalk
> processSuspensionUnblocks  to answer about the behavior of the
> primitiveSuspend #88; which was before the primitives #568 and #578 were
> introduced. (And which was when I wrote the tests using this original
> logic). However that approach ran into problems with some existing
> implementations (e.g. Virtend) and as a result the two new primitives were
> introduced (#568 and #578) - and apparently the logic of what Smalltalk
> processSuspensionUnblocks answers about changed. Since then I haven't heard
> from Eliot about his plans how to proceed with the new suspend semantics or
> whether this is it :)
>

Apologies for not responding sooner.  It seems to me the semantics must
remain as they are, and it be left up to the image to bind suspend to the
primitive most convenient. Then backwards compatibility can be provided for
cases such as DelayWaitTimeout by providing a renamed suspend which
accesses the old primitive.  Sorry about not renaming
processSuspensionUnblocks.  This should be something like Smalltalk
hasExtendedProcessSuspensionSemantics or some such.



>
> In case this is still WIP I'd quite like an approach similar to Smalltalk
> processPreemptionYields - you'd set Smalltalk processSuspensionUnblocks
> true or false depending on how you want the VM to behave and the VM would
> use the right semantics (unless this is too naive :) ).
>
>
>
> Regarding the tests failing with the newest VM:
>
> testAtomicSuspend - we can remove this updated version and leave the
> existing one for the moment
>
> testRevisedSuspendExpectations - we can leave this one out too
>
> testTerminateBlockedInNestedEnsure1 - I'll take a look at these two and
> try to adjust the logic
>
> testTerminateBlockedInNestedEnsure2
>
>
>
> All remaining test in KernelTests-jar.421 work as intended.
>
>
>
> Thanks again,
>
> Jaromir
>
>
>
> --
>
> *Jaromír Matas*
>
> mail at jaromir.net
>
>
>
> *From: *Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>
> *Sent: *Sunday, May 8, 2022 16:22
> *To: *The general-purpose Squeak developers list
> <squeak-dev at lists.squeakfoundation.org>
> *Subject: *Re: [squeak-dev] SIGTRAP when Proceeding from BlockCannotReturn
>
>
>
>
>
>
>
> Le dim. 8 mai 2022 à 15:59, Nicolas Cellier <
> nicolas.cellier.aka.nice at gmail.com> a écrit :
>
>
>
>
>
> Le dim. 8 mai 2022 à 14:16, Nicolas Cellier <
> nicolas.cellier.aka.nice at gmail.com> a écrit :
>
> Hi Jaromir
>
>
>
> Le sam. 7 mai 2022 à 14:45, Jaromir Matas <mail at jaromir.net> a écrit :
>
> Hi Marcel, Nicolas, Eliot,
>
>
>
>
>
> > (Nicolas) I have merged Kernel-jar.1446 which is trivial (re-signal an
> Exception).
>
>
>
> Thanks!
>
>
>
> > (Marcel) Hmm... #testSimpleResignalVsOuter1 is still failing.
>
>
>
> In my latest trunk image it passes ok (5/7/22)
>
>
>
> >> (Marcel) I will also take a look at KernelTests-jar.421 to check
> whether any new semantics are okay.
>
> >>
>
> > (Nicolas) Yes, I did that and got two failing tests
>
> > testTerminateTerminatingProcess
>
> > testResumeTerminatingProcess
>
> >
>
> > both failures look the same, in second self assert: terminator
> isSuspended.
>
>
>
> Yes, they are supposed to fail at the moment so I suggest to make them
> expected failures/feature requests. However there's a stupid bug in both
> I’ve fixed now: they were indeed supposed to fail the following assertion:
>
> ``` self should: [terminatee terminate] raise: Error. ```
>
>
>
> Apologies for the confusion - an updated changeset is enclosed.
>
>
>
>
>
> However, there's another issue regarding the revised #suspend semantics
> Eliot has been working on. I've updated the process tests in
> KernelTests-jar.421 to test both the old and the new #suspend semantics.
> The two semantics should be distinguishable via Smalltalk
> processSuspensionUnblocks flag answering true in case of the old semantics
> and false in case of the revised one; my updated tests use this logic.
> However, unfortunately the latest VM answers "false" but uses the OLD
> suspend semantics in #suspend prim 88.
>
>
>
> So I'm surprised you haven't observed more tests failing due to the new
> suspend semantics... What VM have you used – an older one? I'm on the
> latest trunk's VM 3183. And what is the answer of Smalltalk
> processSuspensionUnblocks? :) I'm utterly confused...
>
>
>
> Hi Eliot - I may be confused here but if the current VM uses the old
> #suspend prim 88 semantics, shouldn't ```Smalltalk
> processSuspensionUnblocks``` answer true?
>
>
>
>
>
> Indeed, I can confirm that the latest VM does answer false to (Smalltalk
> processSuspensionUnblocks).
>
> Though, process suspension still unblocks as shown by the example at
>
> https://github.com/pharo-project/pharo/issues/10669
>
>
>
> A bit more simply, this answers false - it shouldn't:
>
>
>
> s := Semaphore new.
> p := [s wait] newProcess.
> p resume.
> 100 milliSeconds wait.
> p suspend; resume.
> 100 milliSeconds wait.
> p isTerminated = Smalltalk processSuspensionUnblocks.
>
>
>
> technically, this answers false - it shouldn't:
>
>
>
> s := Semaphore new.
> p := [s wait] newProcess.
> p resume.
> 100 milliSeconds wait.
> p suspend == s = Smalltalk processSuspensionUnblocks
>
>
>
>
>
> About the latest VM, (Smalltalk processSuspensionUnblocks) answers about
> the behavior of primitiveSuspend (#88).
>
> Err,  wrong wording (Smalltalk processSuspensionUnblocks) does not
> describe the behavior of primitiveSuspend #(88).
>
> It answers whether the VM has primitives #578 and #588 (see
> #getCogVMFeatureFlags in VMMaker)...
>
>
>
> The new Behavior is implemented by primitiveSuspendBackingUpV1 (#578) and
> primitiveSuspendBackingUpV2 (#588).
>
> V1 always answers the old list (even if a Semaphore/Mutex), V2 answers nil
> in case of Semaphore/Mutex.
>
>
>
> So, only ((Process>>#suspend) primitive) can give you a clue about the
> behavior, assuming that the primitive in question is implemented...
>
>
>
> So it depends if we want to make it a Preference, or make the image
> compatible with some less capable VM...
>
>
>
> we could implement
>     Process>>primitiveSuspendAndUnblock as <primitive: 88>
>     Process>>primitiveSuspend as <primitive: 588>
>
> test the VM flag in suspend
>
>     Process>>suspend
>
>         ^(VMHasPrimitiveSuspendBackingUp ifNil:
> [VMHasPrimitiveSuspendBackingUp := Smalltalk processSuspensionUnblocks not])
>
>             ifTrue: [self primitiveSuspend]
>
>             ifFalse: [self primitiveSuspendAndUnblock]
>
> Then arrange to reset VMHasPrimitiveSuspendBackingUp to nil at snapshot...
>
>
>
> I will tell next week about the status of the VM which I used for testing,
> it's possibly a few months old.
>
>
>
> > (Nicolas) I would also consider 1445 1421 and most importantly 1447.
>
>
>
> Regarding 1421: alternatively, you might consider a newer version 1415
> where the only difference is #return:from: passes a block instead of nil to
> #resume:through: to cause a fresh search for the first unwind context;
> otherwise they are equivalent.
>
>
>
> OK, I will check again.
>
>
>
> > (Marcel) Maybe we can just merge
>
> >
>
> > KernelTests-jar.393
>
> > KernelTests-jar.418
>
> > KernelTests-jar.421
>
> >
>
> > And go from there? Or are there any objections?
>
>
>
> KernelTests-jar.393 is just a special case of a more general
> KernelTests-jar.418 test…
>
>
>
> In my image all tests are green provided Smalltalk
> processSuspensionUnblocks answers true and the two above tests Nicolas
> mentioned are marked expected failures :)
>
>
>
> Thanks very much for your feedback,
>
> Jaromir
>
>
>
> --
>
> Jaromír Matas
>
> mail at jaromir.net
>
>
>
>
>
>

-- 
_,,,^..^,,,_
best, Eliot
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