[squeak-dev] The Trunk: Kernel-eem.1484.mczJaromir Matas mail at jaromir.netMon Jun 27 08:12:25 UTC 2022
Hi Marcel, I think we have oversimplified #signalException. It looks like only tests use it in the Trunk (and those test are ok either way) but Eliot apparently has some not-so-happy usages elsewhere. My suggestion is attached; unfortunately there are no tests for this functionality so I guess the ultimate criteria is whether it works for Eliot ;) Best, Jaromir -- Jaromír Matas mail at jaromir.net From: Marcel Taeumel<mailto:marcel.taeumel at hpi.de> Sent: Monday, June 27, 2022 9:38 To: squeak-dev<mailto:squeak-dev at lists.squeakfoundation.org> Subject: Re: [squeak-dev] The Trunk: Kernel-eem.1484.mcz Hi Eliot, hi Jaromir -- Please resolve this issue ASAP. I did not expect such a commit given that we are in "CODE FREEZE" at this point. A short notice/discussion would have been nice. Yet, thanks for working on this issue. :-) Can we leave it as is or is another change required? Best, Marcel Am 26.06.2022 23:57:23 schrieb Jaromir Matas <mail at jaromir.net>: Hi Eliot, How about like this: signalException: anException "Signal an exception in the receiver process...if the receiver is currently suspended, the exception will get signaled when the receiver is resumed. If the receiver is blocked on a Semaphore, it will be immediately re-awakened and the exception will be signaled; if the exception is resumed, then the receiver will return to a blocked state unless the blocking Semaphore has excess signals" | oldList | "If we are the active process, go ahead and signal the exception" self isActiveProcess ifTrue: [^anException signal]. "Suspend myself first to ensure that I won't run away in the midst of the following modifications." (oldList := myList) ifNotNil: [self suspend]. suspendedContext ifNil: [self error: 'no suspended context!!']. "Add a new method context to the stack that will signal the exception" suspendedContext := Context sender: suspendedContext receiver: self method: (self class lookupSelector: #pvtSignal:) arguments: {anException}. "If we are not on a list to be run (i.e. this process is suspended), then when the process is resumed, it will signal the exception" oldList ifNotNil: [self resume] pvtSignal: anException "Private. This method is used to signal an exception from another process...the receiver must be the active process." "Since this method is not called in a normal way, we need to take care that it doesn't directly return to the caller (because I believe that could have the potential to push an unwanted object on the caller's stack)." | blocker | self isActiveProcess ifFalse: [^self]. anException signal. blocker := Semaphore new. [self suspend. suspendedContext := suspendedContext swapSender: nil. self resume] fork. blocker wait. -- Jaromír Matas mail at jaromir.net From: Jaromir Matas<mailto:mail at jaromir.net> Sent: Sunday, June 26, 2022 20:41 To: The general-purpose Squeak developers list<mailto:squeak-dev at lists.squeakfoundation.org> Subject: Re: [squeak-dev] The Trunk: Kernel-eem.1484.mcz Hi Eliot, I think the MNU error situation corresponds to the scenario described in pvtSignal:list:; unless I’m mistaken or you find more elegant way I’d suggest to use the helper method again; fortunately nicely simplified thanks to the new suspend: pvtSignal: anException "Private. This method is used to signal an exception from another process...the receiver must be the active process." "Since this method is not called in a normal way, we need to take care that it doesn't directly return to the caller (because I believe that could have the potential to push an unwanted object on the caller's stack)." | blocker | self isActiveProcess ifFalse: [^self]. anException signal. blocker := Semaphore new. [self suspend. suspendedContext := suspendedContext swapSender: nil. self resume] fork. blocker wait. What do you think? Best, Jaromir From: Jaromir Matas<mailto:mail at jaromir.net> Sent: Sunday, June 26, 2022 19:03 To: The general-purpose Squeak developers list<mailto:squeak-dev at lists.squeakfoundation.org> Subject: Re: [squeak-dev] The Trunk: Kernel-eem.1484.mcz Hi Eliot, Thanks for the examples; I have a problem with this one: p := [Semaphore new wait] fork. Processor yield. p signalException: Notification It gives me MNU: UndefinedObject>>wait The reason is: 1) you place the new context (Notification signal) on top of the previous suspendedContext (Semaphore new wait); its pc is at the wait. 2) now when the (Notification signal) context finally returns it places its return value on the top of its senders stack -> and this is a problem because when you send the wait it takes the stack top as the receiver (but that’s changed in the meantime) if I understand it correctly – resulting in the MNU Is this a bug? I’ve never used #signalException so I’m not entirely sure what to expect from it but it behaves differently than in 5.3. Enclosing a screen snip. If, at that moment, you do suspendedContext pop, the computation will proceed as expected. I’ll keep looking at it but wanted to let you know… Thanks, Jaromir -- Jaromír Matas mail at jaromir.net From: Eliot Miranda<mailto:eliot.miranda at gmail.com> Sent: Saturday, June 25, 2022 21:12 To: The general-purpose Squeak developers list<mailto:squeak-dev at lists.squeakfoundation.org> Subject: Re: [squeak-dev] The Trunk: Kernel-eem.1484.mcz On Sat, Jun 25, 2022 at 1:50 AM Jaromir Matas <mail at jaromir.net<mailto:mail at jaromir.net>> wrote: Hi Eliot, I missed that one, sorry. I’ve just tried this example and only got an assertion error (without your fix): p := [] newProcess suspendedContext: nil. p signalException: Error I just can’t figure out in which case you got the BCR exception :) In the VMMaker VM simulator, when the simulator window is closed, the closing code attempts to close any and all notifiers & debuggers . I'm working on the threaded FFI plugin, which in the simulator has multiple Smalltalk processes emulating OS threads. To close each notifier it needs to deliver a tagged Notification signal to the relevant process. Some of these processes are waiting on semaphores. If they are the old code would suspend, which would set the process's suspendedContext to nil, and result in a cannot return error as the signal was being delivered. So the example to test is p := [Semaphore new wait] fork. Processor yield. p signalException: Notification With the old signalException: version and the new suspend primitive this would crash with the BCR error. Or something like that. Maybe it had to be terminated, as in p := [Semaphore new wait] fork. Processor yield. p terminate. p signalException: Notification But you get the idea. If the process's suspendedContext is nil then the context that is put on top of the stack towards the end of signalException: will not be able to return. Thanks! Jaromir From: commits at source.squeak.org<mailto:commits at source.squeak.org> Sent: Saturday, June 25, 2022 1:58 To: squeak-dev at lists.squeakfoundation.org<mailto:squeak-dev at lists.squeakfoundation.org>; packages at lists.squeakfoundation.org<mailto:packages at lists.squeakfoundation.org> Subject: [squeak-dev] The Trunk: Kernel-eem.1484.mcz Eliot Miranda uploaded a new version of Kernel to project The Trunk: http://source.squeak.org/trunk/Kernel-eem.1484.mcz ==================== Summary ==================== Name: Kernel-eem.1484 Author: eem Time: 24 June 2022, 4:58:09.258613 pm UUID: f8ca934f-5875-434a-8cec-4d055099bdb6 Ancestors: Kernel-mt.1483 Fix a bug in Process>>signalException: where signalling a suspended process would cause a cannot return exception. =============== Diff against Kernel-mt.1483 =============== Item was changed: ----- Method: Process>>signalException: (in category 'signaling') ----- signalException: anException "Signal an exception in the receiver process...if the receiver is currently suspended, the exception will get signaled when the receiver is resumed. If the receiver is blocked on a Semaphore, it will be immediately re-awakened and the exception will be signaled; if the exception is resumed, then the receiver will return to a blocked state unless the blocking Semaphore has excess signals" "If we are the active process, go ahead and signal the exception" self isActiveProcess ifTrue: [^anException signal]. "Suspend myself first to ensure that I won't run away in the midst of the following modifications." + self isSuspended ifFalse: + [self suspend]. + suspendedContext ifNil: [self error: 'no suspended context!!!!']. + suspendedContext := Context - self suspend. - suspendedContext := Context sender: suspendedContext receiver: anException method: (anException class lookupSelector: #signal) arguments: #(). + ^self resume! - ^self resume! -- _,,,^..^,,,_ best, Eliot -------------- next part -------------- An HTML attachment was scrubbed... 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