Morphic yellow cross of death

I'll think about this some more, but my current suspicion centers on:

styleInBackgroundProcess: aText

    self terminateBackgroundStylingProcess.
    stylingEnabled ifTrue:[
        text := aText copy.
        self monitor critical: [
            sem := Semaphore new.
            [sem notNil
                ifTrue: [
                    sem wait.
                    view ifNotNil:[view stylerStyledInBackground: text]]
            ] forkAt: Processor activePriority.
            backgroundProcess :=
                [self privateStyle: text.
                sem signal]
                    forkAt: Processor userBackgroundPriority] ]
   
I'm a little concerned about the

            ] forkAt: Processor activePriority.

resulting in a process (1) running at the same priority as the UI process and (2) that will modify the state of a text morph on the screen. If such a modification is interrupted by a higher-priority process, the resumed process will not be the interrupted one, but the UI process which may proceed to display the world, includeing the partially modified text morph.

If you can figure out how to make the error happen easily, then things to try:
- increase the priority a bit
            [sem notNil
                ifTrue: [
                    sem wait.
                    view ifNotNil:[view stylerStyledInBackground: text]]
            ] forkAt: Processor activePriority+1.
- use
    WorldState addDeferredUIMessage: [view ifNotNil:[view stylerStyledInBackground: text]]
instead of a separate process
- disable background styling

One or more of these might make the problem go away. Assuming you can force the problem to happen reliably. ;-)


Cheers,
Bob

I was trying to merge tim's change with mine, so the image was definitely not clean.
This involved many action, correcting SyntaxError, etc... breaking an image, killing the process, and restarting all over again.

If I remember, I got such error first in a MC merge window.

I also remember some strange warning 'This modal dialog was interrupted, please close it'... This could be from MCTool answer:

Generally, the red squeare is not solitary, they like to burst in flock, so I suspect some ill state of the World, like having several UI processes? But currently my image show no extra Process in the ProcessBrowser

2013/9/24 Bob Arning <[hidden email]>

One more question:

- Were there any processes running other than those standard in all Squeaks?

Cheers,
Bob

On 9/23/13 7:43 PM, Nicolas Cellier wrote:

After replacing doOneCycle with displayWorldSafely, I got much more stable morphs...

But see yet another red square attached...

2013/9/18 Bob Arning <[hidden email]>

So, the question is do they really need #doOneCycle or something less, like #displayWorldSafely

Cheers,
Bob

On 9/17/13 6:36 PM, Nicolas Cellier wrote:

Ah we cross posted, good find!

Those guys messing with World doOneCycle are just like the sorcerer's apprentice...

One thing that would help for next time would be saving all the stack traces (especially the first one). There used to be a preference #appendToErrorLog that did just that. Easy enough to add: just don't delete the old squeakdebug.log and do a #setToEnd before writing. As it stands, the stack trace we have doesn't say anything about how that text morph got that way. Perhaps an earlier, more significant, error was overwritten and that would have told us something.

Cheers,
Bob

I was trying to merge tim's change with mine, so the image was definitely not clean.
This involved many action, correcting SyntaxError, etc... breaking an image, killing the process, and restarting all over again.

If I remember, I got such error first in a MC merge window.

I also remember some strange warning 'This modal dialog was interrupted, please close it'... This could be from MCTool answer:

Generally, the red squeare is not solitary, they like to burst in flock, so I suspect some ill state of the World, like having several UI processes? But currently my image show no extra Process in the ProcessBrowser

2013/9/24 Bob Arning <[hidden email]>

One more question:

- Were there any processes running other than those standard in all Squeaks?

Cheers,
Bob

On 9/23/13 7:43 PM, Nicolas Cellier wrote:

After replacing doOneCycle with displayWorldSafely, I got much more stable morphs...

But see yet another red square attached...

2013/9/18 Bob Arning <[hidden email]>

So, the question is do they really need #doOneCycle or something less, like #displayWorldSafely

Cheers,
Bob

On 9/17/13 6:36 PM, Nicolas Cellier wrote:

Ah we cross posted, good find!

Those guys messing with World doOneCycle are just like the sorcerer's apprentice...

I've inserted a delay in TextMorph>>paragraph when not running in the ui process to simulate getting interrupted while building the new paragraph and it does recreate your errors, including the warning message from MC. I still have not convinced myself that such an interrupt is a high enough probability to account for the number of times you have seen this error. But, perhaps some combination of factors in your image make it more likely. In any event, I think moving the actual updating of the TextMorph to the UI process would be a good thing on general principles.

Cheers,
Bob

I was trying to merge tim's change with mine, so the image was definitely not clean.
This involved many action, correcting SyntaxError, etc... breaking an image, killing the process, and restarting all over again.

If I remember, I got such error first in a MC merge window.

I also remember some strange warning 'This modal dialog was interrupted, please close it'... This could be from MCTool answer:

Generally, the red squeare is not solitary, they like to burst in flock, so I suspect some ill state of the World, like having several UI processes? But currently my image show no extra Process in the ProcessBrowser

2013/9/24 Bob Arning <[hidden email]>

One more question:

- Were there any processes running other than those standard in all Squeaks?

Cheers,
Bob

On 9/23/13 7:43 PM, Nicolas Cellier wrote:

After replacing doOneCycle with displayWorldSafely, I got much more stable morphs...

But see yet another red square attached...

2013/9/18 Bob Arning <[hidden email]>

So, the question is do they really need #doOneCycle or something less, like #displayWorldSafely

Cheers,
Bob

On 9/17/13 6:36 PM, Nicolas Cellier wrote:

Ah we cross posted, good find!

Those guys messing with World doOneCycle are just like the sorcerer's apprentice...