Oh. Interesting observation. Sounds right to me. Guess we'll have to add a checkForInterrupts() to callbackEnter. BTW, this strongly resonates with what I was writing about the event driven VM. In that scheme "callbackEnter" would be a straightforward call to interpret().

Cheers, - Andreas

John M McIntosh wrote:

Since we are talking about events, this is an error thrown by a iphone squeak vm setup as a single pthread.

What happens is ioGetNextEvent is called which calls ioProcessEvents which on a special version of the iphone vm calls [NSRunLoop currentRunLoop] to run for N milliseconds.

When the run loop runs it ends up sending a message to an Objective-C SqueakProxy instance which then signals a squeak semaphore to wake up the VM. In this specialized VM it does

    interpreterProxy->signalSemaphoreWithIndex(sem);
    interpreterProxy->callbackEnter(&callbackid);

However I *think* the problem here is that although we signal the semaphore then issue the forceInterruptCheck in callbackEnter: this does not actually alter the runnable processes list since that work is only done when checkForInterrrupts() is run. Thus in this case the only process running is the idleProcess, and it's sleeping but we are attempting to wake a squeakProxy process waiting on the semaphore we did signal, but as you see oops nada runnable, so die.

2009-11-10 12:59:36.214 x[13886:207] forwardInvocation: <NSInvocation: 0x1368370> 2009-11-10 12:59:36.215 x[13886:207] currentThread: <NSThread: 0x1105e90>{name = (null), num = 1} 2009-11-10 12:59:36.219 x[13886:207] inside lock 0 2009-11-10 12:59:36.220 x[13886:207] signalling squeak

scheduler could not find a runnable process

548435824 >idleProcess 548435732 >startUp 548291060 BlockClosure>newProcess

callbackEnter: callbackID "Re-enter the interpreter for executing a callback" | result activeProc | self export: true. self var: #callbackID declareC: 'sqInt *callbackID'.

"For now, do not allow a callback unless we're in a primitiveResponse"
primitiveIndex = 0 ifTrue:[^false].

"Check if we've exceeded the callback depth"
jmpDepth >= jmpMax ifTrue:[^false].
jmpDepth := jmpDepth + 1.

"Suspend the currently active process"
activeProc := self fetchPointer: ActiveProcessIndex
                     ofObject: self schedulerPointer.
suspendedCallbacks at: jmpDepth put: activeProc.
"We need to preserve newMethod explicitly since it is not activated yet
and therefore no context has been created for it. If the caller 

primitive for any reason decides to fail we need to make sure we execute the correct method and not the one 'last used' in the call back" suspendedMethods at: jmpDepth put: newMethod. self transferTo: self wakeHighestPriority.

"Typically, invoking the callback means that some semaphore has been
signaled to indicate the callback. Force an interrupt check right 

away." self forceInterruptCheck.

result := self setjmp: (jmpBuf at: jmpDepth).
result == 0 ifTrue:["Fill in callbackID"
    callbackID at: 0 put: jmpDepth.
    "This is ugly but the inliner treats interpret() in very special 

and strange ways and calling any kind of 'self interpret' either directly or even via cCode:inSmalltalk: will cause this entire method to vanish." self cCode: 'interpret()'. ].

"Transfer back to the previous process so that caller can push result"
activeProc := self fetchPointer: ActiveProcessIndex
                     ofObject: self schedulerPointer.
self putToSleep: activeProc.
activeProc := suspendedCallbacks at: jmpDepth.
newMethod := suspendedMethods at: jmpDepth.    "see comment above"
self transferTo: activeProc.
jmpDepth := jmpDepth-1.
^true

--

John M. McIntosh johnmci@smalltalkconsulting.com Twitter: squeaker68882 Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com ===========================================================================