On Thu, Mar 09, 2017 at 12:41:44PM -0800, Eliot Miranda wrote:
Hi David,
On Mon, Mar 6, 2017 at 5:50 PM, David T. Lewis lewis@mail.msen.com wrote:
In the VM, the millisecond clock wraps within the 32 bit integer range:
#define MillisecondClockMask 0x1FFFFFFF
In the Cuis image, Delay class>>handleTimerEvent does this:
nextTick := nextTick min: SmallInteger maxVal.
On a 64-bit Spur image, SmallInteger maxVal is 16rFFFFFFFFFFFFFFF, but on a 32-bit image it is 16r3FFFFFFF.
Could that be it?
I don't really know how to test in Squeak. As you say, Squeak is now using the microsecond clock in #handleTimerEvent. I do not see anything in primitiveSignalAtMilliseconds that would behave any differently on a 64 bit versus 32 bit image or VM, but I do not know how to test to be sure.
I bet that the following code from primitiveSignalAtMilliseconds ends up wrapping when given Delay primSignal: s atMilliseconds: Time primMillisecondClock - 10.
deltaMsecs := msecs - (self ioMSecs bitAnd: MillisecondClockMask). deltaMsecs < 0 ifTrue: [deltaMsecs := deltaMsecs + MillisecondClockMask + 1]. nextWakeupUsecs := self ioUTCMicroseconds + (deltaMsecs * 1000).
and I bet you'll find that the VM will wake up in about 6 days and 5 hours ;-)
No. The failure is specific to the 64 bit VM. Source code for the primitive is the same in either case.
I suppose we could fix this, but I'm *much* happier to simply not use primitiveSignalAtMilliseconds and stay with the simpler and wrapping-immune primitiveSignalAtUTCMicroseconds
Fair enough, but given that there is a demonstrated bug that affects only the 64-bit VM, and given that it expresses itself intermittently and in ways that affect only someone who is attempting to migrate their existing V3 image to Spur, then I would say that it makes very good sense to take the time to fix it if we are able to do so. After all, there may be other people who will want to migrate V3 images to Spur, and there is no point in making the process needlessly difficult.
I do not have the solution, but maybe someone else can help. So I am asking for help here. Can someone with a working 64-bit build environment please check and see if what I said in an earlier email might make a difference:
I see that ioMSecs() is declared as signed long (32 bits), but it is used in expression with a 64 bit usqInt. So maybe it needs a cast, or maybe the variables like msecs and deltaMsecs in primitiveSignalAtMilliseconds should be declared as 32 bit long and unsigned long to match the actual usage.
Thanks,
Dave