Re: LuaTask needs your help

[David Given <dg@...>]

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Thomas Lauer wrote:
[...]
>>         if( aTask[i]->running) { // <--- aTask pointer may have been
>> realloc()'ed elsewhere
[...]
> I am not sure that this line is indeed a problem. Isn't checking an int
> an atomic operation? As aTask is declared volatile, it should be
> re-referenced, so a change during the loop would not be a problem
> either.

Ah, but that's not an atomic operation. That line compiles into something like:

; r1 contains i
r0 = aTask            ; fetch aTask
r2 = r1 << 2          ; calculate offset into array
r0 = r0 + r2          ; calculate address of pointer in array
r0 = [r0+0]           ; dereference pointer to get address of structure
r0 = [r0+42]          ; fetch structure member

So if aTask gets modified while this code is in operation, suddenly you'll be
working with a stale pointer. Hilarity ensues.

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