On 24.02.2014 18:11, Michael Schnell wrote:
CPI32 (and Fido) has add and sub instruction with memory source and
Target.:-)
The problem is that InterlockedIncrement and -Decrement return the value
after increment/decrement. Thus (with interrupts enabled) there could be
the following problem:
Assume this inline assembly code for InterlockedIncrement (target is the
"var" argument of the function):
lea target, a0
addq.l (a0), 1
move.l (a0), result
move.l result, target
Now there could be an interupt between addq and move and the OS might
decide to run a different thread (in case of Linux or Amiga this is
definitely possible). This other thread *might* do an
InterlockedIncrement for the same variable as well and might also at
least finish the addq instruction. Now the first thread can run again
and the move.l will contain a value after *two* increments. Or worse the
other thread might have done a InterlockedDecrement and now the target
value will be the same as before (keep in mind: var parameter!).
Without the possibility to synchronize the access (I include disabling
interupts here ;) ) there will always be race conditions for
InterlockedIncrement/-Decrement and the other Interlocked* functions.
Regards,
Sven
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