[Gllug] Atomic increment/decrement

[t.clarke]

I have no ideas about mutexes - never fortunately had the need.

But I do remember many years ago having to do something vaguely similar on
a TI990 computer.

As I recall, the fundamental issue was one of getting the CPU to do an atomic
operation (of any sort) by first using a atomic 'test and set' cpu opcode.
The routine was in assembler and did something along the lines of
test and set a flag word
if the set succeeded you have control so do the atomic operation
and reset the flag word
if no success spin for a bit and try again

The whole thing depended on an atomic cpu test-and-set instruction and was
written in assembler.

I assume that unless the C language supports such a test-and-set cpu instruction
directly, you will have do write something in assembler to gain access to the
Intel X86 opcodes directly.


Tim

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