is +=1 thread safe

[John Nagle]

AlFire wrote:
> Hi,
> all is very simple and by the end of the program life I expect the 
> counter to zero out.
> 
> however I am getting values -1, -2, 1 ,2 ,3 and quite often 0 as expected.
> 
> I guarded those statement with Lock.{acquire,release} and now it always 
> returns 0.
> 
> 
> But I still can not believe that +=1 is not a thread safe operation.
> 
> 
> Any clue?

    "counter += 1" is not an atomic operation, apparently.  Sorry.

    However, appending and removing from a list or dict are atomic operations,
because if they were not, memory allocation would break.

						John Nagle