Increment is not atomic on most processors, including x86 (inc
[someAddress] does not exist).
Andrei
On 11/1/10 12:49 PM, David Simcha wrote:
On Mon, Nov 1, 2010 at 1:39 PM, Michel Fortin <[email protected]
<mailto:[email protected]>> wrote:
Is "i++" really atomic when i is a size_t? I though it was a
read-modify-write operation. The read might be atomic, the write
might be atomic, but the whole isn't. And in addition to atomicity,
it needs to be sequentially consistent unless we change the GC to
keep threads frozen while calling the destructors.
In theory it could be read-modify-write because you never know if some
incredibly stupid compiler will do something like:
mov EAX, [someAddress];
inc EAX;
mov [someAddress], EAX;
instead of just:
inc [someAddress];
However, I'm pretty sure the second form is atomic, and even if it's not
formally guaranteed, any reasonable compiler would use the single inc
instruction form.
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