review request (M): 7121140: Allocation paths require explicit memory synchronization operations for RMO systems

Tom Rodriguez tom.rodriguez at
Wed Dec 14 11:41:33 PST 2011

On Dec 14, 2011, at 7:55 AM, Roland Westrelin wrote:

> For systems that don't implement total store ordering a store store barrier is required after a newly allocated objects is initialized and before it becomes globally reachable.

I think the instruct name should be membar_storestoree instead of unnecessary_membar_storestore and remove the "unnecessary so" part of the comment.  It's like membar_release where it's necessary but it never emits any assembly.

I wouldn't expect this to affect performance since it's not emitting an extra instructions but we are emitting some extra barriers which tangles of the memory graph a bit.  Could you do some quick performance to make sure nothing's changed?

Otherwise it looks good.


> Roland.

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