[swift-dev] Thread safety of weak properties

[Greg Parker]

> On Dec 14, 2015, at 9:47 AM, John McCall via swift-dev <swift-dev at swift.org> wrote:
> 
>> On Dec 12, 2015, at 7:04 PM, Chris Lattner <clattner at apple.com> wrote:
>> #3 sounds like a great approach to me.  I agree with Kevin that if we keep the object husk approach that any use of a weak pointer that returns nil should drop any reference to a husk.
> 
> Spin locks are, unfortunately, illegal on iOS, which does not guarantee progress in the face of priority inversion.

There is a spinlock algorithm that does work (in practice if not in theory), but it requires a full word of storage instead of a single bit.


-- 
Greg Parker     gparker at apple.com     Runtime Wrangler