On Apr 22, 2008, at 6:37 AM, Paul Thomas wrote:
I'm trying to implement a basic promise variable and I'm not sure if OSMemoryBarrier() is enough to make it correct. If anyone is familiar with the memory model, I'd appreciate a quick look-over.It's basically like this: { BOOL done; id result; NSError* error; NSException* exception; }Users ask for KVO notifications on 'done' and don't attempt to access any other ivars until done == YES. Then whatever thread or NSOperation or whatever that is responsible for delivering the result calls:-(void)completeWithResult:(id)res { result = res; [self willChangeValueForKey:@"done"]; done = YES; OSMemoryBarrier(); [self didChangeValueForKey:@"done"]; } Is this enough? Or will I need to use a full blown lock?
What is it that you fear going wrong, such that you think even OSMemoryBarrier is necessary?
KVO notifications are delivered on the thread where will/ didChangeValueForKey: are called. There's no multi-threading issue inherent in the above code, even without OSMemoryBarrier.
-Ken _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
