Re: Windows on main thread always only sometimes?
Re: Windows on main thread always only sometimes?
- Subject: Re: Windows on main thread always only sometimes?
- From: Michael Ash <email@hidden>
- Date: Fri, 3 Jul 2009 00:09:31 -0400
On Thu, Jul 2, 2009 at 2:16 PM, Jack Repenning<email@hidden> wrote:
> I've always been taught that one must only create and run AppKit objects on
> the main thread. Recently, though, over in objc-language,
>
> http://lists.apple.com/archives/Objc-language/2009/Jul/msg00002.html
>
> it was pointed out that the threading Programming Guide seems to say
> otherwise:
>
>>
>> <http://developer.apple.com/documentation/Cocoa/Conceptual/Multithreading/ThreadSafetySummary/ThreadSafetySummary.html>
>> says:
>> "You can create a window on a secondary thread. The Application Kit
>> ensures that the data structures associated with a window are deallocated on
>> the main thread to avoid race conditions. There is some possibility that
>> window objects may leak in an application that deals with a lot of windows
>> concurrently. You can create a modal window on a secondary thread. The
>> Application Kit blocks the calling secondary thread while the main thread
>> runs the modal loop."
>
> But now I notice this only says you can *create* windows from secondary
> threads; it doesn't explicitly allow any other action, and it even refers to
> several automatic insurances that other things happen on the main thread.
>
> So what *are* the rules? Is the Thread Safety Summary implicitly strict,
> "you can create a window, but absolutely nothing else"? Or is there some set
> of other operations that are permitted from the secondary (and where do I
> learn those)?
The ironclad rule of thread safety is that if it's not *explicitly*
documented to be thread safe, then it's not.
Thus, all of these other things that the docs don't explicitly refer
to aren't safe to do.
Mike
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