Re: Exact semantics of NSThread executation states?
Re: Exact semantics of NSThread executation states?
- Subject: Re: Exact semantics of NSThread executation states?
- From: "Glenn L. Austin" <email@hidden>
- Date: Tue, 12 Jul 2016 17:05:43 -0700
> On Jul 12, 2016, at 2:52 PM, Sean McBride <email@hidden> wrote:
>
> Hi all,
>
> NSThread has at least 3 execution state properties: executing, finished, cancelled. Alas, the docs don't say much about what they mean beyond circular definitions like "A Boolean value that indicates whether the receiver is executing".
>
> I have code where I create an NSThread, add a runloop source, then invoke "start" on the thread. I have assumed that once I invoke "start" that "isExecuting" should give YES. Literally:
>
> [myThread start];
> assert([myThread isExecuting]);
>
> On 10.11.5 and earlier this *seems* to always be true, but on 10.12b2 it's not. I'm trying to understand if my assumption was wrong or if it's an OS bug.
There's no guarantee that a thread will be running at exit of -[NSThread start] -- only that it has been scheduled for execution. The lower-level pthread APIs also don't guarantee that the thread will start executing when the thread is created.
In reality, there's a fourth state -- scheduled -- that comes before executing. Most of the time you don't need to worry about it.
--
Glenn L. Austin, Computer Wizard and Race Car Driver <><
<http://www.austinsoft.com>
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