Re: How is my CFRunLoopTimer getting called during a CFReadStream client callback?
Re: How is my CFRunLoopTimer getting called during a CFReadStream client callback?
- Subject: Re: How is my CFRunLoopTimer getting called during a CFReadStream client callback?
- From: "Jim O'Connor" <email@hidden>
- Date: Sun, 05 Jan 2014 16:02:45 -0900
I punctuated that poorly.
I can run the CFRunLoop myself. Or it is (nearly) the top level for the thread, typically.
It shouldn't be the case that timers fire other than with a CFRunLoop() just above them in the stack, though, right?
As I said, it was really late after a long long day, so maybe I didn't read it correctly. I should have saved off the stack crawl. At this point I want to be sure I don't have a fundamental misunderstanding of something I thought was a constant, though. If the OS is going to call the runloop on me it should change the mode.
Thanks for the reply.
Jim
On Jan 5, 2014, at 3:47 PM, Kyle Sluder <email@hidden> wrote:
> On Jan 5, 2014, at 4:37 PM, Jim O'Connor <email@hidden> wrote:
>>
>> When my read stream finishes I schedule a timer to clean up on the runloop to serialize access to shared resources.
>> However, I had a hang late last night because a mutex grabbed in the read stream callback handler was held and was also being grabbed when the timer it scheduled to clean up fired INSIDE the callback.
>> It was late and I didn't save the odd message in the Xcode stack crawl about the timer being called OUTSIDE of the runloop. And now I can't get it to repeat.
>>
>> I was under the impression that timers only fired when the RunLoop was actually the top of the execution stack, or was called explicitly by me. Is this not right?
>
> Well, barring a memory smasher, CFReadStream isn’t going to directly invoke your timer callback function.
>
> But your use of “top of the execution stack” seems a little off to me. It’s possible to manually run a runloop from a deeper stack frame; this is often done by APIs which present a callback interface but need to use asynchrony internally.
>
> The run loop doesn’t care that it’s being run from code that itself is being indirectly called as a result of a turn of the same run loop, so it will fire its timers just like normal.
>
> --Kyle Sluder
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