----- Original message -----
From: David P Grove/Watson/IBM
To: Philippe Hausler <phaus...@apple.com>
Cc: Mamatha Busi <mamab...@in.ibm.com>, swift-corelibs-dev@swift.org
Subject: Re: [swift-corelibs-dev] Setting property "maxConcurrentOperationCount = 1" of NSOperation fails to execute operations using OpenSource Foundation.
Date: Fri, May 6, 2016 8:12 PM
I think the intuition about the dispatch overlay being the problem on Linux is right on. We may have to hack around the problem on the Foundation side until an improved overlay is available to use.
--davePhilippe Hausler via swift-corelibs-dev ---05/06/2016 09:43:06 AM---I have a feeling this is associated with the changes for IUO types that recently landed. I am very w
From: Philippe Hausler via swift-corelibs-dev <swift-corelibs-dev@swift.org>
To: Mamatha Busi <mamab...@in.ibm.com>
Cc: swift-corelibs-dev@swift.org
Date: 05/06/2016 09:43 AM
Subject: Re: [swift-corelibs-dev] Setting property "maxConcurrentOperationCount = 1" of NSOperation fails to execute operations using OpenSource Foundation.
Sent by: swift-corelibs-dev-boun...@swift.org
I have a feeling this is associated with the changes for IUO types that recently landed. I am very worried that this actually could happen on Darwin targets as well. Perhaps it is the swift overlay for dispatch that is correcting the failure on Darwin and the dispatch on Linux is missing that annotation. Worth looking into.
Sent from my iPhone
On May 6, 2016, at 12:16 AM, Mamatha Busi <mamab...@in.ibm.com> wrote:
@ Philippe: Your right. Converting the 'attr' to an optional did do the job of creating a serial queue successfully. Thanks for that. I will create a PR for this.
But this makes me think as to why until now, this was not caught by the compiler itself?
Regards
Mamatha
- ----- Original message -----
From: phaus...@apple.com
To: Mamatha Busi/India/IBM@IBMIN
Cc: swift-corelibs-dev <swift-corelibs-dev@swift.org>
Subject: Re: [swift-corelibs-dev] Setting property "maxConcurrentOperationCount = 1" of NSOperation fails to execute operations using OpenSource Foundation.
Date: Thu, May 5, 2016 10:54 PM
Hmm that seems unfortunate. I wonder if the serial creation is due to an unwrapped optional? var attr: dispatch_queue_attr_t? instead might do the trick… or alternatively we could just let the underlying queue be concurrent all the time and enforce the max ops via making the semaphore always instantiated (in the case of max ops being 1) and initializing it to 1 to gate the operations.
- On May 5, 2016, at 1:15 AM, Mamatha Busi via swift-corelibs-dev <swift-corelibs-dev@swift.org> wrote:
Hello
Code snippet:
———————————————————————
let operation1 : NSBlockOperation = NSBlockOperation (block: {
sleep(1)
print("Opertion1")
})
let operation2 : NSBlockOperation = NSBlockOperation (block: {
sleep(1)
print("Opertion2”)
})
var operations = [NSOperation]()
operations.append(operation1)
operations.append(operation2)
let queue = NSOperationQueue()
queue.maxConcurrentOperationCount = 1
queue.addOperations(operations, waitUntilFinished: true)
————————————————————————
The above code snippet of adding operations to an operation queue and executing with the property ‘maxConcurrentOperationCount = 1’ fails while executing the above with the OpenSource Foundation and libDispatch of MAC inside Xcode.
The error I am seeing is:
fatal error: unexpectedly found nil while unwrapping an Optional value
Stack trace points to: attr = DISPATCH_QUEUE_SERIAL
which implies that the libDispatch macro is coming as nil during the creation of the serial queue using libDispatch in the file NSOperationQueue
The same test-case passes on OSx.
When I do not restrict the serial operation i.e. I remove ‘ queue.maxConcurrentOperationCount = 1’ , test case executes successfully.
Setting it to a different value other than 1 also causes no problems.
Am I doing something wrong with the API. If I set the property ‘ queue.maxConcurrentOperationCount = 1’ after adding operations to the queue, then the problem does not occur. But then this restricts me to control the operation execution to be serial. So, I expect the above snippet to work on OpenSource as well. Any thoughts on this?
Thank you.
Regards
Mamatha
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