Do NSOperations and their completionBlocks run concurrently?
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I've got a bunch of NSOperations added to a NSOperationQueue. The operation queue has the maxConcurrentOperationCount set to 1, so that the NSOperations run one after the other.

Now, in the completionBlock of a NSOperation I want to cancel all pending NSOperations by calling cancelAllOperations on the NSOperationQueue. 

Is it safe to do this? Can I be sure that the start-method of the next operation is called only after the completionBlock of the previous operation has been fully executed? Or do the completionBlock of the previous operation and the task of the current operation run concurrently?

The reason why I'm asking: I use AFNetworking to execute a batch of AFHTTPRequestOperations and want to perform one request only if all previous requests of the batch were successful.