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IVirtualProcessorRoot::Deactivate Method

Causes the thread proxy currently executing on this virtual processor root to stop dispatching the execution context. The thread proxy will resume executing on a call to the Activate method.

virtual bool Deactivate(
   _Inout_ IExecutionContext * pContext
) =0;

pContext

The context which is currently being dispatched by this root.

A boolean value. A value of true indicates that the thread proxy returned from the Deactivate method in response to a call to the Activate method. A value of false indicates that the thread proxy returned from the method in response to a notification event in the Resource Manager. On a user-mode schedulable (UMS) thread scheduler, this indicates that items have appeared on the scheduler's completion list, and the scheduler is required to handle them.

Use this method to temporarily stop executing a virtual processor root when you cannot find any work in your scheduler. A call to the Deactivate method must originate from within the Dispatch method of the execution context that the virtual processor root was last activated with. In other words, the thread proxy invoking the Deactivate method must be the one that is currently executing on the virtual processor root. Calling the method on a virtual processor root you are not executing on could result in undefined behavior.

A deactivated virtual processor root may be woken up with a call to the Activate method, with the same argument that was passed in to the Deactivate method. The scheduler is responsible for ensuring that calls to the Activate and Deactivate methods are paired, but they are not required to be received in a specific order. The Resource Manager can handle receiving a call to the Activate method before it receives a call to the Deactivate method it was meant for.

If a virtual processor root awakens and the return value from the Deactivate method is the value false, the scheduler should query the UMS completion list via the IUMSCompletionList::GetUnblockNotifications method, act on that information, and then subsequently call the Deactivate method again. This should be repeated until such time as the Deactivate method returns the value true.

invalid_argument is thrown if the argument pContext has the value NULL.

invalid_operation is thrown if the virtual processor root has never been activated, or the argument pContext does not represent the execution context that was most recently dispatched by this virtual processor root.

The act of deactivating a virtual processor root decreases the subscription level of the underlying hardware thread by one. For more information on subscription levels, see IExecutionResource::CurrentSubscriptionLevel.

Header: concrtrm.h

Namespace: concurrency

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