An interface to an abstraction of a work scheduler that wants the Concurrency Runtime's Resource Manager to hand it user-mode schedulable (UMS) threads. The Resource Manager uses this interface to communicate with UMS thread schedulers. The IUMSScheduler interface inherits from the IScheduler interface.
If you are implementing a custom scheduler that communicates with the Resource Manager, and you want UMS threads to be handed to your scheduler instead of ordinary Win32 threads, you should provide an implementation of the IUMSScheduler interface. In addition, you should set the policy value for the scheduler policy key SchedulerKind to be UmsThreadDefault. If the policy specifies UMS thread, the IScheduler interface that is passed as a parameter to the IResourceManager::RegisterScheduler method must be an IUMSScheduler interface.
The Resource Manager is able to hand you UMS threads only on operating systems that have the UMS feature. 64-bit operating systems with version Windows 7 and higher support UMS threads. If you create a scheduler policy with the SchedulerKind key set to the value UmsThreadDefault and the underlying platform does not support UMS, the value of the SchedulerKind key on that policy will be changed to the value ThreadScheduler. You should always read back this policy value before expecting to receive UMS threads.
The IUMSScheduler interface is one end of a two-way channel of communication between a scheduler and the Resource Manager. The other end is represented by the IResourceManager and ISchedulerProxy interfaces, which are implemented by the Resource Manager.