public override void AddRunnableThread(Thread thread)
{
ThreadState newState;
// Change thread's state to runnable: Runpolicy will decide latter on
// if it can actually run the thread
newState = thread.ChangeSchedulerState(ThreadState.Runnable);
// Add thread to runnable queue only if new state is runnable
if (newState == ThreadState.Runnable)
{
// While we adding a thread to runnable queue someone could have called freeze on
// it again - RunPolicy will notice it and remove thread from runnable queue appropriatly
this.unblockedThreads.EnqueueTail(thread.schedulerEntry);
}
}
public override Thread RunPolicy(
int affinity,
Thread currentThread,
ThreadState schedulerAction,
SchedulerTime currentTime)
{
Thread threadToReturn = null;
ThreadState newState = ThreadState.Undefined;
ThreadEntry entry = null;
// Put current thread on a runnable queue only if it is currently in a running state
if (currentThread != null)
{
// At this point current threads state has to be
// running - when running derived scheduler state we will deduce new state
// but until then it has to be running
VTable.Assert(currentThread.ThreadState == ThreadState.Running);
// If scheduler action is running make it runnable to have proper state transition
// Currently we disallow to go from running to running
if (schedulerAction == ThreadState.Running)
{
schedulerAction = ThreadState.Runnable;
}
// Change current's thread new scheudler state
newState = currentThread.ChangeSchedulerState(schedulerAction);
// If new state is runnable add it to runnable queue
if (newState == ThreadState.Runnable)
{
// REVIEW: Should we make sure the thread is enqueue already?
// Indicate that thread has been marked as runnable
this.runnableThreads.EnqueueTail(currentThread.schedulerEntry);
}
}
// Derived state of entry on the runnable queue can be either suspended or runnable.
// Consequently first we remove an entry from the queue. If it is runnable,
// we will be able to convert it to running, If it is suspended,
// we will convert its real state to suspended. The first thread that marks the entry
// unsuspended will be responsible for putting it on back on a runnable queue.
// Check the unblocked queue first.
while ((entry = this.unblockedThreads.DequeueHead()) != null)
{
// At this point thread direct state can be only runnable...
VTable.Assert(entry.Thread.IsRunnable);
// Attempt to make thread running
newState = entry.Thread.ChangeSchedulerState(ThreadState.Running);
// Get of the loop if we marked one of the entries as running
if (newState == ThreadState.Running)
{
break;
}
// If the thread is suspended, then look for another.
VTable.Assert(newState == ThreadState.Suspended);
}
// If no recently unblocked threads, then check the runnable queue.
if (entry == null)
{
while ((entry = this.runnableThreads.DequeueHead()) != null)
{
// At this point thread direct state can be only runnable...
VTable.Assert(entry.Thread.IsRunnable);
// Attempt to make thread running
newState = entry.Thread.ChangeSchedulerState(ThreadState.Running);
// Get of the loop if we marked one of the entries as running
if (newState == ThreadState.Running)
{
break;
}
// If the thread is suspended, then look for another.
VTable.Assert(newState == ThreadState.Suspended);
}
}
// We got an entry from the runnable queue that we can actually run.
if (entry != null)
{
// Thread must realy by in the running state.
VTable.Assert(newState == ThreadState.Running);
// Initialize thread we about to return.
threadToReturn = entry.Thread;
threadToReturn.Affinity = affinity;
}
return(threadToReturn);
}
