public void Post(IOThreadScheduler iots)
{
Fx.Assert(_scheduler == null, "Post called on an overlapped that is already posted.");
Fx.Assert(iots != null, "Post called with a null scheduler.");
_scheduler = iots;
_postDelegate();
}
public void Post(IOThreadScheduler iots)
{
Fx.Assert(scheduler == null, "Post called on an overlapped that is already posted.");
Fx.Assert(iots != null, "Post called with a null scheduler.");
scheduler = iots;
ThreadPool.UnsafeQueueNativeOverlapped(nativeOverlapped);
}
// Returns true if successfully scheduled, false otherwise.
bool ScheduleCallbackLowPriHelper(Action <object> callback, object state)
{
// See if there's a free slot. Fortunately the overflow bit is simply lost.
int slot = Interlocked.Add(ref headTailLowPri, Bits.HiOne);
// If this is the first low-priority work item, make sure we're not idle.
bool wasIdle = false;
if (Bits.CountNoIdle(slot) == 1)
{
// Since Interlocked calls create a full thread barrier, this will read the value of headTail
// at the time of the Interlocked.Add or later. The invariant is that the IOTS is unidle at some
// point after the Add.
int ht = headTail;
if (Bits.Count(ht) == -1)
{
// Use a temporary local here to store the result of the Interlocked.CompareExchange. This
// works around a codegen bug in the 32-bit JIT (TFS 749182).
int interlockedResult = Interlocked.CompareExchange(ref headTail, ht + Bits.HiOne, ht);
if (ht == interlockedResult)
{
wasIdle = true;
}
}
}
// Check if we wrapped *around* to empty.
if (Bits.CountNoIdle(slot) == 0)
{
// Since the capacity is limited to 32k, this means we wrapped the array at least twice. That's bad
// because headTail no longer knows how many work items we have - it looks like zero. This can
// only happen if 32k threads come through here while one is swapped out.
throw Fx.AssertAndThrowFatal("Low-priority Head/Tail overflow!");
}
bool wrapped;
bool queued = slotsLowPri[slot >> Bits.HiShift & SlotMaskLowPri].TryEnqueueWorkItem(
callback, state, out wrapped);
if (wrapped)
{
IOThreadScheduler next =
new IOThreadScheduler(slots.Length, Math.Min(slotsLowPri.Length * 2, MaximumCapacity));
Interlocked.CompareExchange <IOThreadScheduler>(ref IOThreadScheduler.current, next, this);
}
if (wasIdle)
{
// It's our responsibility to kick off the overlapped.
overlapped.Post(this);
}
return(queued);
}
static void ScheduleCallback(Action <object> callback, object state, bool lowPriority)
{
Fx.Assert(callback != null, "Cannot schedule a null callback");
if (lowPriority)
{
IOThreadScheduler.ScheduleCallbackLowPriNoFlow(callback, state);
}
else
{
IOThreadScheduler.ScheduleCallbackNoFlow(callback, state);
}
}
// Returns true if successfully scheduled, false otherwise.
bool ScheduleCallbackHelper(Action <object> callback, object state)
{
// See if there's a free slot. Fortunately the overflow bit is simply lost.
int slot = Interlocked.Add(ref headTail, Bits.HiOne);
// If this brings us to 'empty', then the IOTS used to be 'idle'. Remember that, and increment
// again. This doesn't need to be in a loop, because until we call Post(), we can't go back to idle.
bool wasIdle = Bits.Count(slot) == 0;
if (wasIdle)
{
slot = Interlocked.Add(ref headTail, Bits.HiOne);
Fx.Assert(Bits.Count(slot) != 0, "IOTS went idle when it shouldn't have.");
}
// Check if we wrapped *around* to idle.
if (Bits.Count(slot) == -1)
{
// Since the capacity is limited to 32k, this means we wrapped the array at least twice. That's bad
// because headTail no longer knows how many work items we have - it looks like zero. This can
// only happen if 32k threads come through here while one is swapped out.
throw Fx.AssertAndThrowFatal("Head/Tail overflow!");
}
bool wrapped;
bool queued = slots[slot >> Bits.HiShift & SlotMask].TryEnqueueWorkItem(callback, state, out wrapped);
if (wrapped)
{
// Wrapped around the circular buffer. Create a new, bigger IOThreadScheduler.
IOThreadScheduler next =
new IOThreadScheduler(Math.Min(slots.Length * 2, MaximumCapacity), slotsLowPri.Length);
Interlocked.CompareExchange <IOThreadScheduler>(ref IOThreadScheduler.current, next, this);
}
if (wasIdle)
{
// It's our responsibility to kick off the overlapped.
overlapped.Post(this);
}
return(queued);
}
void IOCallback(uint errorCode, uint numBytes, NativeOverlapped *nativeOverlapped)
{
// Unhook the IOThreadScheduler ASAP to prevent it from leaking.
IOThreadScheduler iots = scheduler;
scheduler = null;
Fx.Assert(iots != null, "Overlapped completed without a scheduler.");
Action <object> callback;
object state;
try { }
finally
{
// Called in a finally because it needs to run uninterrupted in order to maintain consistency.
iots.CompletionCallback(out callback, out state);
}
bool found = true;
while (found)
{
// The callback can be null if synchronization misses result in unsuable slots. Keep going onto
// the next slot in such cases until there are no more slots.
if (callback != null)
{
callback(state);
}
try { }
finally
{
// Called in a finally because it needs to run uninterrupted in order to maintain consistency.
found = iots.TryCoalesce(out callback, out state);
}
}
}
public override void Post(SendOrPostCallback d, object state)
{
IOThreadScheduler.ScheduleCallbackNoFlow(
(s) => { d(s); }, state);
}