static ThreadingTracingInitializer()
{
TaskTrace.Initialize(new TaskTraceCallbacksImplementation());
SpinLockTrace.Initialize(new SpinLockTraceCallbacksImplementation());
}
/// <summary>
/// Try acquire the lock with long path, this is usually called after the first path in Enter and
/// TryEnter failed The reason for short path is to make it inline in the run time which improves the
/// performance. This method assumed that the parameter are validated in Enter ir TryENter method
/// </summary>
/// <param name="millisecondsTimeout">The timeout milliseconds</param>
/// <param name="lockTaken">The lockTaken param</param>
private void ContinueTryEnter(int millisecondsTimeout, ref bool lockTaken)
{
// The fast path doesn't throw any exception, so we have to validate the parameters here
if (lockTaken)
{
lockTaken = false;
throw new System.ArgumentException(SR.SpinLock_TryReliableEnter_ArgumentException);
}
if (millisecondsTimeout < -1)
{
throw new ArgumentOutOfRangeException(
nameof(millisecondsTimeout), millisecondsTimeout, SR.SpinLock_TryEnter_ArgumentOutOfRange);
}
uint startTime = 0;
if (millisecondsTimeout != Timeout.Infinite && millisecondsTimeout != 0)
{
startTime = TimeoutHelper.GetTime();
}
if (SpinLockTrace.Enabled)
{
SpinLockTrace.SpinLock_FastPathFailed(m_owner);
}
if (IsThreadOwnerTrackingEnabled)
{
// Slow path for enabled thread tracking mode
ContinueTryEnterWithThreadTracking(millisecondsTimeout, startTime, ref lockTaken);
return;
}
// then thread tracking is disabled
// In this case there are three ways to acquire the lock
// 1- the first way the thread either tries to get the lock if it's free or updates the waiters, if the turn >= the processors count then go to 3 else go to 2
// 2- In this step the waiter threads spins and tries to acquire the lock, the number of spin iterations and spin count is dependent on the thread turn
// the late the thread arrives the more it spins and less frequent it check the lock avilability
// Also the spins count is increases each iteration
// If the spins iterations finished and failed to acquire the lock, go to step 3
// 3- This is the yielding step, there are two ways of yielding Thread.Yield and Sleep(1)
// If the timeout is expired in after step 1, we need to decrement the waiters count before returning
int observedOwner;
int turn = int.MaxValue;
//***Step 1, take the lock or update the waiters
// try to acquire the lock directly if possible or update the waiters count
observedOwner = m_owner;
if ((observedOwner & LOCK_ANONYMOUS_OWNED) == LOCK_UNOWNED)
{
if (CompareExchange(ref m_owner, observedOwner | 1, observedOwner, ref lockTaken) == observedOwner ||
millisecondsTimeout == 0)
{
// Aquired lock, or did not aquire lock as owned but timeout is 0 so fail fast
return;
}
}
else if (millisecondsTimeout == 0)
{
// Did not aquire lock as owned and timeout is 0 so fail fast
return;
}
else //failed to acquire the lock,then try to update the waiters. If the waiters count reached the maximum, jsut break the loop to avoid overflow
{
if ((observedOwner & WAITERS_MASK) != MAXIMUM_WAITERS)
{
turn = (Interlocked.Add(ref m_owner, 2) & WAITERS_MASK) >> 1;
}
}
//***Step 2. Spinning
//lock acquired failed and waiters updated
int processorCount = PlatformHelper.ProcessorCount;
if (turn < processorCount)
{
int processFactor = 1;
for (int i = 1; i <= turn * SPINNING_FACTOR; i++)
{
SpinWait.Spin((turn + i) * SPINNING_FACTOR * processFactor);
if (processFactor < processorCount)
{
processFactor++;
}
observedOwner = m_owner;
if ((observedOwner & LOCK_ANONYMOUS_OWNED) == LOCK_UNOWNED)
{
int newOwner = (observedOwner & WAITERS_MASK) == 0 ? // Gets the number of waiters, if zero
observedOwner | 1 // don't decrement it. just set the lock bit, it is zzero because a previous call of Exit(false) ehich corrupted the waiters
: (observedOwner - 2) | 1; // otherwise decrement the waiters and set the lock bit
Debug.Assert((newOwner & WAITERS_MASK) >= 0);
if (CompareExchange(ref m_owner, newOwner, observedOwner, ref lockTaken) == observedOwner)
{
return;
}
}
}
// Check the timeout.
if (millisecondsTimeout != Timeout.Infinite && TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout) <= 0)
{
DecrementWaiters();
return;
}
}
//*** Step 3, Yielding
//Sleep(1) every 50 yields
int yieldsoFar = 0;
while (true)
{
observedOwner = m_owner;
if ((observedOwner & LOCK_ANONYMOUS_OWNED) == LOCK_UNOWNED)
{
int newOwner = (observedOwner & WAITERS_MASK) == 0 ? // Gets the number of waiters, if zero
observedOwner | 1 // don't decrement it. just set the lock bit, it is zzero because a previous call of Exit(false) ehich corrupted the waiters
: (observedOwner - 2) | 1; // otherwise decrement the waiters and set the lock bit
Debug.Assert((newOwner & WAITERS_MASK) >= 0);
if (CompareExchange(ref m_owner, newOwner, observedOwner, ref lockTaken) == observedOwner)
{
return;
}
}
if (yieldsoFar % SLEEP_ONE_FREQUENCY == 0)
{
Interop.mincore.Sleep(1);
}
else if (yieldsoFar % SLEEP_ZERO_FREQUENCY == 0)
{
Interop.mincore.Sleep(0);
}
else
{
SpinWait.Yield();
}
if (yieldsoFar % TIMEOUT_CHECK_FREQUENCY == 0)
{
//Check the timeout.
if (millisecondsTimeout != Timeout.Infinite && TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout) <= 0)
{
DecrementWaiters();
return;
}
}
yieldsoFar++;
}
}
/// <summary>
/// Early library initialization code. StartupCodeInjectorTransform emits calls to these methods
/// to startupCodeTrigger.InternalInitialize in the toolchain-generated assembly.
/// BuildDriver.Config defines the ordered list of assemblies to initialize in the method
/// GetLibraryInitializers().
/// </summary>
public static void InitializeLibrary()
{
TaskTrace.Initialize(new TaskTraceCallbacksImplementation());
SpinLockTrace.Initialize(new SpinLockTraceCallbacksImplementation());
}
