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#pragma warning disable 0420
// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// SlimManualResetEvent.cs
//
// <OWNER>Microsoft</OWNER>
//
// An manual-reset event that mixes a little spinning with a true Win32 event.
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
using System;
using System.Diagnostics;
using System.Security.Permissions;
using System.Threading;
using System.Runtime.InteropServices;
using System.Diagnostics.Contracts;
namespace System.Threading
{
// ManualResetEventSlim wraps a manual-reset event internally with a little bit of
// spinning. When an event will be set imminently, it is often advantageous to avoid
// a 4k+ cycle context switch in favor of briefly spinning. Therefore we layer on to
// a brief amount of spinning that should, on the average, make using the slim event
// cheaper than using Win32 events directly. This can be reset manually, much like
// a Win32 manual-reset would be.
//
// Notes:
// We lazily allocate the Win32 event internally. Therefore, the caller should
// always call Dispose to clean it up, just in case. This API is a no-op of the
// event wasn't allocated, but if it was, ensures that the event goes away
// eagerly, instead of waiting for finalization.
/// <summary>
/// Provides a slimmed down version of <see cref="T:System.Threading.ManualResetEvent"/>.
/// </summary>
/// <remarks>
/// All public and protected members of <see cref="ManualResetEventSlim"/> are thread-safe and may be used
/// concurrently from multiple threads, with the exception of Dispose, which
/// must only be used when all other operations on the <see cref="ManualResetEventSlim"/> have
/// completed, and Reset, which should only be used when no other threads are
/// accessing the event.
/// </remarks>
[ComVisible(false)]
[DebuggerDisplay("Set = {IsSet}")]
[HostProtection(Synchronization = true, ExternalThreading = true)]
public class ManualResetEventSlim : IDisposable
{
// These are the default spin counts we use on single-proc and MP machines.
private const int DEFAULT_SPIN_SP = 1;
private const int DEFAULT_SPIN_MP = SpinWait.YIELD_THRESHOLD;
private volatile object m_lock;
// A lock used for waiting and pulsing. Lazily initialized via EnsureLockObjectCreated()
private volatile ManualResetEvent m_eventObj; // A true Win32 event used for waiting.
// -- State -- //
//For a packed word a uint would seem better, but Interlocked.* doesn't support them as uint isn't CLS-compliant.
private volatile int m_combinedState; //ie a UInt32. Used for the state items listed below.
//1-bit for signalled state
private const int SignalledState_BitMask = unchecked((int)0x80000000);//1000 0000 0000 0000 0000 0000 0000 0000
private const int SignalledState_ShiftCount = 31;
//1-bit for disposed state
private const int Dispose_BitMask = unchecked((int)0x40000000);//0100 0000 0000 0000 0000 0000 0000 0000
//11-bits for m_spinCount
private const int SpinCountState_BitMask = unchecked((int)0x3FF80000); //0011 1111 1111 1000 0000 0000 0000 0000
private const int SpinCountState_ShiftCount = 19;
private const int SpinCountState_MaxValue = (1 << 11) - 1; //2047
//19-bits for m_waiters. This allows support of 512K threads waiting which should be ample
private const int NumWaitersState_BitMask = unchecked((int)0x0007FFFF); // 0000 0000 0000 0111 1111 1111 1111 1111
private const int NumWaitersState_ShiftCount = 0;
private const int NumWaitersState_MaxValue = (1 << 19) - 1; //512K-1
// ----------- //
#if DEBUG
private static int s_nextId; // The next id that will be given out.
private int m_id = Interlocked.Increment(ref s_nextId); // A unique id for debugging purposes only.
private long m_lastSetTime;
private long m_lastResetTime;
#endif
/// <summary>
/// Gets the underlying <see cref="T:System.Threading.WaitHandle"/> object for this <see
/// cref="ManualResetEventSlim"/>.
/// </summary>
/// <value>The underlying <see cref="T:System.Threading.WaitHandle"/> event object fore this <see
/// cref="ManualResetEventSlim"/>.</value>
/// <remarks>
/// Accessing this property forces initialization of an underlying event object if one hasn't
/// already been created. To simply wait on this <see cref="ManualResetEventSlim"/>,
/// the public Wait methods should be preferred.
/// </remarks>
public WaitHandle WaitHandle
{
get
{
ThrowIfDisposed();
if (m_eventObj == null)
{
// Lazily initialize the event object if needed.
LazyInitializeEvent();
}
return m_eventObj;
}
}
/// <summary>
/// Gets whether the event is set.
/// </summary>
/// <value>true if the event has is set; otherwise, false.</value>
public bool IsSet
{
get
{
return 0 != ExtractStatePortion(m_combinedState, SignalledState_BitMask);
}
private set
{
UpdateStateAtomically(((value) ? 1 : 0) << SignalledState_ShiftCount, SignalledState_BitMask);
}
}
/// <summary>
/// Gets the number of spin waits that will be occur before falling back to a true wait.
/// </summary>
public int SpinCount
{
get
{
return ExtractStatePortionAndShiftRight(m_combinedState, SpinCountState_BitMask, SpinCountState_ShiftCount);
}
private set
{
Contract.Assert(value >= 0, "SpinCount is a restricted-width integer. The value supplied is outside the legal range.");
Contract.Assert(value <= SpinCountState_MaxValue, "SpinCount is a restricted-width integer. The value supplied is outside the legal range.");
// Don't worry about thread safety because it's set one time from the constructor
m_combinedState = (m_combinedState & ~SpinCountState_BitMask) | (value << SpinCountState_ShiftCount);
}
}
/// <summary>
/// How many threads are waiting.
/// </summary>
private int Waiters
{
get
{
return ExtractStatePortionAndShiftRight(m_combinedState, NumWaitersState_BitMask, NumWaitersState_ShiftCount);
}
set
{
//setting to <0 would indicate an internal flaw, hence Assert is appropriate.
Contract.Assert(value >= 0, "NumWaiters should never be less than zero. This indicates an internal error.");
// it is possible for the max number of waiters to be exceeded via user-code, hence we use a real exception here.
if (value >= NumWaitersState_MaxValue)
throw new InvalidOperationException(String.Format(Environment.GetResourceString("ManualResetEventSlim_ctor_TooManyWaiters"), NumWaitersState_MaxValue));
UpdateStateAtomically(value << NumWaitersState_ShiftCount, NumWaitersState_BitMask);
}
}
//-----------------------------------------------------------------------------------
// Constructs a new event, optionally specifying the initial state and spin count.
// The defaults are that the event is unsignaled and some reasonable default spin.
//
/// <summary>
/// Initializes a new instance of the <see cref="ManualResetEventSlim"/>
/// class with an initial state of nonsignaled.
/// </summary>
public ManualResetEventSlim()
: this(false)
{
}
/// <summary>
/// Initializes a new instance of the <see cref="ManualResetEventSlim"/>
/// class with a Boolen value indicating whether to set the intial state to signaled.
/// </summary>
/// <param name="initialState">true to set the initial state signaled; false to set the initial state
/// to nonsignaled.</param>
public ManualResetEventSlim(bool initialState)
{
// Specify the defualt spin count, and use default spin if we're
// on a multi-processor machine. Otherwise, we won't.
Initialize(initialState, DEFAULT_SPIN_MP);
}
/// <summary>
/// Initializes a new instance of the <see cref="ManualResetEventSlim"/>
/// class with a Boolen value indicating whether to set the intial state to signaled and a specified
/// spin count.
/// </summary>
/// <param name="initialState">true to set the initial state to signaled; false to set the initial state
/// to nonsignaled.</param>
/// <param name="spinCount">The number of spin waits that will occur before falling back to a true
/// wait.</param>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="spinCount"/> is less than
/// 0 or greater than the maximum allowed value.</exception>
public ManualResetEventSlim(bool initialState, int spinCount)
{
if (spinCount < 0)
{
throw new ArgumentOutOfRangeException("spinCount");
}
if (spinCount > SpinCountState_MaxValue)
{
throw new ArgumentOutOfRangeException(
"spinCount",
String.Format(Environment.GetResourceString("ManualResetEventSlim_ctor_SpinCountOutOfRange"), SpinCountState_MaxValue));
}
// We will suppress default spin because the user specified a count.
Initialize(initialState, spinCount);
}
/// <summary>
/// Initializes the internal state of the event.
/// </summary>
/// <param name="initialState">Whether the event is set initially or not.</param>
/// <param name="spinCount">The spin count that decides when the event will block.</param>
private void Initialize(bool initialState, int spinCount)
{
this.m_combinedState = initialState ? (1 << SignalledState_ShiftCount) : 0;
//the spinCount argument has been validated by the ctors.
//but we now sanity check our predefined constants.
Contract.Assert(DEFAULT_SPIN_SP >= 0, "Internal error - DEFAULT_SPIN_SP is outside the legal range.");
Contract.Assert(DEFAULT_SPIN_SP <= SpinCountState_MaxValue, "Internal error - DEFAULT_SPIN_SP is outside the legal range.");
SpinCount = PlatformHelper.IsSingleProcessor ? DEFAULT_SPIN_SP : spinCount;
}
/// <summary>
/// Helper to ensure the lock object is created before first use.
/// </summary>
private void EnsureLockObjectCreated()
{
Contract.Ensures(m_lock != null);
if (m_lock != null)
return;
object newObj = new object();
Interlocked.CompareExchange(ref m_lock, newObj, null); // failure is benign.. someone else won the ----.
}
/// <summary>
/// This method lazily initializes the event object. It uses CAS to guarantee that
/// many threads racing to call this at once don't result in more than one event
/// being stored and used. The event will be signaled or unsignaled depending on
/// the state of the thin-event itself, with synchronization taken into account.
/// </summary>
/// <returns>True if a new event was created and stored, false otherwise.</returns>
private bool LazyInitializeEvent()
{
bool preInitializeIsSet = IsSet;
ManualResetEvent newEventObj = new ManualResetEvent(preInitializeIsSet);
// We have to CAS this in case we are racing with another thread. We must
// guarantee only one event is actually stored in this field.
if (Interlocked.CompareExchange(ref m_eventObj, newEventObj, null) != null)
{
// We raced with someone else and lost. Destroy the garbage event.
newEventObj.Close();
return false;
}
else
{
// Now that the event is published, verify that the state hasn't changed since
// we snapped the preInitializeState. Another thread could have done that
// between our initial observation above and here. The barrier incurred from
// the CAS above (in addition to m_state being volatile) prevents this read
// from moving earlier and being collapsed with our original one.
bool currentIsSet = IsSet;
if (currentIsSet != preInitializeIsSet)
{
Contract.Assert(currentIsSet,
"The only safe concurrent transition is from unset->set: detected set->unset.");
// We saw it as unsignaled, but it has since become set.
lock (newEventObj)
{
// If our event hasn't already been disposed of, we must set it.
if (m_eventObj == newEventObj)
{
newEventObj.Set();
}
}
}
return true;
}
}
/// <summary>
/// Sets the state of the event to signaled, which allows one or more threads waiting on the event to
/// proceed.
/// </summary>
public void Set()
{
Set(false);
}
/// <summary>
/// Private helper to actually perform the Set.
/// </summary>
/// <param name="duringCancellation">Indicates whether we are calling Set() during cancellation.</param>
/// <exception cref="T:System.OperationCanceledException">The object has been canceled.</exception>
private void Set(bool duringCancellation)
{
// We need to ensure that IsSet=true does not get reordered past the read of m_eventObj
// This would be a legal movement according to the .NET memory model.
// The code is safe as IsSet involves an Interlocked.CompareExchange which provides a full memory barrier.
IsSet = true;
// If there are waiting threads, we need to pulse them.
if (Waiters > 0)
{
Contract.Assert(m_lock != null); //if waiters>0, then m_lock has already been created.
lock (m_lock)
{
Monitor.PulseAll(m_lock);
}
}
ManualResetEvent eventObj = m_eventObj;
//Design-decision: do not set the event if we are in cancellation -> better to deadlock than to wake up waiters incorrectly
//It would be preferable to wake up the event and have it throw OCE. This requires MRE to implement cancellation logic
if (eventObj != null && !duringCancellation)
{
// We must surround this call to Set in a lock. The reason is fairly subtle.
// Sometimes a thread will issue a Wait and wake up after we have set m_state,
// but before we have gotten around to setting m_eventObj (just below). That's
// because Wait first checks m_state and will only access the event if absolutely
// necessary. However, the coding pattern { event.Wait(); event.Dispose() } is
// quite common, and we must support it. If the waiter woke up and disposed of
// the event object before the setter has finished, however, we would try to set a
// now-disposed Win32 event. Crash! To deal with this ----, we use a lock to
// protect access to the event object when setting and disposing of it. We also
// double-check that the event has not become null in the meantime when in the lock.
lock (eventObj)
{
if (m_eventObj != null)
{
// If somebody is waiting, we must set the event.
m_eventObj.Set();
}
}
}
#if DEBUG
m_lastSetTime = DateTime.Now.Ticks;
#endif
}
/// <summary>
/// Sets the state of the event to nonsignaled, which causes threads to block.
/// </summary>
/// <remarks>
/// Unlike most of the members of <see cref="ManualResetEventSlim"/>, <see cref="Reset()"/> is not
/// thread-safe and may not be used concurrently with other members of this instance.
/// </remarks>
public void Reset()
{
ThrowIfDisposed();
// If there's an event, reset it.
if (m_eventObj != null)
{
m_eventObj.Reset();
}
// There is a ---- here. If another thread Sets the event, we will get into a state
// where m_state will be unsignaled, yet the Win32 event object will have been signaled.
// This could cause waiting threads to wake up even though the event is in an
// unsignaled state. This is fine -- those that are calling Reset concurrently are
// responsible for doing "the right thing" -- e.g. rechecking the condition and
// resetting the event manually.
// And finally set our state back to unsignaled.
IsSet = false;
#if DEBUG
m_lastResetTime = DateTime.Now.Ticks;
#endif
}
/// <summary>
/// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set.
/// </summary>
/// <exception cref="T:System.InvalidOperationException">
/// The maximum number of waiters has been exceeded.
/// </exception>
/// <remarks>
/// The caller of this method blocks indefinitely until the current instance is set. The caller will
/// return immediately if the event is currently in a set state.
/// </remarks>
public void Wait()
{
Wait(Timeout.Infinite, new CancellationToken());
}
/// <summary>
/// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> receives a signal,
/// while observing a <see cref="T:System.Threading.CancellationToken"/>.
/// </summary>
/// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
/// observe.</param>
/// <exception cref="T:System.InvalidOperationException">
/// The maximum number of waiters has been exceeded.
/// </exception>
/// <exception cref="T:System.OperationCanceledExcepton"><paramref name="cancellationToken"/> was
/// canceled.</exception>
/// <remarks>
/// The caller of this method blocks indefinitely until the current instance is set. The caller will
/// return immediately if the event is currently in a set state.
/// </remarks>
public void Wait(CancellationToken cancellationToken)
{
Wait(Timeout.Infinite, cancellationToken);
}
/// <summary>
/// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
/// <see cref="T:System.TimeSpan"/> to measure the time interval.
/// </summary>
/// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
/// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
/// </param>
/// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
/// false.</returns>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
/// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
/// than <see cref="System.Int32.MaxValue"/>.</exception>
/// <exception cref="T:System.InvalidOperationException">
/// The maximum number of waiters has been exceeded.
/// </exception>
public bool Wait(TimeSpan timeout)
{
long totalMilliseconds = (long)timeout.TotalMilliseconds;
if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
{
throw new ArgumentOutOfRangeException("timeout");
}
return Wait((int)totalMilliseconds, new CancellationToken());
}
/// <summary>
/// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
/// <see cref="T:System.TimeSpan"/> to measure the time interval, while observing a <see
/// cref="T:System.Threading.CancellationToken"/>.
/// </summary>
/// <param name="timeout">A <see cref="System.TimeSpan"/> that represents the number of milliseconds
/// to wait, or a <see cref="System.TimeSpan"/> that represents -1 milliseconds to wait indefinitely.
/// </param>
/// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
/// observe.</param>
/// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
/// false.</returns>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="timeout"/> is a negative
/// number other than -1 milliseconds, which represents an infinite time-out -or- timeout is greater
/// than <see cref="System.Int32.MaxValue"/>.</exception>
/// <exception cref="T:System.Threading.OperationCanceledException"><paramref
/// name="cancellationToken"/> was canceled.</exception>
/// <exception cref="T:System.InvalidOperationException">
/// The maximum number of waiters has been exceeded.
/// </exception>
public bool Wait(TimeSpan timeout, CancellationToken cancellationToken)
{
long totalMilliseconds = (long)timeout.TotalMilliseconds;
if (totalMilliseconds < -1 || totalMilliseconds > int.MaxValue)
{
throw new ArgumentOutOfRangeException("timeout");
}
return Wait((int)totalMilliseconds, cancellationToken);
}
/// <summary>
/// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
/// 32-bit signed integer to measure the time interval.
/// </summary>
/// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
/// cref="Timeout.Infinite"/>(-1) to wait indefinitely.</param>
/// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
/// false.</returns>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a
/// negative number other than -1, which represents an infinite time-out.</exception>
/// <exception cref="T:System.InvalidOperationException">
/// The maximum number of waiters has been exceeded.
/// </exception>
public bool Wait(int millisecondsTimeout)
{
return Wait(millisecondsTimeout, new CancellationToken());
}
/// <summary>
/// Blocks the current thread until the current <see cref="ManualResetEventSlim"/> is set, using a
/// 32-bit signed integer to measure the time interval, while observing a <see
/// cref="T:System.Threading.CancellationToken"/>.
/// </summary>
/// <param name="millisecondsTimeout">The number of milliseconds to wait, or <see
/// cref="Timeout.Infinite"/>(-1) to wait indefinitely.</param>
/// <param name="cancellationToken">The <see cref="T:System.Threading.CancellationToken"/> to
/// observe.</param>
/// <returns>true if the <see cref="System.Threading.ManualResetEventSlim"/> was set; otherwise,
/// false.</returns>
/// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="millisecondsTimeout"/> is a
/// negative number other than -1, which represents an infinite time-out.</exception>
/// <exception cref="T:System.InvalidOperationException">
/// The maximum number of waiters has been exceeded.
/// </exception>
/// <exception cref="T:System.Threading.OperationCanceledException"><paramref
/// name="cancellationToken"/> was canceled.</exception>
public bool Wait(int millisecondsTimeout, CancellationToken cancellationToken)
{
ThrowIfDisposed();
cancellationToken.ThrowIfCancellationRequested(); // an early convenience check
if (millisecondsTimeout < -1)
{
throw new ArgumentOutOfRangeException("millisecondsTimeout");
}
if (!IsSet)
{
if (millisecondsTimeout == 0)
{
// For 0-timeouts, we just return immediately.
return false;
}
// We spin briefly before falling back to allocating and/or waiting on a true event.
uint startTime = 0;
bool bNeedTimeoutAdjustment = false;
int realMillisecondsTimeout = millisecondsTimeout; //this will be adjusted if necessary.
if (millisecondsTimeout != Timeout.Infinite)
{
// We will account for time spent spinning, so that we can decrement it from our
// timeout. In most cases the time spent in this section will be negligible. But
// we can't discount the possibility of our thread being switched out for a lengthy
// period of time. The timeout adjustments only take effect when and if we actually
// decide to block in the kernel below.
startTime = TimeoutHelper.GetTime();
bNeedTimeoutAdjustment = true;
}
//spin
int HOW_MANY_SPIN_BEFORE_YIELD = 10;
int HOW_MANY_YIELD_EVERY_SLEEP_0 = 5;
int HOW_MANY_YIELD_EVERY_SLEEP_1 = 20;
int spinCount = SpinCount;
for (int i = 0; i < spinCount; i++)
{
if (IsSet)
{
return true;
}
else if (i < HOW_MANY_SPIN_BEFORE_YIELD)
{
if (i == HOW_MANY_SPIN_BEFORE_YIELD / 2)
{
#if PFX_LEGACY_3_5
Platform.Yield();
#else
Thread.Yield();
#endif
}
else
{
Thread.SpinWait(4 << i);
}
}
else if (i % HOW_MANY_YIELD_EVERY_SLEEP_1 == 0)
{
Thread.Sleep(1);
}
else if (i % HOW_MANY_YIELD_EVERY_SLEEP_0 == 0)
{
Thread.Sleep(0);
}
else
{
#if PFX_LEGACY_3_5
Platform.Yield();
#else
Thread.Yield();
#endif
}
if (i >= 100 && i % 10 == 0) // check the cancellation token if the user passed a very large spin count
cancellationToken.ThrowIfCancellationRequested();
}
// Now enter the lock and wait.
EnsureLockObjectCreated();
// We must register and deregister the token outside of the lock, to avoid deadlocks.
using (cancellationToken.InternalRegisterWithoutEC(s_cancellationTokenCallback, this))
{
lock (m_lock)
{
// Loop to cope with spurious wakeups from other waits being canceled
while (!IsSet)
{
// If our token was canceled, we must throw and exit.
cancellationToken.ThrowIfCancellationRequested();
//update timeout (delays in wait commencement are due to spinning and/or spurious wakeups from other waits being canceled)
if (bNeedTimeoutAdjustment)
{
realMillisecondsTimeout = TimeoutHelper.UpdateTimeOut(startTime, millisecondsTimeout);
if (realMillisecondsTimeout <= 0)
return false;
}
// There is a ---- that Set will fail to see that there are waiters as Set does not take the lock,
// so after updating waiters, we must check IsSet again.
// Also, we must ensure there cannot be any reordering of the assignment to Waiters and the
// read from IsSet. This is guaranteed as Waiters{set;} involves an Interlocked.CompareExchange
// operation which provides a full memory barrier.
// If we see IsSet=false, then we are guaranteed that Set() will see that we are
// waiting and will pulse the monitor correctly.
Waiters = Waiters + 1;
if (IsSet) //This check must occur after updating Waiters.
{
Waiters--; //revert the increment.
return true;
}
// Now finally perform the wait.
try
{
// ** the actual wait **
if (!Monitor.Wait(m_lock, realMillisecondsTimeout))
return false; //return immediately if the timeout has expired.
}
finally
{
// Clean up: we're done waiting.
Waiters = Waiters - 1;
}
// Now just loop back around, and the right thing will happen. Either:
// 1. We had a spurious wake-up due to some other wait being canceled via a different cancellationToken (rewait)
// or 2. the wait was successful. (the loop will break)
}
}
}
} // automatically disposes (and deregisters) the callback
return true; //done. The wait was satisfied.
}
/// <summary>
/// Releases all resources used by the current instance of <see cref="ManualResetEventSlim"/>.
/// </summary>
/// <remarks>
/// Unlike most of the members of <see cref="ManualResetEventSlim"/>, <see cref="Dispose()"/> is not
/// thread-safe and may not be used concurrently with other members of this instance.
/// </remarks>
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
/// <summary>
/// When overridden in a derived class, releases the unmanaged resources used by the
/// <see cref="ManualResetEventSlim"/>, and optionally releases the managed resources.
/// </summary>
/// <param name="disposing">true to release both managed and unmanaged resources;
/// false to release only unmanaged resources.</param>
/// <remarks>
/// Unlike most of the members of <see cref="ManualResetEventSlim"/>, <see cref="Dispose(Boolean)"/> is not
/// thread-safe and may not be used concurrently with other members of this instance.
/// </remarks>
protected virtual void Dispose(bool disposing)
{
if ((m_combinedState & Dispose_BitMask) != 0)
return; // already disposed
m_combinedState |= Dispose_BitMask; //set the dispose bit
if (disposing)
{
// We will dispose of the event object. We do this under a lock to protect
// against the race condition outlined in the Set method above.
ManualResetEvent eventObj = m_eventObj;
if (eventObj != null)
{
lock (eventObj)
{
eventObj.Close();
m_eventObj = null;
}
}
}
}
/// <summary>
/// Throw ObjectDisposedException if the MRES is disposed
/// </summary>
private void ThrowIfDisposed()
{
if ((m_combinedState & Dispose_BitMask) != 0)
throw new ObjectDisposedException(Environment.GetResourceString("ManualResetEventSlim_Disposed"));
}
/// <summary>
/// Private helper method to wake up waiters when a cancellationToken gets canceled.
/// </summary>
private static Action<object> s_cancellationTokenCallback = new Action<object>(CancellationTokenCallback);
private static void CancellationTokenCallback(object obj)
{
ManualResetEventSlim mre = obj as ManualResetEventSlim;
Contract.Assert(mre != null, "Expected a ManualResetEventSlim");
Contract.Assert(mre.m_lock != null); //the lock should have been created before this callback is registered for use.
lock (mre.m_lock)
{
Monitor.PulseAll(mre.m_lock); // awaken all waiters
}
}
/// <summary>
/// Private helper method for updating parts of a bit-string state value.
/// Mainly called from the IsSet and Waiters properties setters
/// </summary>
/// <remarks>
/// Note: the parameter types must be int as CompareExchange cannot take a Uint
/// </remarks>
/// <param name="newBits">The new value</param>
/// <param name="updateBitsMask">The mask used to set the bits</param>
private void UpdateStateAtomically(int newBits, int updateBitsMask)
{
SpinWait sw = new SpinWait();
Contract.Assert((newBits | updateBitsMask) == updateBitsMask, "newBits do not fall within the updateBitsMask.");
do
{
int oldState = m_combinedState; // cache the old value for testing in CAS
// Procedure:(1) zero the updateBits. eg oldState = [11111111] flag= [00111000] newState = [11000111]
// then (2) map in the newBits. eg [11000111] newBits=00101000, newState=[11101111]
int newState = (oldState & ~updateBitsMask) | newBits;
if (Interlocked.CompareExchange(ref m_combinedState, newState, oldState) == oldState)
{
return;
}
sw.SpinOnce();
} while (true);
}
/// <summary>
/// Private helper method - performs Mask and shift, particular helpful to extract a field from a packed word.
/// eg ExtractStatePortionAndShiftRight(0x12345678, 0xFF000000, 24) => 0x12, ie extracting the top 8-bits as a simple integer
///
/// ?? is there a common place to put this rather than being private to MRES?
/// </summary>
/// <param name="state"></param>
/// <param name="mask"></param>
/// <param name="rightBitShiftCount"></param>
/// <returns></returns>
private static int ExtractStatePortionAndShiftRight(int state, int mask, int rightBitShiftCount)
{
//convert to uint before shifting so that right-shift does not replicate the sign-bit,
//then convert back to int.
return unchecked((int)(((uint)(state & mask)) >> rightBitShiftCount));
}
/// <summary>
/// Performs a Mask operation, but does not perform the shift.
/// This is acceptable for boolean values for which the shift is unnecessary
/// eg (val & Mask) != 0 is an appropriate way to extract a boolean rather than using
/// ((val & Mask) >> shiftAmount) == 1
///
/// ?? is there a common place to put this rather than being private to MRES?
/// </summary>
/// <param name="state"></param>
/// <param name="mask"></param>
private static int ExtractStatePortion(int state, int mask)
{
return state & mask;
}
}
}
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