diff options
Diffstat (limited to 'src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs')
| -rw-r--r-- | src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs | 51 |
1 files changed, 45 insertions, 6 deletions
diff --git a/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs b/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs index 414ad1852..54857c322 100644 --- a/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs +++ b/src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs @@ -88,7 +88,16 @@ namespace System.Threading /// for here. /// </remarks> internal static readonly int SpinCountforSpinBeforeWait = PlatformHelper.IsSingleProcessor ? 1 : 35; - internal const int Sleep1ThresholdForSpinBeforeWait = 40; // should be greater than SpinCountforSpinBeforeWait + + /// <summary> + /// Typically, Sleep(1) should not be issued for a spin-wait before a proper wait because it is usually more beneficial + /// to just issue the proper wait. For longer spin-waits (when the spin count is configurable), this value may be used as + /// a threshold for issuing Sleep(1). + /// </summary> + /// <remarks> + /// Should be greater than <see cref="SpinCountforSpinBeforeWait"/> so that Sleep(1) would not be used by default. + /// </remarks> + internal const int Sleep1ThresholdForLongSpinBeforeWait = 40; // The number of times we've spun already. private int _count; @@ -127,12 +136,42 @@ namespace System.Threading /// </remarks> public void SpinOnce() { - SpinOnce(DefaultSleep1Threshold); + SpinOnceCore(DefaultSleep1Threshold); + } + + /// <summary> + /// Performs a single spin. + /// </summary> + /// <param name="sleep1Threshold"> + /// A minimum spin count after which <code>Thread.Sleep(1)</code> may be used. A value of <code>-1</code> may be used to + /// disable the use of <code>Thread.Sleep(1)</code>. + /// </param> + /// <exception cref="ArgumentOutOfRangeException"> + /// <paramref name="sleep1Threshold"/> is less than <code>-1</code>. + /// </exception> + /// <remarks> + /// This is typically called in a loop, and may change in behavior based on the number of times a + /// <see cref="SpinOnce"/> has been called thus far on this instance. + /// </remarks> + public void SpinOnce(int sleep1Threshold) + { + if (sleep1Threshold < -1) + { + throw new ArgumentOutOfRangeException(nameof(sleep1Threshold), sleep1Threshold, SR.ArgumentOutOfRange_NeedNonNegOrNegative1); + } + + if (sleep1Threshold >= 0 && sleep1Threshold < YieldThreshold) + { + sleep1Threshold = YieldThreshold; + } + + SpinOnceCore(sleep1Threshold); } - internal void SpinOnce(int sleep1Threshold) + private void SpinOnceCore(int sleep1Threshold) { - Debug.Assert(sleep1Threshold >= YieldThreshold || PlatformHelper.IsSingleProcessor); // so that NextSpinWillYield behaves as requested + Debug.Assert(sleep1Threshold >= -1); + Debug.Assert(sleep1Threshold < 0 || sleep1Threshold >= YieldThreshold); // (_count - YieldThreshold) % 2 == 0: The purpose of this check is to interleave Thread.Yield/Sleep(0) with // Thread.SpinWait. Otherwise, the following issues occur: @@ -145,7 +184,7 @@ namespace System.Threading // contention), they may switch between one another, delaying work that can make progress. if (( _count >= YieldThreshold && - (_count >= sleep1Threshold || (_count - YieldThreshold) % 2 == 0) + ((_count >= sleep1Threshold && sleep1Threshold >= 0) || (_count - YieldThreshold) % 2 == 0) ) || PlatformHelper.IsSingleProcessor) { @@ -164,7 +203,7 @@ namespace System.Threading // configured to use the (default) coarse-grained system timer. // - if (_count >= sleep1Threshold) + if (_count >= sleep1Threshold && sleep1Threshold >= 0) { RuntimeThread.Sleep(1); } |