80 lines
3.4 KiB
C#
80 lines
3.4 KiB
C#
/*
|
|
* Copyright (c) 2024, Sjofn LLC
|
|
* All rights reserved.
|
|
*
|
|
* - Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions are met:
|
|
*
|
|
* - Redistributions of source code must retain the above copyright notice, this
|
|
* list of conditions and the following disclaimer.
|
|
* - Neither the name of the openmetaverse.co nor the names
|
|
* of its contributors may be used to endorse or promote products derived from
|
|
* this software without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
|
|
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
using System.Threading;
|
|
|
|
namespace LibreMetaverse.Threading
|
|
{
|
|
/// <summary>
|
|
/// A real slim SpinWait (the Microsoft version is slower than the normal use of
|
|
/// the lock keyword for uncontended locks).
|
|
/// This lock never verifies ownership, so it will dead-lock if you try
|
|
/// to enter it twice and it will allow one thread to enter the lock and
|
|
/// another thread to release it (if you want that, it will be great... if not,
|
|
/// you will be causing bugs).
|
|
/// It should only be used in situations where the lock is expected to be
|
|
/// held for very short times and when performance is really critical.
|
|
/// This is a struct, so if you for some reason need to pass it as a parameter,
|
|
/// use it as a ref, or else you will end-up using a copy of the lock instead
|
|
/// of working on the real one.
|
|
/// </summary>
|
|
public struct SpinLockSlim
|
|
{
|
|
private int _locked;
|
|
|
|
/// <summary>
|
|
/// Enters the lock. So you can do your actions in a safe manner.
|
|
/// </summary>
|
|
public void Enter()
|
|
{
|
|
if (Interlocked.CompareExchange(ref _locked, 1, 0) == 0)
|
|
return;
|
|
|
|
SpinWait spinWait = new SpinWait();
|
|
while(true)
|
|
{
|
|
spinWait.SpinOnce();
|
|
|
|
if (Interlocked.CompareExchange(ref _locked, 1, 0) == 0)
|
|
return;
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Exits the lock. If the same thread exits and enters the lock constantly, it will
|
|
/// probably got the lock many times before letting other threads get it, even if those
|
|
/// other threads started to wait before the actual thread releases the lock. Fairness
|
|
/// is not a strong point of this lock.
|
|
/// </summary>
|
|
public void Exit()
|
|
{
|
|
// There is no need to use a "volatile" write as all .NET writes
|
|
// have "release" semantics.
|
|
_locked = 0;
|
|
}
|
|
}
|
|
}
|