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using System.Threading;
namespace Pathfinding.Jobs {
/// <summary>
/// Spin lock which can be used in Burst.
/// Good when the lock is generally uncontested.
/// Very inefficient when the lock is contested.
/// </summary>
public struct SpinLock {
private volatile int locked;
public void Lock () {
while (Interlocked.CompareExchange(ref locked, 1, 0) != 0)
Unity.Burst.Intrinsics.Common.Pause(); // spin
// We need to ensure that any optimizer does not reorder loads to before we aquire the lock.
System.Threading.Thread.MemoryBarrier();
}
public void Unlock () {
// We need a memory barrier to ensure that all writes are visible to other threads, before we unlock.
// We also need to ensure that any optimizer does not reorder stores to after the unlock.
System.Threading.Thread.MemoryBarrier();
// Release the lock by writing 0 to it. Use atomics to make it immediately visible to other threads.
if (Interlocked.Exchange(ref locked, 0) == 0) throw new System.InvalidOperationException("Trying to unlock a lock which is not locked");
}
}
}
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