Ryujinx/Ryujinx.Common/Memory/PartialUnmaps/NativeReaderWriterLock.cs
riperiperi 14ce9e1567
Move partial unmap handler to the native signal handler (#3437)
* Initial commit with a lot of testing stuff.

* Partial Unmap Cleanup Part 1

* Fix some minor issues, hopefully windows tests.

* Disable partial unmap tests on macos for now

Weird issue.

* Goodbye magic number

* Add COMPlus_EnableAlternateStackCheck for tests

`COMPlus_EnableAlternateStackCheck` is needed for NullReferenceException handling to work on linux after registering the signal handler, due to how dotnet registers its own signal handler.

* Address some feedback

* Force retry when memory is mapped in memory tracking

This case existed before, but returning `false` no longer retries, so it would crash immediately after unprotecting the memory... Now, we return `true` to deliberately retry.

This case existed before (was just broken by this change) and I don't really want to look into fixing the issue right now. Technically, this means that on guest code partial unmaps will retry _due to this_ rather than hitting the handler. I don't expect this to cause any issues.

This should fix random crashes in Xenoblade Chronicles 2.

* Use IsRangeMapped

* Suppress MockMemoryManager.UnmapEvent warning

This event is not signalled by the mock memory manager.

* Remove 4kb mapping
2022-07-29 19:16:29 -03:00

80 lines
2.5 KiB
C#

using System.Runtime.InteropServices;
using System.Threading;
using static Ryujinx.Common.Memory.PartialUnmaps.PartialUnmapHelpers;
namespace Ryujinx.Common.Memory.PartialUnmaps
{
/// <summary>
/// A simple implementation of a ReaderWriterLock which can be used from native code.
/// </summary>
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct NativeReaderWriterLock
{
public int WriteLock;
public int ReaderCount;
public static int WriteLockOffset;
public static int ReaderCountOffset;
/// <summary>
/// Populates the field offsets for use when emitting native code.
/// </summary>
static NativeReaderWriterLock()
{
NativeReaderWriterLock instance = new NativeReaderWriterLock();
WriteLockOffset = OffsetOf(ref instance, ref instance.WriteLock);
ReaderCountOffset = OffsetOf(ref instance, ref instance.ReaderCount);
}
/// <summary>
/// Acquires the reader lock.
/// </summary>
public void AcquireReaderLock()
{
// Must take write lock for a very short time to become a reader.
while (Interlocked.CompareExchange(ref WriteLock, 1, 0) != 0) { }
Interlocked.Increment(ref ReaderCount);
Interlocked.Exchange(ref WriteLock, 0);
}
/// <summary>
/// Releases the reader lock.
/// </summary>
public void ReleaseReaderLock()
{
Interlocked.Decrement(ref ReaderCount);
}
/// <summary>
/// Upgrades to a writer lock. The reader lock is temporarily released while obtaining the writer lock.
/// </summary>
public void UpgradeToWriterLock()
{
// Prevent any more threads from entering reader.
// If the write lock is already taken, wait for it to not be taken.
Interlocked.Decrement(ref ReaderCount);
while (Interlocked.CompareExchange(ref WriteLock, 1, 0) != 0) { }
// Wait for reader count to drop to 0, then take the lock again as the only reader.
while (Interlocked.CompareExchange(ref ReaderCount, 1, 0) != 0) { }
}
/// <summary>
/// Downgrades from a writer lock, back to a reader one.
/// </summary>
public void DowngradeFromWriterLock()
{
// Release the WriteLock.
Interlocked.Exchange(ref WriteLock, 0);
}
}
}