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[NativeAOT] Thin locks (dotnet#79519)
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* switch to managed thread ID in Lock

* fattening the lock

* __declspec(selectany)

* few tweaks

* fairness

* more room for thread ids

* remove CurrentNativeThreadId

* couple fixes

* fix win-arm64 build

* win-arm64 build , another try

* Apply suggestions from code review

Co-authored-by: Jan Kotas <[email protected]>

* fix after renaming

* do not report successful spin if thread has waited

* keep extern and undo mangling of tls_CurrentThread in asm

* use SyncTable indexer in less perf-sensitive places.

* GetNewHashCode just delegate to shared random

* Apply suggestions from code review

Co-authored-by: Jan Kotas <[email protected]>

* unchecked const conversion

* some refactoring comments and typos

* min number of spins in the backoff

* moved CurrentManagedThreadIdUnchecked to ManagedThreadId

* Use `-1` to report success and allow using  element #1 in the SyncTable

* use threadstatic for managed thread ID

* check before calling RhGetProcessCpuCount

* use 0 as default thread ID

Co-authored-by: Jan Kotas <[email protected]>
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VSadov and jkotas authored Dec 15, 2022
1 parent ca873ea commit d7924cc
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Showing 16 changed files with 744 additions and 306 deletions.
4 changes: 2 additions & 2 deletions src/coreclr/nativeaot/Runtime/MiscHelpers.cpp
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Expand Up @@ -51,11 +51,11 @@ EXTERN_C NATIVEAOT_API void __cdecl RhSpinWait(int32_t iterations)
ASSERT(iterations > 0);

// limit the spin count in coop mode.
ASSERT_MSG(iterations <= 10000 || !ThreadStore::GetCurrentThread()->IsCurrentThreadInCooperativeMode(),
ASSERT_MSG(iterations <= 1024 || !ThreadStore::GetCurrentThread()->IsCurrentThreadInCooperativeMode(),
"This is too long wait for coop mode. You must p/invoke with GC transition.");

YieldProcessorNormalizationInfo normalizationInfo;
YieldProcessorNormalizedForPreSkylakeCount(normalizationInfo, iterations);
YieldProcessorNormalized(normalizationInfo, iterations);
}

// Yield the cpu to another thread ready to process, if one is available.
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7 changes: 5 additions & 2 deletions src/coreclr/nativeaot/Runtime/thread.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -260,7 +260,10 @@ void Thread::Construct()
// alloc_context ever needs different initialization, a matching change to the tls_CurrentThread
// static initialization will need to be made.

m_uPalThreadIdForLogging = PalGetCurrentThreadIdForLogging();
m_pTransitionFrame = TOP_OF_STACK_MARKER;
m_pDeferredTransitionFrame = TOP_OF_STACK_MARKER;
m_hPalThread = INVALID_HANDLE_VALUE;

m_threadId.SetToCurrentThread();

HANDLE curProcessPseudo = PalGetCurrentProcess();
Expand Down Expand Up @@ -328,7 +331,7 @@ bool Thread::CatchAtSafePoint()

uint64_t Thread::GetPalThreadIdForLogging()
{
return m_uPalThreadIdForLogging;
return *(uint64_t*)&m_threadId;
}

bool Thread::IsCurrentThread()
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5 changes: 2 additions & 3 deletions src/coreclr/nativeaot/Runtime/thread.h
Original file line number Diff line number Diff line change
Expand Up @@ -95,8 +95,7 @@ struct ThreadBuffer
PTR_VOID m_pStackLow;
PTR_VOID m_pStackHigh;
PTR_UInt8 m_pTEB; // Pointer to OS TEB structure for this thread
uint64_t m_uPalThreadIdForLogging; // @TODO: likely debug-only
EEThreadId m_threadId;
EEThreadId m_threadId; // OS thread ID
PTR_VOID m_pThreadStressLog; // pointer to head of thread's StressLogChunks
NATIVE_CONTEXT* m_interruptedContext; // context for an asynchronously interrupted thread.
#ifdef FEATURE_SUSPEND_REDIRECTION
Expand Down Expand Up @@ -192,7 +191,7 @@ class Thread : private ThreadBuffer
gc_alloc_context * GetAllocContext(); // @TODO: I would prefer to not expose this in this way

#ifndef DACCESS_COMPILE
uint64_t GetPalThreadIdForLogging();
uint64_t GetPalThreadIdForLogging();
bool IsCurrentThread();

void GcScanRoots(void * pfnEnumCallback, void * pvCallbackData);
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17 changes: 3 additions & 14 deletions src/coreclr/nativeaot/Runtime/threadstore.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -415,20 +415,9 @@ COOP_PINVOKE_HELPER(void, RhpCancelThreadAbort, (void* thread))

C_ASSERT(sizeof(Thread) == sizeof(ThreadBuffer));

EXTERN_C DECLSPEC_THREAD ThreadBuffer tls_CurrentThread;
DECLSPEC_THREAD ThreadBuffer tls_CurrentThread =
{
{ 0 }, // m_rgbAllocContextBuffer
Thread::TSF_Unknown, // m_ThreadStateFlags
TOP_OF_STACK_MARKER, // m_pTransitionFrame
TOP_OF_STACK_MARKER, // m_pDeferredTransitionFrame
0, // m_pCachedTransitionFrame
0, // m_pNext
INVALID_HANDLE_VALUE, // m_hPalThread
0, // m_ppvHijackedReturnAddressLocation
0, // m_pvHijackedReturnAddress
0, // all other fields are initialized by zeroes
};
#ifndef _MSC_VER
__thread ThreadBuffer tls_CurrentThread;
#endif

EXTERN_C ThreadBuffer* RhpGetThread()
{
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7 changes: 6 additions & 1 deletion src/coreclr/nativeaot/Runtime/threadstore.inl
Original file line number Diff line number Diff line change
@@ -1,7 +1,12 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

EXTERN_C DECLSPEC_THREAD ThreadBuffer tls_CurrentThread;
#ifdef _MSC_VER
// a workaround to prevent tls_CurrentThread from becoming dynamically checked/initialized.
EXTERN_C __declspec(selectany) __declspec(thread) ThreadBuffer tls_CurrentThread;
#else
EXTERN_C __thread ThreadBuffer tls_CurrentThread;
#endif

// static
inline Thread * ThreadStore::RawGetCurrentThread()
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Expand Up @@ -14,42 +14,68 @@ internal static class SynchronizedMethodHelpers
private static void MonitorEnter(object obj, ref bool lockTaken)
{
// Inlined Monitor.Enter with a few tweaks
Lock lck = Monitor.GetLock(obj);
int resultOrIndex = ObjectHeader.Acquire(obj);
if (resultOrIndex < 0)
{
lockTaken = true;
return;
}

Lock lck = resultOrIndex == 0 ?
ObjectHeader.GetLockObject(obj) :
SyncTable.GetLockObject(resultOrIndex);

if (lck.TryAcquire(0))
{
lockTaken = true;
return;
}

Monitor.TryAcquireContended(lck, obj, Timeout.Infinite);
lockTaken = true;
}
private static void MonitorExit(object obj, ref bool lockTaken)
{
// Inlined Monitor.Exit with a few tweaks
if (!lockTaken) return;
Monitor.GetLock(obj).Release();
if (!lockTaken)
return;

ObjectHeader.Release(obj);
lockTaken = false;
}

private static void MonitorEnterStatic(IntPtr pEEType, ref bool lockTaken)
{
// Inlined Monitor.Enter with a few tweaks
object obj = GetStaticLockObject(pEEType);
Lock lck = Monitor.GetLock(obj);
int resultOrIndex = ObjectHeader.Acquire(obj);
if (resultOrIndex < 0)
{
lockTaken = true;
return;
}

Lock lck = resultOrIndex == 0 ?
ObjectHeader.GetLockObject(obj) :
SyncTable.GetLockObject(resultOrIndex);

if (lck.TryAcquire(0))
{
lockTaken = true;
return;
}

Monitor.TryAcquireContended(lck, obj, Timeout.Infinite);
lockTaken = true;
}
private static void MonitorExitStatic(IntPtr pEEType, ref bool lockTaken)
{
// Inlined Monitor.Exit with a few tweaks
if (!lockTaken) return;
if (!lockTaken)
return;

object obj = GetStaticLockObject(pEEType);
Monitor.GetLock(obj).Release();
ObjectHeader.Release(obj);
lockTaken = false;
}

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Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,6 @@ namespace System
{
public static partial class Environment
{
internal static int CurrentNativeThreadId => ManagedThreadId.Current;

public static long TickCount64 => (long)RuntimeImports.RhpGetTickCount64();

[DoesNotReturn]
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Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,6 @@ namespace System
{
public static partial class Environment
{
internal static int CurrentNativeThreadId => unchecked((int)Interop.Kernel32.GetCurrentThreadId());

public static long TickCount64 => (long)Interop.Kernel32.GetTickCount64();

[DoesNotReturn]
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Original file line number Diff line number Diff line change
Expand Up @@ -94,17 +94,9 @@ public static object GetObjectValue(object? obj)
return RuntimeImports.RhCompareObjectContentsAndPadding(o1, o2);
}

[ThreadStatic]
private static int t_hashSeed;

internal static int GetNewHashCode()
{
int multiplier = Environment.CurrentManagedThreadId * 4 + 5;
// Every thread has its own generator for hash codes so that we won't get into a situation
// where two threads consistently give out the same hash codes.
// Choice of multiplier guarantees period of 2**32 - see Knuth Vol 2 p16 (3.2.1.2 Theorem A).
t_hashSeed = t_hashSeed * multiplier + 1;
return t_hashSeed;
return Random.Shared.Next();
}

public static unsafe int GetHashCode(object o)
Expand Down Expand Up @@ -228,6 +220,9 @@ internal static unsafe ushort GetElementSize(this Array array)
internal static unsafe MethodTable* GetMethodTable(this object obj)
=> obj.m_pEEType;

internal static unsafe ref MethodTable* GetMethodTableRef(this object obj)
=> ref obj.m_pEEType;

internal static unsafe EETypePtr GetEETypePtr(this object obj)
=> new EETypePtr(obj.m_pEEType);

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Original file line number Diff line number Diff line change
Expand Up @@ -464,7 +464,7 @@ private static void SerializeExceptionsForDump(Exception currentException, IntPt
LowLevelList<Exception> exceptions = new LowLevelList<Exception>(curThreadExceptions);
LowLevelList<Exception> nonThrownInnerExceptions = new LowLevelList<Exception>();

uint currentThreadId = (uint)Environment.CurrentNativeThreadId;
uint currentThreadId = (uint)Environment.CurrentManagedThreadId;

// Reset nesting levels for exceptions on this thread that might not be currently in flight
foreach (KeyValuePair<Exception, ExceptionData> item in s_exceptionDataTable)
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