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Revert "Use FLS detach as thread termination notification on windows. (…
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…dotnet#110589)" (dotnet#110801)

This reverts commit 69d8076.
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@jkotas
jkotas authored Dec 18, 2024
1 parent bee5ab7 commit 237c759
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Showing 4 changed files with 31 additions and 140 deletions.
2 changes: 1 addition & 1 deletion src/coreclr/nativeaot/Runtime/threadstore.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,7 @@ void ThreadStore::DetachCurrentThread()
}

// Unregister from OS notifications
// This can return false if a thread did not register for OS notification.
// This can return false if detach notification is spurious and does not belong to this thread.
if (!PalDetachThread(pDetachingThread))
{
return;
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152 changes: 30 additions & 122 deletions src/coreclr/vm/ceemain.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1701,125 +1701,6 @@ BOOL STDMETHODCALLTYPE EEDllMain( // TRUE on success, FALSE on error.

#endif // !defined(CORECLR_EMBEDDED)

static void RuntimeThreadShutdown(void* thread)
{
Thread* pThread = (Thread*)thread;
_ASSERTE(pThread == GetThreadNULLOk());

if (pThread)
{
#ifdef FEATURE_COMINTEROP
// reset the CoInitialize state
// so we don't call CoUninitialize during thread detach
pThread->ResetCoInitialized();
#endif // FEATURE_COMINTEROP
// For case where thread calls ExitThread directly, we need to reset the
// frame pointer. Otherwise stackwalk would AV. We need to do it in cooperative mode.
// We need to set m_GCOnTransitionsOK so this thread won't trigger GC when toggle GC mode
if (pThread->m_pFrame != FRAME_TOP)
{
#ifdef _DEBUG
pThread->m_GCOnTransitionsOK = FALSE;
#endif
GCX_COOP_NO_DTOR();
pThread->m_pFrame = FRAME_TOP;
GCX_COOP_NO_DTOR_END();
}

pThread->DetachThread(TRUE);
}
else
{
// Since we don't actually cleanup the TLS data along this path, verify that it is already cleaned up
AssertThreadStaticDataFreed();
}

ThreadDetaching();
}

#ifdef TARGET_WINDOWS

// Index for the fiber local storage of the attached thread pointer
static uint32_t g_flsIndex = FLS_OUT_OF_INDEXES;

// This is called when each *fiber* is destroyed. When the home fiber of a thread is destroyed,
// it means that the thread itself is destroyed.
// Since we receive that notification outside of the Loader Lock, it allows us to safely acquire
// the ThreadStore lock in the RuntimeThreadShutdown.
static void __stdcall FiberDetachCallback(void* lpFlsData)
{
ASSERT(g_flsIndex != FLS_OUT_OF_INDEXES);
ASSERT(lpFlsData == FlsGetValue(g_flsIndex));

if (lpFlsData != NULL)
{
// The current fiber is the home fiber of a thread, so the thread is shutting down
RuntimeThreadShutdown(lpFlsData);
}
}

void InitFlsSlot()
{
// We use fiber detach callbacks to run our thread shutdown code because the fiber detach
// callback is made without the OS loader lock
g_flsIndex = FlsAlloc(FiberDetachCallback);
if (g_flsIndex == FLS_OUT_OF_INDEXES)
{
COMPlusThrowWin32();
}
}

// Register the thread with OS to be notified when thread is about to be destroyed
// It fails fast if a different thread was already registered with the current fiber.
// Parameters:
// thread - thread to attach
static void OsAttachThread(void* thread)
{
void* threadFromCurrentFiber = FlsGetValue(g_flsIndex);

if (threadFromCurrentFiber != NULL)
{
_ASSERTE_ALL_BUILDS(!"Multiple threads encountered from a single fiber");
}

// Associate the current fiber with the current thread. This makes the current fiber the thread's "home"
// fiber. This fiber is the only fiber allowed to execute managed code on this thread. When this fiber
// is destroyed, we consider the thread to be destroyed.
FlsSetValue(g_flsIndex, thread);
}

// Detach thread from OS notifications.
// It fails fast if some other thread value was attached to the current fiber.
// Parameters:
// thread - thread to detach
// Return:
// true if the thread was detached, false if there was no attached thread
void OsDetachThread(void* thread)
{
ASSERT(g_flsIndex != FLS_OUT_OF_INDEXES);
void* threadFromCurrentFiber = FlsGetValue(g_flsIndex);

if (threadFromCurrentFiber == NULL)
{
// we've seen this thread, but not this fiber. It must be a "foreign" fiber that was
// borrowing this thread.
return;
}

if (threadFromCurrentFiber != thread)
{
_ASSERTE_ALL_BUILDS(!"Detaching a thread from the wrong fiber");
}

FlsSetValue(g_flsIndex, NULL);
}

void EnsureTlsDestructionMonitor()
{
OsAttachThread(GetThread());
}

#else
struct TlsDestructionMonitor
{
bool m_activated = false;
Expand All @@ -1833,7 +1714,36 @@ struct TlsDestructionMonitor
{
if (m_activated)
{
RuntimeThreadShutdown(GetThreadNULLOk());
Thread* thread = GetThreadNULLOk();
if (thread)
{
#ifdef FEATURE_COMINTEROP
// reset the CoInitialize state
// so we don't call CoUninitialize during thread detach
thread->ResetCoInitialized();
#endif // FEATURE_COMINTEROP
// For case where thread calls ExitThread directly, we need to reset the
// frame pointer. Otherwise stackwalk would AV. We need to do it in cooperative mode.
// We need to set m_GCOnTransitionsOK so this thread won't trigger GC when toggle GC mode
if (thread->m_pFrame != FRAME_TOP)
{
#ifdef _DEBUG
thread->m_GCOnTransitionsOK = FALSE;
#endif
GCX_COOP_NO_DTOR();
thread->m_pFrame = FRAME_TOP;
GCX_COOP_NO_DTOR_END();
}

thread->DetachThread(TRUE);
}
else
{
// Since we don't actually cleanup the TLS data along this path, verify that it is already cleaned up
AssertThreadStaticDataFreed();
}

ThreadDetaching();
}
}
};
Expand All @@ -1847,8 +1757,6 @@ void EnsureTlsDestructionMonitor()
tls_destructionMonitor.Activate();
}

#endif

#ifdef DEBUGGING_SUPPORTED
//
// InitializeDebugger initialized the Runtime-side COM+ Debugging Services
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4 changes: 0 additions & 4 deletions src/coreclr/vm/ceemain.h
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Original file line number Diff line number Diff line change
Expand Up @@ -46,10 +46,6 @@ void ForceEEShutdown(ShutdownCompleteAction sca = SCA_ExitProcessWhenShutdownCom
void ThreadDetaching();

void EnsureTlsDestructionMonitor();
#ifdef TARGET_WINDOWS
void InitFlsSlot();
void OsDetachThread(void* thread);
#endif

void SetLatchedExitCode (INT32 code);
INT32 GetLatchedExitCode (void);
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13 changes: 0 additions & 13 deletions src/coreclr/vm/threads.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -353,22 +353,13 @@ void SetThread(Thread* t)
{
LIMITED_METHOD_CONTRACT

Thread* origThread = gCurrentThreadInfo.m_pThread;
gCurrentThreadInfo.m_pThread = t;
if (t != NULL)
{
InitializeCurrentThreadsStaticData(t);
EnsureTlsDestructionMonitor();
t->InitRuntimeThreadLocals();
}
#ifdef TARGET_WINDOWS
else if (origThread != NULL)
{
// Unregister from OS notifications
// This can return false if a thread did not register for OS notification.
OsDetachThread(origThread);
}
#endif

// Clear or set the app domain to the one domain based on if the thread is being nulled out or set
gCurrentThreadInfo.m_pAppDomain = t == NULL ? NULL : AppDomain::GetCurrentDomain();
Expand Down Expand Up @@ -1048,10 +1039,6 @@ void InitThreadManager()
}
CONTRACTL_END;

#ifdef TARGET_WINDOWS
InitFlsSlot();
#endif

// All patched helpers should fit into one page.
// If you hit this assert on retail build, there is most likely problem with BBT script.
_ASSERTE_ALL_BUILDS((BYTE*)JIT_PatchedCodeLast - (BYTE*)JIT_PatchedCodeStart > (ptrdiff_t)0);
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