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threadsuspend.cpp
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threadsuspend.cpp
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// threadsuspend.CPP
//
// This file contains the implementation of thread suspension. The implementation of thread suspension
// used to be spread through multiple places. That is why, many methods still live in their own homes
// (class Thread, class ThreadStore, etc.). They should be eventually refactored into class ThreadSuspend.
//
#include "common.h"
#include "threadsuspend.h"
#include "finalizerthread.h"
#include "dbginterface.h"
#include "mdaassistants.h"
// from ntstatus.h
#define STATUS_SUSPEND_COUNT_EXCEEDED ((NTSTATUS)0xC000004AL)
#if defined(_TARGET_X86_) || defined(_TARGET_AMD64_) || defined(_TARGET_ARM_)
#define HIJACK_NONINTERRUPTIBLE_THREADS
#endif
bool ThreadSuspend::s_fSuspendRuntimeInProgress = false;
CLREvent* ThreadSuspend::g_pGCSuspendEvent = NULL;
ThreadSuspend::SUSPEND_REASON ThreadSuspend::m_suspendReason;
Thread* ThreadSuspend::m_pThreadAttemptingSuspendForGC;
CLREventBase * ThreadSuspend::s_hAbortEvt = NULL;
CLREventBase * ThreadSuspend::s_hAbortEvtCache = NULL;
// If you add any thread redirection function, make sure the debugger can 1) recognize the redirection
// function, and 2) retrieve the original CONTEXT. See code:Debugger.InitializeHijackFunctionAddress and
// code:DacDbiInterfaceImpl.RetrieveHijackedContext.
extern "C" void RedirectedHandledJITCaseForGCThreadControl_Stub(void);
extern "C" void RedirectedHandledJITCaseForDbgThreadControl_Stub(void);
extern "C" void RedirectedHandledJITCaseForUserSuspend_Stub(void);
extern "C" void RedirectedHandledJITCaseForYieldTask_Stub(void);
#define GetRedirectHandlerForGCThreadControl() \
((PFN_REDIRECTTARGET) GetEEFuncEntryPoint(RedirectedHandledJITCaseForGCThreadControl_Stub))
#define GetRedirectHandlerForDbgThreadControl() \
((PFN_REDIRECTTARGET) GetEEFuncEntryPoint(RedirectedHandledJITCaseForDbgThreadControl_Stub))
#define GetRedirectHandlerForUserSuspend() \
((PFN_REDIRECTTARGET) GetEEFuncEntryPoint(RedirectedHandledJITCaseForUserSuspend_Stub))
#define GetRedirectHandlerForYieldTask() \
((PFN_REDIRECTTARGET) GetEEFuncEntryPoint(RedirectedHandledJITCaseForYieldTask_Stub))
#if defined(_TARGET_AMD64_) || defined(_TARGET_ARM_) || defined(_TARGET_ARM64_)
#if defined(HAVE_GCCOVER) && defined(USE_REDIRECT_FOR_GCSTRESS) // GCCOVER
extern "C" void RedirectedHandledJITCaseForGCStress_Stub(void);
#define GetRedirectHandlerForGCStress() \
((PFN_REDIRECTTARGET) GetEEFuncEntryPoint(RedirectedHandledJITCaseForGCStress_Stub))
#endif // HAVE_GCCOVER && USE_REDIRECT_FOR_GCSTRESS
#endif // _TARGET_AMD64_ || _TARGET_ARM_
// Every PING_JIT_TIMEOUT ms, check to see if a thread in JITted code has wandered
// into some fully interruptible code (or should have a different hijack to improve
// our chances of snagging it at a safe spot).
#define PING_JIT_TIMEOUT 10
// When we find a thread in a spot that's not safe to abort -- how long to wait before
// we try again.
#define ABORT_POLL_TIMEOUT 10
#ifdef _DEBUG
#define ABORT_FAIL_TIMEOUT 40000
#endif // _DEBUG
//
// CANNOT USE IsBad*Ptr() methods here. They are *banned* APIs because of various
// reasons (see http://winweb/wincet/bannedapis.htm).
//
#define IS_VALID_WRITE_PTR(addr, size) _ASSERTE(addr != NULL)
#define IS_VALID_CODE_PTR(addr) _ASSERTE(addr != NULL)
void ThreadSuspend::SetSuspendRuntimeInProgress()
{
LIMITED_METHOD_CONTRACT;
_ASSERTE(ThreadStore::HoldingThreadStore() || IsAtProcessExit());
_ASSERTE(!s_fSuspendRuntimeInProgress || IsAtProcessExit());
s_fSuspendRuntimeInProgress = true;
}
void ThreadSuspend::ResetSuspendRuntimeInProgress()
{
LIMITED_METHOD_CONTRACT;
_ASSERTE(ThreadStore::HoldingThreadStore() || IsAtProcessExit());
_ASSERTE(s_fSuspendRuntimeInProgress || IsAtProcessExit());
s_fSuspendRuntimeInProgress = false;
}
// When SuspendThread returns, target thread may still be executing user code.
// We can not access data, e.g. m_fPreemptiveGCDisabled, changed by target thread.
// But our code depends on reading these data. To make this operation safe, we
// call GetThreadContext which returns only after target thread does not execute
// any user code.
// Message from David Cutler
/*
After SuspendThread returns, can the suspended thread continue to execute code in user mode?
[David Cutler] The suspended thread cannot execute any more user code, but it might be currently "running"
on a logical processor whose other logical processor is currently actually executing another thread.
In this case the target thread will not suspend until the hardware switches back to executing instructions
on its logical processor. In this case even the memory barrier would not necessarily work - a better solution
would be to use interlocked operations on the variable itself.
After SuspendThread returns, does the store buffer of the CPU for the suspended thread still need to drain?
Historically, we've assumed that the answer to both questions is No. But on one 4/8 hyper-threaded machine
running Win2K3 SP1 build 1421, we've seen two stress failures where SuspendThread returns while writes seem to still be in flight.
Usually after we suspend a thread, we then call GetThreadContext. This seems to guarantee consistency.
But there are places we would like to avoid GetThreadContext, if it's safe and legal.
[David Cutler] Get context delivers a APC to the target thread and waits on an event that will be set
when the target thread has delivered its context.
Chris.
*/
// Message from Neill Clift
/*
What SuspendThread does is insert an APC block into a target thread and request an inter-processor interrupt to
do the APC interrupt. It doesn't wait till the thread actually enters some state or the interrupt has been serviced.
I took a quick look at the APIC spec in the Intel manuals this morning. Writing to the APIC posts a message on a bus.
Processors accept messages and presumably queue the s/w interrupts at this time. We don't wait for this acceptance
when we send the IPI so at least on APIC machines when you suspend a thread it continues to execute code for some short time
after the routine returns. We use other mechanisms for IPI and so it could work differently on different h/w.
*/
BOOL EnsureThreadIsSuspended (HANDLE hThread, Thread* pThread)
{
STATIC_CONTRACT_NOTHROW;
STATIC_CONTRACT_GC_NOTRIGGER;
WRAPPER_NO_CONTRACT;
CONTEXT ctx;
ctx.ContextFlags = CONTEXT_INTEGER;
BOOL ret;
ret = ::GetThreadContext(hThread, &ctx);
return ret;
}
FORCEINLINE VOID MyEnterLogLock()
{
EnterLogLock();
}
FORCEINLINE VOID MyLeaveLogLock()
{
LeaveLogLock();
}
// On non-Windows CORECLR platforms remove Thread::SuspendThread support
#ifndef DISABLE_THREADSUSPEND
// SuspendThread
// Attempts to OS-suspend the thread, whichever GC mode it is in.
// Arguments:
// fOneTryOnly - If TRUE, report failure if the thread has its
// m_dwForbidSuspendThread flag set. If FALSE, retry.
// pdwSuspendCount - If non-NULL, will contain the return code
// of the underlying OS SuspendThread call on success,
// undefined on any kind of failure.
// Return value:
// A SuspendThreadResult value indicating success or failure.
Thread::SuspendThreadResult Thread::SuspendThread(BOOL fOneTryOnly, DWORD *pdwSuspendCount)
{
CONTRACTL {
NOTHROW;
GC_NOTRIGGER;
}
CONTRACTL_END;
#ifdef STRESS_LOG
if (StressLog::StressLogOn((unsigned int)-1, 0))
{
// Make sure to create the stress log for the current thread
// (if needed) before we suspend the target thread. The target
// thread may be holding the stress log lock when we suspend it,
// which could cause a deadlock.
if (StressLog::CreateThreadStressLog() == NULL)
{
return STR_NoStressLog;
}
}
#endif
Volatile<HANDLE> hThread;
SuspendThreadResult str = (SuspendThreadResult) -1;
DWORD dwSuspendCount = 0;
DWORD tries = 1;
#if defined(_DEBUG)
int nCnt = 0;
bool bDiagSuspend = g_pConfig->GetDiagnosticSuspend();
ULONGLONG i64TimestampStart = CLRGetTickCount64();
ULONGLONG i64TimestampCur = i64TimestampStart;
ULONGLONG i64TimestampPrev = i64TimestampStart;
// This is the max allowed timestamp ticks to transpire from beginning of
// our attempt to suspend the thread, before we'll assert (implying we believe
// there might be a deadlock) - (default = 2000).
ULONGLONG i64TimestampTicksMax = g_pConfig->SuspendThreadDeadlockTimeoutMs();
#endif // _DEBUG
#if defined(_DEBUG)
// Stop the stress log from allocating any new memory while in this function
// as that can lead to deadlocks
CantAllocHolder hldrCantAlloc;
#endif
DWORD dwSwitchCount = 0;
while (TRUE) {
StateHolder<MyEnterLogLock, MyLeaveLogLock> LogLockHolder(FALSE);
CounterHolder handleHolder(&m_dwThreadHandleBeingUsed);
// Whether or not "goto retry" should YieldProcessor and __SwitchToThread
BOOL doSwitchToThread = TRUE;
hThread = GetThreadHandle();
if (hThread == INVALID_HANDLE_VALUE) {
str = STR_UnstartedOrDead;
break;
}
else if (hThread == SWITCHOUT_HANDLE_VALUE) {
str = STR_SwitchedOut;
break;
}
{
// We do not want to suspend the target thread while it is holding the log lock.
// By acquiring the lock ourselves, we know that this is not the case.
LogLockHolder.Acquire();
// It is important to avoid two threads suspending each other.
// Before a thread suspends another, it increments its own m_dwForbidSuspendThread count first,
// then it checks the target thread's m_dwForbidSuspendThread.
ForbidSuspendThreadHolder forbidSuspend;
if ((m_dwForbidSuspendThread != 0))
{
#if defined(_DEBUG)
// Enable the diagnostic ::SuspendThread() if the
// DiagnosticSuspend config setting is set.
// This will interfere with the mutual suspend race but it's
// here only for diagnostic purposes anyway
if (!bDiagSuspend)
#endif // _DEBUG
goto retry;
}
dwSuspendCount = ::SuspendThread(hThread);
//
// Since SuspendThread is asynchronous, we now must wait for the thread to
// actually be suspended before decrementing our own m_dwForbidSuspendThread count.
// Otherwise there would still be a chance for the "suspended" thread to suspend us
// before it really stops running.
//
if ((int)dwSuspendCount >= 0)
{
if (!EnsureThreadIsSuspended(hThread, this))
{
::ResumeThread(hThread);
str = STR_Failure;
break;
}
}
}
if ((int)dwSuspendCount >= 0)
{
if (hThread == GetThreadHandle())
{
if (m_dwForbidSuspendThread != 0)
{
#if defined(_DEBUG)
// Log diagnostic below 8 times during the i64TimestampTicksMax period
if (i64TimestampCur-i64TimestampStart >= nCnt*(i64TimestampTicksMax>>3) )
{
CONTEXT ctx;
SetIP(&ctx, -1);
ctx.ContextFlags = CONTEXT_CONTROL;
this->GetThreadContext(&ctx);
STRESS_LOG7(LF_SYNC, LL_INFO1000,
"Thread::SuspendThread[%p]: EIP=%p. nCnt=%d. result=%d.\n"
"\t\t\t\t\t\t\t\t\t forbidSuspend=%d. coop=%d. state=%x.\n",
this, GetIP(&ctx), nCnt, dwSuspendCount,
(LONG)this->m_dwForbidSuspendThread, (ULONG)this->m_fPreemptiveGCDisabled, this->GetSnapshotState());
// Enable a preemptive assert in diagnostic mode: before we
// resume the target thread to get its current state in the debugger
if (bDiagSuspend)
{
// triggered after 6 * 250msec
_ASSERTE(nCnt < 6 && "Timing out in Thread::SuspendThread");
}
++nCnt;
}
#endif // _DEBUG
::ResumeThread(hThread);
#if defined(_DEBUG)
// If the suspend diagnostics are enabled we need to spin here in order to avoid
// the case where we Suspend/Resume the target thread without giving it a chance to run.
if ((!fOneTryOnly) && bDiagSuspend)
{
while ( m_dwForbidSuspendThread != 0 &&
CLRGetTickCount64()-i64TimestampStart < nCnt*(i64TimestampTicksMax>>3) )
{
if (g_SystemInfo.dwNumberOfProcessors > 1)
{
if ((tries++) % 20 != 0)
{
YieldProcessor(); // play nice on hyperthreaded CPUs
} else {
__SwitchToThread(0, ++dwSwitchCount);
}
}
else
{
__SwitchToThread(0, ++dwSwitchCount); // don't spin on uniproc machines
}
}
}
#endif // _DEBUG
goto retry;
}
// We suspend the right thread
#ifdef _DEBUG
Thread * pCurThread = GetThread();
if (pCurThread != NULL)
{
pCurThread->dbg_m_cSuspendedThreads ++;
_ASSERTE(pCurThread->dbg_m_cSuspendedThreads > 0);
}
#endif
IncCantAllocCount();
m_ThreadHandleForResume = hThread;
str = STR_Success;
break;
}
else
{
// A thread was switch out but in again.
// We suspend a wrong thread.
::ResumeThread(hThread);
doSwitchToThread = FALSE;
goto retry;
}
}
else {
// We can get here either SuspendThread fails
// Or the fiber thread dies after this fiber switched out.
if ((int)dwSuspendCount != -1) {
STRESS_LOG1(LF_SYNC, LL_INFO1000, "In Thread::SuspendThread ::SuspendThread returned %x\n", dwSuspendCount);
}
if (GetThreadHandle() == SWITCHOUT_HANDLE_VALUE) {
str = STR_SwitchedOut;
break;
}
else {
// Our callers generally expect that STR_Failure means that
// the thread has exited.
#ifndef FEATURE_PAL
_ASSERTE(NtCurrentTeb()->LastStatusValue != STATUS_SUSPEND_COUNT_EXCEEDED);
#endif // !FEATURE_PAL
str = STR_Failure;
break;
}
}
retry:
handleHolder.Release();
LogLockHolder.Release();
if (fOneTryOnly)
{
str = STR_Forbidden;
break;
}
#if defined(_DEBUG)
i64TimestampPrev = i64TimestampCur;
i64TimestampCur = CLRGetTickCount64();
// CLRGetTickCount64() is global per machine (not per CPU, like getTimeStamp()).
// Next ASSERT states that CLRGetTickCount64() is increasing, or has wrapped.
// If it wrapped, the last iteration should have executed faster then 0.5 seconds.
_ASSERTE(i64TimestampCur >= i64TimestampPrev || i64TimestampCur <= 500);
if (i64TimestampCur - i64TimestampStart >= i64TimestampTicksMax)
{
dwSuspendCount = ::SuspendThread(hThread);
_ASSERTE(!"It takes too long to suspend a thread");
if ((int)dwSuspendCount >= 0)
::ResumeThread(hThread);
}
#endif // _DEBUG
if (doSwitchToThread)
{
// When looking for deadlocks we need to allow the target thread to run in order to make some progress.
// On multi processor machines we saw the suspending thread resuming immediately after the __SwitchToThread()
// because it has another few processors available. As a consequence the target thread was being Resumed and
// Suspended right away, w/o a real chance to make any progress.
if (g_SystemInfo.dwNumberOfProcessors > 1)
{
if ((tries++) % 20 != 0) {
YieldProcessor(); // play nice on hyperthreaded CPUs
} else {
__SwitchToThread(0, ++dwSwitchCount);
}
}
else
{
__SwitchToThread(0, ++dwSwitchCount); // don't spin on uniproc machines
}
}
}
#ifdef PROFILING_SUPPORTED
{
BEGIN_PIN_PROFILER(CORProfilerTrackSuspends());
if (str == STR_Success)
{
g_profControlBlock.pProfInterface->RuntimeThreadSuspended((ThreadID)this);
}
END_PIN_PROFILER();
}
#endif // PROFILING_SUPPORTED
if (pdwSuspendCount != NULL)
{
*pdwSuspendCount = dwSuspendCount;
}
_ASSERTE(str != (SuspendThreadResult) -1);
return str;
}
#endif // DISABLE_THREADSUSPEND
// On non-Windows CORECLR platforms remove Thread::ResumeThread support
#ifndef DISABLE_THREADSUSPEND
DWORD Thread::ResumeThread()
{
CONTRACTL
{
NOTHROW;
GC_NOTRIGGER;
SO_TOLERANT;
MODE_ANY;
}
CONTRACTL_END;
_ASSERTE (m_ThreadHandleForResume != INVALID_HANDLE_VALUE);
#ifdef FEATURE_INCLUDE_ALL_INTERFACES
_ASSERTE (m_pHostTask == 0 || GetThreadHandle() != SWITCHOUT_HANDLE_VALUE);
#else // !FEATURE_INCLUDE_ALL_INTERFACES
_ASSERTE (GetThreadHandle() != SWITCHOUT_HANDLE_VALUE);
#endif // FEATURE_INCLUDE_ALL_INTERFACES
//DWORD res = ::ResumeThread(GetThreadHandle());
DWORD res = ::ResumeThread(m_ThreadHandleForResume);
_ASSERTE (res != 0 && "Thread is not previously suspended");
#ifdef _DEBUG_IMPL
_ASSERTE (!m_Creater.IsCurrentThread());
if ((res != (DWORD)-1) && (res != 0))
{
Thread * pCurThread = GetThread();
if (pCurThread != NULL)
{
_ASSERTE(pCurThread->dbg_m_cSuspendedThreads > 0);
pCurThread->dbg_m_cSuspendedThreads --;
_ASSERTE(pCurThread->dbg_m_cSuspendedThreadsWithoutOSLock <= pCurThread->dbg_m_cSuspendedThreads);
}
}
#endif
if (res != (DWORD) -1 && res != 0)
{
DecCantAllocCount();
}
#ifdef PROFILING_SUPPORTED
{
BEGIN_PIN_PROFILER(CORProfilerTrackSuspends());
if ((res != 0) && (res != (DWORD)-1))
{
g_profControlBlock.pProfInterface->RuntimeThreadResumed((ThreadID)this);
}
END_PIN_PROFILER();
}
#endif
return res;
}
#endif // DISABLE_THREADSUSPEND
#ifdef _DEBUG
void* forceStackA;
// CheckSuspended
// Checks whether the given thread is currently suspended.
// Note that if we cannot determine the true suspension status
// of the thread, we succeed. Intended to be used in asserts
// in operations that require the target thread to be suspended.
// Arguments:
// pThread - The thread to examine.
// Return value:
// FALSE, if the thread is definitely not suspended.
// TRUE, otherwise.
static inline BOOL CheckSuspended(Thread *pThread)
{
CONTRACTL
{
NOTHROW;
GC_NOTRIGGER;
DEBUG_ONLY;
}
CONTRACTL_END;
_ASSERTE(GetThread() != pThread);
_ASSERTE(CheckPointer(pThread));
#ifndef DISABLE_THREADSUSPEND
// Only perform this test if we're allowed to call back into the host.
// Thread::SuspendThread contains several potential calls into the host.
if (CanThisThreadCallIntoHost())
{
DWORD dwSuspendCount;
Thread::SuspendThreadResult str = pThread->SuspendThread(FALSE, &dwSuspendCount);
forceStackA = &dwSuspendCount;
if (str == Thread::STR_Success)
{
pThread->ResumeThread();
return dwSuspendCount >= 1;
}
}
#endif // !DISABLE_THREADSUSPEND
return TRUE;
}
#endif //_DEBUG
BOOL EEGetThreadContext(Thread *pThread, CONTEXT *pContext)
{
CONTRACTL {
NOTHROW;
GC_NOTRIGGER;
}
CONTRACTL_END;
_ASSERTE(CheckSuspended(pThread));
BOOL ret = pThread->GetThreadContext(pContext);
STRESS_LOG6(LF_SYNC, LL_INFO1000, "Got thread context ret = %d EIP = %p ESP = %p EBP = %p, pThread = %p, ContextFlags = 0x%x\n",
ret, GetIP(pContext), GetSP(pContext), GetFP(pContext), pThread, pContext->ContextFlags);
return ret;
}
BOOL EESetThreadContext(Thread *pThread, const CONTEXT *pContext)
{
CONTRACTL {
NOTHROW;
GC_NOTRIGGER;
}
CONTRACTL_END;
#ifdef _TARGET_X86_
_ASSERTE(CheckSuspended(pThread));
#endif
BOOL ret = pThread->SetThreadContext(pContext);
STRESS_LOG6(LF_SYNC, LL_INFO1000, "Set thread context ret = %d EIP = %p ESP = %p EBP = %p, pThread = %p, ContextFlags = 0x%x\n",
ret, GetIP((CONTEXT*)pContext), GetSP((CONTEXT*)pContext), GetFP((CONTEXT*)pContext), pThread, pContext->ContextFlags);
return ret;
}
// The AbortReason must be cleared at the following times:
//
// 1. When the application performs a ResetAbort.
//
// 2. When the physical thread stops running. That's because we must eliminate any
// cycles that would otherwise be uncollectible, between the Reason and the Thread.
// Nobody can retrieve the Reason after the thread stops running anyway.
//
// We don't have to do any work when the AppDomain containing the Reason object is unloaded.
// That's because the HANDLE is released as part of the tear-down. The 'adid' prevents us
// from ever using the trash handle value thereafter.
void Thread::ClearAbortReason(BOOL pNoLock)
{
CONTRACTL
{
GC_NOTRIGGER;
MODE_COOPERATIVE;
NOTHROW;
}
CONTRACTL_END;
OBJECTHANDLE oh;
ADID adid;
if (pNoLock){
// Stash the fields so we can destroy the OBJECTHANDLE if appropriate.
oh = m_AbortReason;
adid = m_AbortReasonDomainID;
// Clear the fields.
m_AbortReason = 0;
m_AbortReasonDomainID = ADID(INVALID_APPDOMAIN_ID);
}
else
// Scope the lock to stashing and clearing the two fields on the Thread object.
{
// Atomically get the OBJECTHANDLE and ADID of the object, and then
// clear them.
// NOTE: get the lock on this thread object, not on the executing thread.
Thread::AbortRequestLockHolder lock(this);
// Stash the fields so we can destroy the OBJECTHANDLE if appropriate.
oh = m_AbortReason;
adid = m_AbortReasonDomainID;
// Clear the fields.
m_AbortReason = 0;
m_AbortReasonDomainID = ADID(INVALID_APPDOMAIN_ID);
}
// If there is an OBJECTHANDLE, try to clear it.
if (oh != 0 && adid.m_dwId != 0)
{ // See if the domain is still valid; if so, destroy the ObjectHandle
AppDomainFromIDHolder ad(adid, TRUE);
if (!ad.IsUnloaded())
{ // Still a valid domain, so destroy the handle.
DestroyHandle(oh);
}
}
}
// Context passed down through a stack crawl (see code below).
struct StackCrawlContext
{
enum SCCType
{
SCC_CheckWithinEH = 0x00000001,
SCC_CheckWithinCer = 0x00000002,
};
Thread* pAbortee;
int eType;
BOOL fUnprotectedCode;
BOOL fWithinEHClause;
BOOL fWithinCer;
BOOL fHasManagedCodeOnStack;
BOOL fWriteToStressLog;
BOOL fHaveLatchedCF;
CrawlFrame LatchedCF;
};
#if _TARGET_AMD64_
// Returns the PC for the next instruction
// If you want to skip ahead of a NOP padding sequence
// You'll need to call this thing multiple times, until it returns NULL
#define NOP_REX_PREFIX ((char)0x66)
#define XCHG_EAX_EAX ((char)0x90)
int isAtNop(const void *ip)
{
const char *NextByte = (const char *)ip;
STRESS_LOG1(LF_EH, LL_INFO100, "AMD64 - isAtNop ip 0x%p\n", ip);
int lpfxCount = 0;
//
// Read in length prefixes - no effect
//
for (lpfxCount = 0; lpfxCount < 14; lpfxCount++)
{
if (NextByte[lpfxCount] != NOP_REX_PREFIX)
break;
}
//
// xchg eax, eax
//
if (NextByte[lpfxCount] == XCHG_EAX_EAX)
return (lpfxCount + 1);
return 0;
}
#endif // _TARGET_AMD64_
// Crawl the stack looking for Thread Abort related information (whether we're executing inside a CER or an error handling clauses
// of some sort).
static StackWalkAction TAStackCrawlCallBackWorker(CrawlFrame* pCf, StackCrawlContext *pData)
{
CONTRACTL {
NOTHROW;
GC_NOTRIGGER;
}
CONTRACTL_END;
_ASSERTE(pData->eType & (StackCrawlContext::SCC_CheckWithinCer | StackCrawlContext::SCC_CheckWithinEH));
if(pCf->IsFrameless())
{
IJitManager* pJitManager = pCf->GetJitManager();
_ASSERTE(pJitManager);
if (pJitManager && !pData->fHasManagedCodeOnStack)
{
pData->fHasManagedCodeOnStack = TRUE;
}
}
// Get the method for this frame if it exists (might not be a managed method, so check the explicit frame if that's what we're
// looking at).
MethodDesc *pMD = pCf->GetFunction();
Frame *pFrame = pCf->GetFrame();
if (pMD == NULL && pFrame != NULL)
pMD = pFrame->GetFunction();
// Non-method frames don't interest us.
if (pMD == NULL)
return SWA_CONTINUE;
#if defined(_DEBUG)
#define METHODNAME(pFunc) (pFunc?pFunc->m_pszDebugMethodName:"<n/a>")
#else
#define METHODNAME(pFunc) "<n/a>"
#endif
if (pData->fWriteToStressLog)
{
STRESS_LOG5(LF_EH, LL_INFO100, "TAStackCrawlCallBack: STACKCRAWL method:%pM ('%s'), offset %x, Frame:%p, FrameVtable = %pV\n",
pMD, METHODNAME(pMD), pCf->IsFrameless()?pCf->GetRelOffset():0, pFrame, pCf->IsFrameless()?0:(*(void**)pFrame));
}
#undef METHODNAME
// If we're asking about CERs and we don't yet have a definite answer either way then take a closer look at the current method.
if (pData->eType & StackCrawlContext::SCC_CheckWithinCer && !pData->fUnprotectedCode && !pData->fWithinCer)
{
// Check for CER root methods (these are never inlined). If we've found one of these at the root of a bunch of potential CER
// methods (i.e. those with a compatible reliability contract) then we're executing in a CER.
if (IsCerRootMethod(pMD))
pData->fWithinCer = true;
// Only need to look deeper if we couldn't decide if we're in a CER yet.
if (!pData->fWithinCer)
{
// IL stubs are transparent to CERs.
if (!pMD->IsILStub())
// Check for reliability contracts on the method (and class and assembly). If it's high enough level to be included
// in a CER then we can continue (hopefully finding a CER root method further down the stack). Otherwise we've got
// at least one method that's not part of a CER on the top of the stack so we're definitely not executing within a
// CER.
if (CheckForReliabilityContract(pMD) < RCL_BASIC_CONTRACT)
pData->fUnprotectedCode = true;
}
}
// If we weren't asked about EH clauses then we can return now (stop the stack trace if we have a definitive answer on the CER
// question, move to the next frame otherwise).
if ((pData->eType & StackCrawlContext::SCC_CheckWithinEH) == 0)
return ((pData->fWithinCer || pData->fUnprotectedCode) && pData->fHasManagedCodeOnStack) ? SWA_ABORT : SWA_CONTINUE;
// If we already discovered we're within an EH clause but are still processing (presumably to determine whether we're within a
// CER), then we can just skip to the next frame straight away. Also terminate here if the current frame is not frameless since
// there isn't any useful EH information for non-managed frames.
if (pData->fWithinEHClause || !pCf->IsFrameless())
return SWA_CONTINUE;
IJitManager* pJitManager = pCf->GetJitManager();
_ASSERTE(pJitManager);
EH_CLAUSE_ENUMERATOR pEnumState;
unsigned EHCount = pJitManager->InitializeEHEnumeration(pCf->GetMethodToken(), &pEnumState);
if (EHCount == 0)
// We do not have finally clause here.
return SWA_CONTINUE;
DWORD offs = (DWORD)pCf->GetRelOffset();
if (!pCf->IsActiveFrame())
{
// If we aren't the topmost method, then our IP is a return address and
// we can't use it to directly compare against the EH ranges because we
// may be in an cloned finally which has a call as the last instruction.
offs--;
}
if (pData->fWriteToStressLog)
{
STRESS_LOG1(LF_EH, LL_INFO100, "TAStackCrawlCallBack: STACKCRAWL Offset 0x%x V\n", offs);
}
EE_ILEXCEPTION_CLAUSE EHClause;
StackWalkAction action = SWA_CONTINUE;
#ifdef _TARGET_X86_
// On X86, the EH encoding for catch clause is completely mess.
// If catch clause is in its own basic block, the end of catch includes everything in the basic block.
// For nested catch, the end of catch may include several jmp instructions after JIT_EndCatch call.
// To better decide if we are inside a nested catch, we check if offs-1 is in more than one catch clause.
DWORD countInCatch = 0;
BOOL fAtJitEndCatch = FALSE;
if (pData->pAbortee == GetThread() &&
pData->pAbortee->ThrewControlForThread() == Thread::InducedThreadRedirectAtEndOfCatch &&
GetControlPC(pCf->GetRegisterSet()) == (PCODE)GetIP(pData->pAbortee->GetAbortContext()))
{
fAtJitEndCatch = TRUE;
offs -= 1;
}
#endif // _TARGET_X86_
#if _TARGET_AMD64_
STRESS_LOG1(LF_EH, LL_INFO10, "AMD64 - in TAStackCrawlCallBack 0x%x offset\n", offs);
STRESS_LOG1(LF_EH, LL_INFO10, "AMD64 - in TAStackCrawlCallBack frame IP is 0x%p\n", (void *)GetControlPC(pCf->GetRegisterSet()));
STRESS_LOG3(LF_EH, LL_INFO100, "AMD64 - in TAStackCrawlCallBack: STACKCRAWL method:%pM (), Frame:%p, FrameVtable = %pV\n",
pMD, pFrame, pCf->IsFrameless()?0:(*(void**)pFrame));
DWORD OffsSkipNop = offs;
if ( pCf->IsFrameless() && pCf->IsActiveFrame())
{
// If the frame is the top most frame and is managed,
// get the ip
void *oldIP = (void *)GetControlPC(pCf->GetRegisterSet());
// skip over the nop to get newIP
int bNop = isAtNop(oldIP);
// Skip over the nop if any
OffsSkipNop += bNop;
if (bNop != 0)
{
STRESS_LOG1(LF_EH, LL_INFO100, "AMD64 - TAStackCrawlCallBack: STACKCRAWL new Offset 0x%x V\n", OffsSkipNop );
}
}
#endif // _TARGET_AMD64_
for(ULONG i=0; i < EHCount; i++)
{
pJitManager->GetNextEHClause(&pEnumState, &EHClause);
_ASSERTE(IsValidClause(&EHClause));
#if _TARGET_AMD64_
if (offs != OffsSkipNop && OffsSkipNop == EHClause.TryStartPC)
{
// Ensure that the new offset isnt landing us into a cloned finally
// that "appears" to have a try-block which starts with a non-NOP
// instruction when actually its a cloned finally.
if (!IsClonedFinally(&EHClause))
{
// If we are at the nop instruction injected by JIT right before a try catch,
// we don't want to async abort. This is a workaround to address issue with the C# lock statement bug,
// where we could end up leaking a lock.
//
STRESS_LOG1(LF_EH, LL_INFO100, "AMD64 - TAStackCrawlCallBack: STACKCRAWL AMD64 TA at beginning of a Try catch 0x%x \n", OffsSkipNop );
pData->fWithinEHClause = true;
return SWA_ABORT;
}
}
#endif // _TARGET_AMD64_
// !!! If this function is called on Aborter thread, we should check for finally only.
// !!! If this function is called on Aborter thread, we should check for finally only.
// !!! Catch and filter clause are skipped. In UserAbort, the first thing after ReadyForAbort
// !!! is to check if the target thread is processing exception.
// !!! If exception is in flight, we don't induce ThreadAbort. Instead at the end of Jit_EndCatch
// !!! we will handle abort.
if (pData->pAbortee != GetThread() && !IsFaultOrFinally(&EHClause))
{
continue;
}
if (offs >= EHClause.HandlerStartPC &&
offs < EHClause.HandlerEndPC)
{
#ifdef _TARGET_X86_
if (fAtJitEndCatch)
{
// On X86, JIT's EH info may include the instruction after JIT_EndCatch inside the same catch
// clause if it is in the same basic block.
// So for this case, the offs is in at least one catch handler, but since we are at the end of
// catch, this one should not be counted.
countInCatch ++;
if (countInCatch == 1)
{
continue;
}
}
#endif
pData->fWithinEHClause = true;
// We're within an EH clause. If we're asking about CERs too then stop the stack walk if we've reached a conclusive
// result or continue looking otherwise. Else we can stop the stackwalk now.
if (pData->eType & StackCrawlContext::SCC_CheckWithinCer)
{
action = (pData->fWithinCer || pData->fUnprotectedCode) ? SWA_ABORT : SWA_CONTINUE;
}
else
{
action = SWA_ABORT;
}
break;
}
}
#ifdef _TARGET_X86_
#ifdef _DEBUG
if (fAtJitEndCatch)
{
_ASSERTE (countInCatch > 0);
}
#endif // _DEBUG
#endif // _TARGET_X86_
return action;
}
// Wrapper around code:TAStackCrawlCallBackWorker that abstracts away the differences between the reporting order
// of x86 and 64-bit stackwalker implementations, and also deals with interop calls that have an implicit reliability
// contract. If a P/Invoke or CLR->COM call returns SafeHandle or CriticalHandle, the IL stub could be aborted
// before having a chance to store the native handle into the Safe/CriticalHandle object. Therefore such calls are
// treated as unbreakable by convention.
StackWalkAction TAStackCrawlCallBack(CrawlFrame* pCf, void* data)
{
CONTRACTL {
NOTHROW;
GC_NOTRIGGER;
}
CONTRACTL_END;
StackCrawlContext *pData = (StackCrawlContext *)data;
// We have the current frame in pCf and possibly one latched frame in pData->LatchedCF. This enumeration
// describes which of these should be passed to code:TAStackCrawlCallBackWorker and in what order.
enum LatchedFrameAction
{
DiscardLatchedFrame, // forget the latched frame, report the current one
DiscardCurrentFrame, // ignore the current frame, report the latched one
ProcessLatchedInOrder, // report the latched frame, then report the current frame
ProcessLatchedReversed, // report the current frame, then report the latched frame
LatchCurrentFrame // latch the current frame, don't report anything
}
frameAction = DiscardLatchedFrame;
#ifdef _TARGET_X86_
// On X86 the IL stub method is reported to us before the frame with the actual interop method. We need to
// swap the order because if the worker saw the IL stub - which is a CER root - first, it would terminate the
// stack walk and wouldn't allow the thread to be aborted, regardless of how the interop method is annotated.
if (pData->fHaveLatchedCF)
{
// Does the current and latched frame represent the same call?
if (pCf->pFrame == pData->LatchedCF.pFrame)
{
if (pData->LatchedCF.GetFunction()->AsDynamicMethodDesc()->IsUnbreakable())
{
// Report only the latched IL stub frame which is a CER root.
frameAction = DiscardCurrentFrame;
}
else
{
// Report the interop method (current frame) which may be annotated, then the IL stub.
frameAction = ProcessLatchedReversed;
}
}
else
{
// The two frames are unrelated - process them in order.
frameAction = ProcessLatchedInOrder;
}
pData->fHaveLatchedCF = FALSE;
}
else
{
MethodDesc *pMD = pCf->GetFunction();
if (pMD != NULL && pMD->IsILStub() && InlinedCallFrame::FrameHasActiveCall(pCf->pFrame))
{
// This may be IL stub for an interesting interop call - latch it.