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Bug 1346415 - Use FramePointerStackWalk for less deadlocking when stackwalking on x86, r=njn

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MozReview-Commit-ID: CAHarvGSuTY
This commit is contained in:
Michael Layzell
2017-04-18 17:14:40 -04:00
parent ac32a0fe03
commit 81d95ba1f5
4 changed files with 54 additions and 4 deletions
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40
xpcom/threads/ThreadStackHelper.cpp
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@@ -134,6 +134,7 @@ ThreadStackHelper::ThreadStackHelper()
| THREAD_GET_CONTEXT | THREAD_QUERY_INFORMATION
#endif
, FALSE, 0);
mStackTop = profiler_get_stack_top();
MOZ_ASSERT(mInitialized);
#elif defined(XP_MACOSX)
mThreadID = mach_thread_self();
@@ -205,9 +206,14 @@ ThreadStackHelper::GetStackInternal(Stack& aStack, bool aAppendNativeStack)
return;
}
// NOTE: We can only perform frame pointer stack walking on non win64
// platforms, because Win64 always omits frame pointers. We don't want to use
// MozStackWalk here, so we just skip collecting stacks entirely.
#ifndef MOZ_THREADSTACKHELPER_X64
if (aAppendNativeStack) {
aStack.EnsureNativeFrameCapacity(Telemetry::HangStack::sMaxNativeFrames);
}
#endif
if (::SuspendThread(mThreadID) == DWORD(-1)) {
MOZ_ASSERT(false);
@@ -218,22 +224,48 @@ ThreadStackHelper::GetStackInternal(Stack& aStack, bool aAppendNativeStack)
// GetThreadContext to ensure it's really suspended.
// See https://blogs.msdn.microsoft.com/oldnewthing/20150205-00/?p=44743.
CONTEXT context;
memset(&context, 0, sizeof(context));
context.ContextFlags = CONTEXT_CONTROL;
if (::GetThreadContext(mThreadID, &context)) {
FillStackBuffer();
}
#ifndef MOZ_THREADSTACKHELPER_X64
if (aAppendNativeStack) {
auto callback = [](uint32_t, void* aPC, void*, void* aClosure) {
Stack* stack = static_cast<Stack*>(aClosure);
stack->AppendNativeFrame(reinterpret_cast<uintptr_t>(aPC));
};
MozStackWalk(callback, /* skipFrames */ 0,
/* maxFrames */ Telemetry::HangStack::sMaxNativeFrames,
reinterpret_cast<void*>(&aStack),
reinterpret_cast<uintptr_t>(mThreadID), nullptr);
// Now we need to get our frame pointer, our stack pointer, and our stack
// top. Rather than registering and storing the stack tops ourselves, we use
// the gecko profiler to look it up.
void** framePointer = reinterpret_cast<void**>(context.Ebp);
void** stackPointer = reinterpret_cast<void**>(context.Esp);
MOZ_ASSERT(mStackTop, "The thread should be registered by the profiler");
// Double check that the values we pulled for the thread make sense before
// walking the stack.
if (mStackTop && framePointer >= stackPointer && framePointer < mStackTop) {
// NOTE: In bug 1346415 this was changed to use FramePointerStackWalk.
// This was done because lowering the background hang timer threshold
// would cause it to fire on infra early during the boot process, causing
// a deadlock in MozStackWalk when the target thread was holding the
// windows-internal lock on the function table, as it would be suspended
// before we tried to grab the lock to walk its stack.
//
// FramePointerStackWalk is implemented entirely in userspace and thus
// doesn't have the same issues with deadlocking. Unfortunately as 64-bit
// windows is not guaranteed to have frame pointers, the stack walking
// code is only enabled on 32-bit windows builds (bug 1357829).
FramePointerStackWalk(callback, /* skipFrames */ 0,
/* maxFrames */ Telemetry::HangStack::sMaxNativeFrames,
reinterpret_cast<void*>(&aStack), framePointer,
mStackTop);
}
}
#endif
MOZ_ALWAYS_TRUE(::ResumeThread(mThreadID) != DWORD(-1));