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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef PROFILER_PSEUDO_STACK_H_
#define PROFILER_PSEUDO_STACK_H_
#include "mozilla/ArrayUtils.h"
#include <stdint.h>
#include "js/ProfilingStack.h"
#include <stdlib.h>
#include "mozilla/Atomics.h"
#ifndef SPS_STANDALONE
#include "nsISupportsImpl.h"
#endif
/* we duplicate this code here to avoid header dependencies
* which make it more difficult to include in other places */
#if defined(_M_X64) || defined(__x86_64__)
#define V8_HOST_ARCH_X64 1
#elif defined(_M_IX86) || defined(__i386__) || defined(__i386)
#define V8_HOST_ARCH_IA32 1
#elif defined(__ARMEL__)
#define V8_HOST_ARCH_ARM 1
#else
#warning Please add support for your architecture in chromium_types.h
#endif
// STORE_SEQUENCER: Because signals can interrupt our profile modification
// we need to make stores are not re-ordered by the compiler
// or hardware to make sure the profile is consistent at
// every point the signal can fire.
#ifdef V8_HOST_ARCH_ARM
// TODO Is there something cheaper that will prevent
// memory stores from being reordered
typedef void (*LinuxKernelMemoryBarrierFunc)(void);
LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
(LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
# define STORE_SEQUENCER() pLinuxKernelMemoryBarrier()
#elif defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_X64)
# if defined(_MSC_VER)
# include <intrin.h>
# define STORE_SEQUENCER() _ReadWriteBarrier();
# elif defined(__INTEL_COMPILER)
# define STORE_SEQUENCER() __memory_barrier();
# elif __GNUC__
# define STORE_SEQUENCER() asm volatile("" ::: "memory");
# else
# error "Memory clobber not supported for your compiler."
# endif
#else
# error "Memory clobber not supported for your platform."
#endif
// We can't include <algorithm> because it causes issues on OS X, so we use
// our own min function.
static inline uint32_t sMin(uint32_t l, uint32_t r) {
return l < r ? l : r;
}
// A stack entry exists to allow the JS engine to inform SPS of the current
// backtrace, but also to instrument particular points in C++ in case stack
// walking is not available on the platform we are running on.
//
// Each entry has a descriptive string, a relevant stack address, and some extra
// information the JS engine might want to inform SPS of. This class inherits
// from the JS engine's version of the entry to ensure that the size and layout
// of the two representations are consistent.
class StackEntry : public js::ProfileEntry
{
};
class ProfilerMarkerPayload;
template<typename T>
class ProfilerLinkedList;
class SpliceableJSONWriter;
class UniqueStacks;
class ProfilerMarker {
friend class ProfilerLinkedList<ProfilerMarker>;
public:
explicit ProfilerMarker(const char* aMarkerName,
ProfilerMarkerPayload* aPayload = nullptr,
double aTime = 0);
~ProfilerMarker();
const char* GetMarkerName() const {
return mMarkerName;
}
void StreamJSON(SpliceableJSONWriter& aWriter, UniqueStacks& aUniqueStacks) const;
void SetGeneration(uint32_t aGenID);
bool HasExpired(uint32_t aGenID) const {
return mGenID + 2 <= aGenID;
}
double GetTime() const;
private:
char* mMarkerName;
ProfilerMarkerPayload* mPayload;
ProfilerMarker* mNext;
double mTime;
uint32_t mGenID;
};
template<typename T>
class ProfilerLinkedList {
public:
ProfilerLinkedList()
: mHead(nullptr)
, mTail(nullptr)
{}
void insert(T* elem)
{
if (!mTail) {
mHead = elem;
mTail = elem;
} else {
mTail->mNext = elem;
mTail = elem;
}
elem->mNext = nullptr;
}
T* popHead()
{
if (!mHead) {
MOZ_ASSERT(false);
return nullptr;
}
T* head = mHead;
mHead = head->mNext;
if (!mHead) {
mTail = nullptr;
}
return head;
}
const T* peek() {
return mHead;
}
private:
T* mHead;
T* mTail;
};
typedef ProfilerLinkedList<ProfilerMarker> ProfilerMarkerLinkedList;
template<typename T>
class ProfilerSignalSafeLinkedList {
public:
ProfilerSignalSafeLinkedList()
: mSignalLock(false)
{}
~ProfilerSignalSafeLinkedList()
{
if (mSignalLock) {
// Some thread is modifying the list. We should only be released on that
// thread.
abort();
}
while (mList.peek()) {
delete mList.popHead();
}
}
// Insert an item into the list.
// Must only be called from the owning thread.
// Must not be called while the list from accessList() is being accessed.
// In the profiler, we ensure that by interrupting the profiled thread
// (which is the one that owns this list and calls insert() on it) until
// we're done reading the list from the signal handler.
void insert(T* aElement) {
MOZ_ASSERT(aElement);
mSignalLock = true;
STORE_SEQUENCER();
mList.insert(aElement);
STORE_SEQUENCER();
mSignalLock = false;
}
// Called within signal, from any thread, possibly while insert() is in the
// middle of modifying the list (on the owning thread). Will return null if
// that is the case.
// Function must be reentrant.
ProfilerLinkedList<T>* accessList()
{
if (mSignalLock) {
return nullptr;
}
return &mList;
}
private:
ProfilerLinkedList<T> mList;
// If this is set, then it's not safe to read the list because its contents
// are being changed.
volatile bool mSignalLock;
};
// Stub eventMarker function for js-engine event generation.
void ProfilerJSEventMarker(const char *event);
// the PseudoStack members are read by signal
// handlers, so the mutation of them needs to be signal-safe.
struct PseudoStack
{
public:
// Create a new PseudoStack and acquire a reference to it.
static PseudoStack *create()
{
return new PseudoStack();
}
// This is called on every profiler restart. Put things that should happen at that time here.
void reinitializeOnResume() {
// This is needed to cause an initial sample to be taken from sleeping threads. Otherwise sleeping
// threads would not have any samples to copy forward while sleeping.
mSleepId++;
}
void addMarker(const char* aMarkerStr, ProfilerMarkerPayload* aPayload, double aTime)
{
ProfilerMarker* marker = new ProfilerMarker(aMarkerStr, aPayload, aTime);
mPendingMarkers.insert(marker);
}
// called within signal. Function must be reentrant
ProfilerMarkerLinkedList* getPendingMarkers()
{
// The profiled thread is interrupted, so we can access the list safely.
// Unless the profiled thread was in the middle of changing the list when
// we interrupted it - in that case, accessList() will return null.
return mPendingMarkers.accessList();
}
void push(const char *aName, js::ProfileEntry::Category aCategory, uint32_t line)
{
push(aName, aCategory, nullptr, false, line);
}
void push(const char *aName, js::ProfileEntry::Category aCategory,
void *aStackAddress, bool aCopy, uint32_t line)
{
if (size_t(mStackPointer) >= mozilla::ArrayLength(mStack)) {
mStackPointer++;
return;
}
// In order to ensure this object is kept alive while it is
// active, we acquire a reference at the outermost push. This is
// released by the corresponding pop.
if (mStackPointer == 0) {
ref();
}
volatile StackEntry &entry = mStack[mStackPointer];
// Make sure we increment the pointer after the name has
// been written such that mStack is always consistent.
entry.initCppFrame(aStackAddress, line);
entry.setLabel(aName);
MOZ_ASSERT(entry.flags() == js::ProfileEntry::IS_CPP_ENTRY);
entry.setCategory(aCategory);
// Track if mLabel needs a copy.
if (aCopy)
entry.setFlag(js::ProfileEntry::FRAME_LABEL_COPY);
else
entry.unsetFlag(js::ProfileEntry::FRAME_LABEL_COPY);
// Prevent the optimizer from re-ordering these instructions
STORE_SEQUENCER();
mStackPointer++;
}
// Pop the stack. If the stack is empty and all other references to
// this PseudoStack have been dropped, then the PseudoStack is
// deleted and "false" is returned. Otherwise "true" is returned.
bool popAndMaybeDelete()
{
mStackPointer--;
if (mStackPointer == 0) {
// Release our self-owned reference count. See 'push'.
deref();
return false;
} else {
return true;
}
}
bool isEmpty()
{
return mStackPointer == 0;
}
uint32_t stackSize() const
{
return sMin(mStackPointer, mozilla::sig_safe_t(mozilla::ArrayLength(mStack)));
}
void sampleContext(JSContext* context) {
#ifndef SPS_STANDALONE
if (mContext && !context) {
// On JS shut down, flush the current buffer as stringifying JIT samples
// requires a live JSContext.
flushSamplerOnJSShutdown();
}
mContext = context;
if (!context) {
return;
}
static_assert(sizeof(mStack[0]) == sizeof(js::ProfileEntry),
"mStack must be binary compatible with js::ProfileEntry.");
js::SetContextProfilingStack(context,
(js::ProfileEntry*) mStack,
(uint32_t*) &mStackPointer,
(uint32_t) mozilla::ArrayLength(mStack));
if (mStartJSSampling)
enableJSSampling();
#endif
}
#ifndef SPS_STANDALONE
void enableJSSampling() {
if (mContext) {
js::EnableContextProfilingStack(mContext, true);
js::RegisterContextProfilingEventMarker(mContext, &ProfilerJSEventMarker);
mStartJSSampling = false;
} else {
mStartJSSampling = true;
}
}
void jsOperationCallback() {
if (mStartJSSampling)
enableJSSampling();
}
void disableJSSampling() {
mStartJSSampling = false;
if (mContext)
js::EnableContextProfilingStack(mContext, false);
}
#endif
// Keep a list of active checkpoints
StackEntry volatile mStack[1024];
private:
// A PseudoStack can only be created via the "create" method.
PseudoStack()
: mStackPointer(0)
, mSleepId(0)
, mSleepIdObserved(0)
, mSleeping(false)
, mRefCnt(1)
#ifndef SPS_STANDALONE
, mContext(nullptr)
#endif
, mStartJSSampling(false)
, mPrivacyMode(false)
{
MOZ_COUNT_CTOR(PseudoStack);
}
// A PseudoStack can only be deleted via deref.
~PseudoStack() {
MOZ_COUNT_DTOR(PseudoStack);
if (mStackPointer != 0) {
// We're releasing the pseudostack while it's still in use.
// The label macros keep a non ref counted reference to the
// stack to avoid a TLS. If these are not all cleared we will
// get a use-after-free so better to crash now.
abort();
}
}
// No copying.
PseudoStack(const PseudoStack&) = delete;
void operator=(const PseudoStack&) = delete;
void flushSamplerOnJSShutdown();
// Keep a list of pending markers that must be moved
// to the circular buffer
ProfilerSignalSafeLinkedList<ProfilerMarker> mPendingMarkers;
// This may exceed the length of mStack, so instead use the stackSize() method
// to determine the number of valid samples in mStack
mozilla::sig_safe_t mStackPointer;
// Incremented at every sleep/wake up of the thread
int mSleepId;
// Previous id observed. If this is not the same as mSleepId, this thread is not sleeping in the same place any more
mozilla::Atomic<int> mSleepIdObserved;
// Keeps tack of whether the thread is sleeping or not (1 when sleeping 0 when awake)
mozilla::Atomic<int> mSleeping;
// This class is reference counted because it must be kept alive by
// the ThreadInfo, by the reference from tlsPseudoStack, and by the
// current thread when callbacks are in progress.
mozilla::Atomic<int> mRefCnt;
public:
#ifndef SPS_STANDALONE
// The context which is being sampled
JSContext *mContext;
#endif
// Start JS Profiling when possible
bool mStartJSSampling;
bool mPrivacyMode;
enum SleepState {NOT_SLEEPING, SLEEPING_FIRST, SLEEPING_AGAIN};
// The first time this is called per sleep cycle we return SLEEPING_FIRST
// and any other subsequent call within the same sleep cycle we return SLEEPING_AGAIN
SleepState observeSleeping() {
if (mSleeping != 0) {
if (mSleepIdObserved == mSleepId) {
return SLEEPING_AGAIN;
} else {
mSleepIdObserved = mSleepId;
return SLEEPING_FIRST;
}
} else {
return NOT_SLEEPING;
}
}
// Call this whenever the current thread sleeps or wakes up
// Calling setSleeping with the same value twice in a row is an error
void setSleeping(int sleeping) {
MOZ_ASSERT(mSleeping != sleeping);
mSleepId++;
mSleeping = sleeping;
}
bool isSleeping() {
return !!mSleeping;
}
void ref() {
++mRefCnt;
}
void deref() {
int newValue = --mRefCnt;
if (newValue == 0) {
delete this;
}
}
};
#endif
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