Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 537 insertions, 0 deletions

diff --git a/tools/profiler/public/ProfilerThreadRegistrationData.h b/tools/profiler/public/ProfilerThreadRegistrationData.h
new file mode 100644
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+// This header contains classes that hold data related to thread profiling:
+// Data members are stored `protected` in `ThreadRegistrationData`.
+// Non-virtual sub-classes of ProfilerThreadRegistrationData provide layers of
+// public accessors to subsets of the data. Each level builds on the previous
+// one and adds further access to more data, but always with the appropriate
+// guards where necessary.
+// These classes have protected constructors, so only some trusted classes
+// `ThreadRegistration` and `ThreadRegistry` will be able to construct them, and
+// then give limited access depending on who asks (the owning thread or another
+// one), and how much data they actually need.
+//
+// The hierarchy is, from base to most derived:
+// - ThreadRegistrationData
+// - ThreadRegistrationUnlockedConstReader
+// - ThreadRegistrationUnlockedConstReaderAndAtomicRW
+// - ThreadRegistrationUnlockedRWForLockedProfiler
+// - ThreadRegistrationUnlockedReaderAndAtomicRWOnThread
+// - ThreadRegistrationLockedRWFromAnyThread
+// - ThreadRegistrationLockedRWOnThread
+// - ThreadRegistration::EmbeddedData (actual data member in ThreadRegistration)
+//
+// Tech detail: These classes need to be a single hierarchy so that
+// `ThreadRegistration` can contain the most-derived class, and from there can
+// publish references to base classes without relying on Undefined Behavior.
+// (It's not allowed to have some object and give a reference to a sub-class,
+// unless that object was *really* constructed as that sub-class at least, even
+// if that sub-class only adds member functions!)
+// And where appropriate, these references will come along with the required
+// lock.
+
+#ifndef ProfilerThreadRegistrationData_h
+#define ProfilerThreadRegistrationData_h
+
+#include "js/ProfilingFrameIterator.h"
+#include "js/ProfilingStack.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/BaseProfilerDetail.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/ProfilerThreadPlatformData.h"
+#include "mozilla/ProfilerThreadRegistrationInfo.h"
+#include "nsCOMPtr.h"
+#include "nsIThread.h"
+
+class ProfiledThreadData;
+class PSAutoLock;
+struct JSContext;
+
+// Enum listing which profiling features are active for a single thread.
+enum class ThreadProfilingFeatures : uint32_t {
+  // The thread is not being profiled at all (either the profiler is not
+  // running, or this thread is not examined during profiling.)
+  NotProfiled = 0u,
+
+  // Single features, binary exclusive. May be `Combine()`d.
+  CPUUtilization = 1u << 0,
+  Sampling = 1u << 1,
+  Markers = 1u << 2,
+
+  // All possible features. Usually used as a mask to see if any feature is
+  // active at a given time.
+  Any = CPUUtilization | Sampling | Markers
+};
+
+// Binary OR of one of more ThreadProfilingFeatures, to mix all arguments.
+template <typename... Ts>
+[[nodiscard]] constexpr ThreadProfilingFeatures Combine(
+    ThreadProfilingFeatures a1, Ts... as) {
+  static_assert((true && ... &&
+                 std::is_same_v<std::remove_cv_t<std::remove_reference_t<Ts>>,
+                                ThreadProfilingFeatures>));
+  return static_cast<ThreadProfilingFeatures>(
+      (static_cast<std::underlying_type_t<ThreadProfilingFeatures>>(a1) | ... |
+       static_cast<std::underlying_type_t<ThreadProfilingFeatures>>(as)));
+}
+
+// Binary AND of one of more ThreadProfilingFeatures, to find features common to
+// all arguments.
+template <typename... Ts>
+[[nodiscard]] constexpr ThreadProfilingFeatures Intersect(
+    ThreadProfilingFeatures a1, Ts... as) {
+  static_assert((true && ... &&
+                 std::is_same_v<std::remove_cv_t<std::remove_reference_t<Ts>>,
+                                ThreadProfilingFeatures>));
+  return static_cast<ThreadProfilingFeatures>(
+      (static_cast<std::underlying_type_t<ThreadProfilingFeatures>>(a1) & ... &
+       static_cast<std::underlying_type_t<ThreadProfilingFeatures>>(as)));
+}
+
+// Are there features in common between the two given sets?
+// Mostly useful to test if any of a set of features is present in another set.
+template <typename... Ts>
+[[nodiscard]] constexpr bool DoFeaturesIntersect(ThreadProfilingFeatures a1,
+                                                 ThreadProfilingFeatures a2) {
+  return Intersect(a1, a2) != ThreadProfilingFeatures::NotProfiled;
+}
+
+namespace mozilla::profiler {
+
+// All data members related to thread profiling are stored here.
+// See derived classes below, which give limited unlocked/locked read/write
+// access in different situations, and will be available through
+// ThreadRegistration and ThreadRegistry.
+class ThreadRegistrationData {
+ public:
+  // No public accessors here. See derived classes for accessors, and
+  // Get.../With... functions for who can use these accessors.
+
+  size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+    // Not including data that is not fully owned here.
+    return 0;
+  }
+
+  size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+    return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+  }
+
+  static constexpr size_t MAX_JS_FRAMES = 1024;
+  using JsFrame = JS::ProfilingFrameIterator::Frame;
+  using JsFrameBuffer = JsFrame[MAX_JS_FRAMES];
+
+  // `protected` to allow derived classes to read all data members.
+ protected:
+  ThreadRegistrationData(const char* aName, const void* aStackTop);
+
+#ifdef DEBUG
+  // Destructor only used to check invariants.
+  ~ThreadRegistrationData() {
+    MOZ_ASSERT((mProfilingFeatures != ThreadProfilingFeatures::NotProfiled) ==
+               !!mProfiledThreadData);
+    MOZ_ASSERT(!mProfiledThreadData,
+               "mProfiledThreadData pointer should have been reset before "
+               "~ThreadRegistrationData");
+  }
+#endif  // DEBUG
+
+  // Permanent thread information.
+  // Set at construction, read from anywhere, moved-from at destruction.
+  ThreadRegistrationInfo mInfo;
+
+  // Contains profiler labels and JS frames.
+  // Deep-written on thread only, deep-read from thread and suspended thread.
+  ProfilingStack mProfilingStack;
+
+  // In practice, only read from thread and suspended thread.
+  PlatformData mPlatformData;
+
+  // Only read from thread and suspended thread.
+  const void* const mStackTop;
+
+  // Written from thread, read from thread and suspended thread.
+  nsCOMPtr<nsIThread> mThread;
+
+  // If this is a JS thread, this is its JSContext, which is required for any
+  // JS sampling.
+  // Written from thread, read from thread and suspended thread.
+  JSContext* mJSContext = nullptr;
+
+  // If mJSContext is not null AND the thread is being profiled, this points at
+  // the start of a JsFrameBuffer to be used for on-thread synchronous sampling.
+  JsFrame* mJsFrameBuffer = nullptr;
+
+  // The profiler needs to start and stop JS sampling of JS threads at various
+  // times. However, the JS engine can only do the required actions on the
+  // JS thread itself ("on-thread"), not from another thread ("off-thread").
+  // Therefore, we have the following two-step process.
+  //
+  // - The profiler requests (on-thread or off-thread) that the JS sampling be
+  //   started/stopped, by changing mJSSampling to the appropriate REQUESTED
+  //   state.
+  //
+  // - The relevant JS thread polls (on-thread) for changes to mJSSampling.
+  //   When it sees a REQUESTED state, it performs the appropriate actions to
+  //   actually start/stop JS sampling, and changes mJSSampling out of the
+  //   REQUESTED state.
+  //
+  // The state machine is as follows.
+  //
+  //             INACTIVE --> ACTIVE_REQUESTED
+  //                  ^       ^ |
+  //                  |     _/  |
+  //                  |   _/    |
+  //                  |  /      |
+  //                  | v       v
+  //   INACTIVE_REQUESTED <-- ACTIVE
+  //
+  // The polling is done in the following two ways.
+  //
+  // - Via the interrupt callback mechanism; the JS thread must call
+  //   profiler_js_interrupt_callback() from its own interrupt callback.
+  //   This is how sampling must be started/stopped for threads where the
+  //   request was made off-thread.
+  //
+  // - When {Start,Stop}JSSampling() is called on-thread, we can immediately
+  //   follow it with a PollJSSampling() call to avoid the delay between the
+  //   two steps. Likewise, setJSContext() calls PollJSSampling().
+  //
+  // One non-obvious thing about all this: these JS sampling requests are made
+  // on all threads, even non-JS threads. mContext needs to also be set (via
+  // setJSContext(), which can only happen for JS threads) for any JS sampling
+  // to actually happen.
+  //
+  enum {
+    INACTIVE = 0,
+    ACTIVE_REQUESTED = 1,
+    ACTIVE = 2,
+    INACTIVE_REQUESTED = 3,
+  } mJSSampling = INACTIVE;
+
+  uint32_t mJSFlags = 0;
+
+  // Flags to conveniently track various JS instrumentations.
+  enum class JSInstrumentationFlags {
+    StackSampling = 0x1,
+    Allocations = 0x2,
+  };
+
+  [[nodiscard]] bool JSAllocationsEnabled() const {
+    return mJSFlags & uint32_t(JSInstrumentationFlags::Allocations);
+  }
+
+  // The following members may be modified from another thread.
+  // They need to be atomic, because LockData() does not prevent reads from
+  // the owning thread.
+
+  // mSleep tracks whether the thread is sleeping, and if so, whether it has
+  // been previously observed. This is used for an optimization: in some
+  // cases, when a thread is asleep, we duplicate the previous sample, which
+  // is cheaper than taking a new sample.
+  //
+  // mSleep is atomic because it is accessed from multiple threads.
+  //
+  // - It is written only by this thread, via setSleeping() and setAwake().
+  //
+  // - It is read by SamplerThread::Run().
+  //
+  // There are two cases where racing between threads can cause an issue.
+  //
+  // - If CanDuplicateLastSampleDueToSleep() returns false but that result is
+  //   invalidated before being acted upon, we will take a full sample
+  //   unnecessarily. This is additional work but won't cause any correctness
+  //   issues. (In actual fact, this case is impossible. In order to go from
+  //   CanDuplicateLastSampleDueToSleep() returning false to it returning true
+  //   requires an intermediate call to it in order for mSleep to go from
+  //   SLEEPING_NOT_OBSERVED to SLEEPING_OBSERVED.)
+  //
+  // - If CanDuplicateLastSampleDueToSleep() returns true but that result is
+  //   invalidated before being acted upon -- i.e. the thread wakes up before
+  //   DuplicateLastSample() is called -- we will duplicate the previous
+  //   sample. This is inaccurate, but only slightly... we will effectively
+  //   treat the thread as having slept a tiny bit longer than it really did.
+  //
+  // This latter inaccuracy could be avoided by moving the
+  // CanDuplicateLastSampleDueToSleep() check within the thread-freezing code,
+  // e.g. the section where Tick() is called. But that would reduce the
+  // effectiveness of the optimization because more code would have to be run
+  // before we can tell that duplication is allowed.
+  //
+  static const int AWAKE = 0;
+  static const int SLEEPING_NOT_OBSERVED = 1;
+  static const int SLEEPING_OBSERVED = 2;
+  // Read&written from thread and suspended thread.
+  Atomic<int> mSleep{AWAKE};
+  Atomic<uint64_t> mThreadCpuTimeInNsAtLastSleep{0};
+
+#ifdef NIGHTLY_BUILD
+  // The first wake is the thread creation.
+  Atomic<uint64_t, MemoryOrdering::Relaxed> mWakeCount{1};
+  mutable baseprofiler::detail::BaseProfilerMutex mRecordWakeCountMutex;
+  mutable uint64_t mAlreadyRecordedWakeCount = 0;
+  mutable uint64_t mAlreadyRecordedCpuTimeInMs = 0;
+#endif
+
+  // Is this thread currently being profiled, and with which features?
+  // Written from profiler, read from any thread.
+  // Invariant: `!!mProfilingFeatures == !!mProfiledThreadData` (set together.)
+  Atomic<ThreadProfilingFeatures, MemoryOrdering::Relaxed> mProfilingFeatures{
+      ThreadProfilingFeatures::NotProfiled};
+
+  // If the profiler is active and this thread is selected for profiling, this
+  // points at the relevant ProfiledThreadData.
+  // Fully controlled by the profiler.
+  // Invariant: `!!mProfilingFeatures == !!mProfiledThreadData` (set together).
+  ProfiledThreadData* mProfiledThreadData = nullptr;
+};
+
+// Accessing const data from any thread.
+class ThreadRegistrationUnlockedConstReader : public ThreadRegistrationData {
+ public:
+  [[nodiscard]] const ThreadRegistrationInfo& Info() const { return mInfo; }
+
+  [[nodiscard]] const PlatformData& PlatformDataCRef() const {
+    return mPlatformData;
+  }
+
+  [[nodiscard]] const void* StackTop() const { return mStackTop; }
+
+ protected:
+  ThreadRegistrationUnlockedConstReader(const char* aName,
+                                        const void* aStackTop)
+      : ThreadRegistrationData(aName, aStackTop) {}
+};
+
+// Accessing atomic data from any thread.
+class ThreadRegistrationUnlockedConstReaderAndAtomicRW
+    : public ThreadRegistrationUnlockedConstReader {
+ public:
+  [[nodiscard]] const ProfilingStack& ProfilingStackCRef() const {
+    return mProfilingStack;
+  }
+  [[nodiscard]] ProfilingStack& ProfilingStackRef() { return mProfilingStack; }
+
+  // Similar to `profiler_is_active()`, this atomic flag may become out-of-date.
+  // It should only be used as an indication to know whether this thread is
+  // probably being profiled (with some specific features), to avoid doing
+  // expensive operations otherwise. Edge cases:
+  // - This thread could get `NotProfiled`, but the profiler has just started,
+  //   so some very early data may be missing. No real impact on profiling.
+  // - This thread could see profiled features, but the profiled has just
+  //   stopped, so some some work will be done and then discarded when finally
+  //   attempting to write to the buffer. No impact on profiling.
+  // - This thread could see profiled features, but the profiler will quickly
+  //   stop and restart, so this thread will write information relevant to the
+  //   previous profiling session. Very rare, and little impact on profiling.
+  [[nodiscard]] ThreadProfilingFeatures ProfilingFeatures() const {
+    return mProfilingFeatures;
+  }
+
+  // Call this whenever the current thread sleeps. Calling it twice in a row
+  // without an intervening setAwake() call is an error.
+  void SetSleeping() {
+    MOZ_ASSERT(mSleep == AWAKE);
+    mSleep = SLEEPING_NOT_OBSERVED;
+  }
+
+  // Call this whenever the current thread wakes. Calling it twice in a row
+  // without an intervening setSleeping() call is an error.
+  void SetAwake() {
+    MOZ_ASSERT(mSleep != AWAKE);
+    mSleep = AWAKE;
+#ifdef NIGHTLY_BUILD
+    ++mWakeCount;
+#endif
+  }
+
+  // Returns the CPU time used by the thread since the previous call to this
+  // method or since the thread was started if this is the first call.
+  uint64_t GetNewCpuTimeInNs() {
+    uint64_t newCpuTimeNs;
+    if (!GetCpuTimeSinceThreadStartInNs(&newCpuTimeNs, PlatformDataCRef())) {
+      newCpuTimeNs = 0;
+    }
+    uint64_t before = mThreadCpuTimeInNsAtLastSleep;
+    uint64_t result =
+        MOZ_LIKELY(newCpuTimeNs > before) ? newCpuTimeNs - before : 0;
+    mThreadCpuTimeInNsAtLastSleep = newCpuTimeNs;
+    return result;
+  }
+
+#ifdef NIGHTLY_BUILD
+  void RecordWakeCount() const;
+#endif
+
+  // 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 that had been observed prior to the profiler stopping and
+    // restarting. Otherwise sleeping threads would not have any samples to
+    // copy forward while sleeping.
+    (void)mSleep.compareExchange(SLEEPING_OBSERVED, SLEEPING_NOT_OBSERVED);
+  }
+
+  // This returns true for the second and subsequent calls in each sleep
+  // cycle, so that the sampler can skip its full sampling and reuse the first
+  // asleep sample instead.
+  [[nodiscard]] bool CanDuplicateLastSampleDueToSleep() {
+    if (mSleep == AWAKE) {
+      return false;
+    }
+    if (mSleep.compareExchange(SLEEPING_NOT_OBSERVED, SLEEPING_OBSERVED)) {
+      return false;
+    }
+    return true;
+  }
+
+  [[nodiscard]] bool IsSleeping() const { return mSleep != AWAKE; }
+
+ protected:
+  ThreadRegistrationUnlockedConstReaderAndAtomicRW(const char* aName,
+                                                   const void* aStackTop)
+      : ThreadRegistrationUnlockedConstReader(aName, aStackTop) {}
+};
+
+// Like above, with special PSAutoLock-guarded accessors.
+class ThreadRegistrationUnlockedRWForLockedProfiler
+    : public ThreadRegistrationUnlockedConstReaderAndAtomicRW {
+ public:
+  // IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT!
+  // Only add functions that take a `const PSAutoLock&` proof-of-lock.
+  // (Because there is no other lock.)
+
+  [[nodiscard]] const ProfiledThreadData* GetProfiledThreadData(
+      const PSAutoLock&) const {
+    return mProfiledThreadData;
+  }
+
+  [[nodiscard]] ProfiledThreadData* GetProfiledThreadData(const PSAutoLock&) {
+    return mProfiledThreadData;
+  }
+
+ protected:
+  ThreadRegistrationUnlockedRWForLockedProfiler(const char* aName,
+                                                const void* aStackTop)
+      : ThreadRegistrationUnlockedConstReaderAndAtomicRW(aName, aStackTop) {}
+};
+
+// Reading data, unlocked from the thread, or locked otherwise.
+// This data MUST only be written from the thread with lock (i.e., in
+// LockedRWOnThread through RWOnThreadWithLock.)
+class ThreadRegistrationUnlockedReaderAndAtomicRWOnThread
+    : public ThreadRegistrationUnlockedRWForLockedProfiler {
+ public:
+  // IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT!
+  // Non-atomic members read here MUST be written from LockedRWOnThread (to
+  // guarantee that they are only modified on this thread.)
+
+  [[nodiscard]] JSContext* GetJSContext() const { return mJSContext; }
+
+ protected:
+  ThreadRegistrationUnlockedReaderAndAtomicRWOnThread(const char* aName,
+                                                      const void* aStackTop)
+      : ThreadRegistrationUnlockedRWForLockedProfiler(aName, aStackTop) {}
+};
+
+// Accessing locked data from the thread, or from any thread through the locked
+// profiler:
+
+// Like above, and profiler can also read&write mutex-protected members.
+class ThreadRegistrationLockedRWFromAnyThread
+    : public ThreadRegistrationUnlockedReaderAndAtomicRWOnThread {
+ public:
+  void SetProfilingFeaturesAndData(ThreadProfilingFeatures aProfilingFeatures,
+                                   ProfiledThreadData* aProfiledThreadData,
+                                   const PSAutoLock&);
+  void ClearProfilingFeaturesAndData(const PSAutoLock&);
+
+  // Not null when JSContext is not null AND this thread is being profiled.
+  // Points at the start of JsFrameBuffer.
+  [[nodiscard]] JsFrame* GetJsFrameBuffer() const { return mJsFrameBuffer; }
+
+  [[nodiscard]] const nsCOMPtr<nsIEventTarget> GetEventTarget() const {
+    return mThread;
+  }
+
+  void ResetMainThread(nsIThread* aThread) { mThread = aThread; }
+
+  // aDelay is the time the event that is currently running on the thread was
+  // queued before starting to run (if a PrioritizedEventQueue
+  // (i.e. MainThread), this will be 0 for any event at a lower priority
+  // than Input).
+  // aRunning is the time the event has been running. If no event is running
+  // these will both be TimeDuration() (i.e. 0). Both are out params, and are
+  // always set. Their initial value is discarded.
+  void GetRunningEventDelay(const TimeStamp& aNow, TimeDuration& aDelay,
+                            TimeDuration& aRunning) {
+    if (mThread) {  // can be null right at the start of a process
+      TimeStamp start;
+      mThread->GetRunningEventDelay(&aDelay, &start);
+      if (!start.IsNull()) {
+        // Note: the timestamp used here will be from when we started to
+        // suspend and sample the thread; which is also the timestamp
+        // associated with the sample.
+        aRunning = aNow - start;
+        return;
+      }
+    }
+    aDelay = TimeDuration();
+    aRunning = TimeDuration();
+  }
+
+  // Request that this thread start JS sampling. JS sampling won't actually
+  // start until a subsequent PollJSSampling() call occurs *and* mContext has
+  // been set.
+  void StartJSSampling(uint32_t aJSFlags) {
+    // This function runs on-thread or off-thread.
+
+    MOZ_RELEASE_ASSERT(mJSSampling == INACTIVE ||
+                       mJSSampling == INACTIVE_REQUESTED);
+    mJSSampling = ACTIVE_REQUESTED;
+    mJSFlags = aJSFlags;
+  }
+
+  // Request that this thread stop JS sampling. JS sampling won't actually
+  // stop until a subsequent PollJSSampling() call occurs.
+  void StopJSSampling() {
+    // This function runs on-thread or off-thread.
+
+    MOZ_RELEASE_ASSERT(mJSSampling == ACTIVE ||
+                       mJSSampling == ACTIVE_REQUESTED);
+    mJSSampling = INACTIVE_REQUESTED;
+  }
+
+ protected:
+  ThreadRegistrationLockedRWFromAnyThread(const char* aName,
+                                          const void* aStackTop)
+      : ThreadRegistrationUnlockedReaderAndAtomicRWOnThread(aName, aStackTop) {}
+};
+
+// Accessing data, locked, from the thread.
+// If any non-atomic data is readable from UnlockedReaderAndAtomicRWOnThread,
+// it must be written from here, and not in base classes: Since this data is
+// only written on the thread, it can be read from the same thread without
+// lock; but writing must be locked so that other threads can safely read it,
+// typically from LockedRWFromAnyThread.
+class ThreadRegistrationLockedRWOnThread
+    : public ThreadRegistrationLockedRWFromAnyThread {
+ public:
+  void SetJSContext(JSContext* aJSContext);
+  void ClearJSContext();
+
+  // Poll to see if JS sampling should be started/stopped.
+  void PollJSSampling();
+
+ public:
+  ThreadRegistrationLockedRWOnThread(const char* aName, const void* aStackTop)
+      : ThreadRegistrationLockedRWFromAnyThread(aName, aStackTop) {}
+};
+
+}  // namespace mozilla::profiler
+
+#endif  // ProfilerThreadRegistrationData_h