mozglue/misc/AutoProfilerLabel.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/AutoProfilerLabel.h"
   8
   9 #include "mozilla/Assertions.h"
  10 #include "mozilla/PlatformMutex.h"
  11
  12 namespace mozilla {
  13
  14 // RAII class that encapsulates all shared static data, and enforces locking
  15 // when accessing this data.
  16 class MOZ_RAII AutoProfilerLabelData {
  17  public:
  18   AutoProfilerLabelData() { sAPLMutex.Lock(); }
  19
  20   ~AutoProfilerLabelData() { sAPLMutex.Unlock(); }
  21
  22   AutoProfilerLabelData(const AutoProfilerLabelData&) = delete;
  23   void operator=(const AutoProfilerLabelData&) = delete;
  24
  25   const ProfilerLabelEnter& EnterCRef() const { return sEnter; }
  26   ProfilerLabelEnter& EnterRef() { return sEnter; }
  27
  28   const ProfilerLabelExit& ExitCRef() const { return sExit; }
  29   ProfilerLabelExit& ExitRef() { return sExit; }
  30
  31   const uint32_t& GenerationCRef() const { return sGeneration; }
  32   uint32_t& GenerationRef() { return sGeneration; }
  33
  34   static bool RacyIsProfilerPresent() { return !!sGeneration; }
  35
  36  private:
  37   // Thin shell around mozglue PlatformMutex, for local internal use.
  38   // Does not preserve behavior in JS record/replay.
  39   class Mutex : private mozilla::detail::MutexImpl {
  40    public:
  41     Mutex() = default;
  42     void Lock() { mozilla::detail::MutexImpl::lock(); }
  43     void Unlock() { mozilla::detail::MutexImpl::unlock(); }
  44   };
  45
  46   // Mutex protecting access to the following static members.
  47   static Mutex sAPLMutex MOZ_UNANNOTATED;
  48
  49   static ProfilerLabelEnter sEnter;
  50   static ProfilerLabelExit sExit;
  51
  52   // Current "generation" of RegisterProfilerLabelEnterExit calls.
  53   static uint32_t sGeneration;
  54 };
  55
  56 /* static */ AutoProfilerLabelData::Mutex AutoProfilerLabelData::sAPLMutex;
  57 /* static */ ProfilerLabelEnter AutoProfilerLabelData::sEnter = nullptr;
  58 /* static */ ProfilerLabelExit AutoProfilerLabelData::sExit = nullptr;
  59 /* static */ uint32_t AutoProfilerLabelData::sGeneration = 0;
  60
  61 void RegisterProfilerLabelEnterExit(ProfilerLabelEnter aEnter,
  62                                     ProfilerLabelExit aExit) {
  63   MOZ_ASSERT(!aEnter == !aExit, "Must provide both null or both non-null");
  64
  65   AutoProfilerLabelData data;
  66   MOZ_ASSERT(!aEnter != !data.EnterRef(),
  67              "Must go from null to non-null, or from non-null to null");
  68   data.EnterRef() = aEnter;
  69   data.ExitRef() = aExit;
  70   ++data.GenerationRef();
  71 }
  72
  73 bool IsProfilerPresent() {
  74   return AutoProfilerLabelData::RacyIsProfilerPresent();
  75 }
  76
  77 ProfilerLabel ProfilerLabelBegin(const char* aLabelName,
  78                                  const char* aDynamicString, void* aSp) {
  79   const AutoProfilerLabelData data;
  80   void* entryContext = (data.EnterCRef())
  81                            ? data.EnterCRef()(aLabelName, aDynamicString, aSp)
  82                            : nullptr;
  83   uint32_t generation = data.GenerationCRef();
  84
  85   return std::make_tuple(entryContext, generation);
  86 }
  87
  88 void ProfilerLabelEnd(const ProfilerLabel& aLabel) {
  89   if (!IsValidProfilerLabel(aLabel)) {
  90     return;
  91   }
  92
  93   const AutoProfilerLabelData data;
  94   if (data.ExitCRef() && (std::get<1>(aLabel) == data.GenerationCRef())) {
  95     data.ExitCRef()(std::get<0>(aLabel));
  96   }
  97 }
  98
  99 AutoProfilerLabel::AutoProfilerLabel(const char* aLabel,
 100                                      const char* aDynamicString) {
 101   std::tie(mEntryContext, mGeneration) =
 102       ProfilerLabelBegin(aLabel, aDynamicString, this);
 103 }
 104
 105 AutoProfilerLabel::~AutoProfilerLabel() {
 106   ProfilerLabelEnd(std::make_tuple(mEntryContext, mGeneration));
 107 }
 108
 109 }  // namespace mozilla