DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Implementation

Mercurial (b6d82b1a6b02)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=8 et ft=cpp : */
/* 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 mozilla_ShmemPool_h
#define mozilla_ShmemPool_h

#include "mozilla/ipc/Shmem.h"
#include "mozilla/Mutex.h"

extern mozilla::LazyLogModule sShmemPoolLog;
#define SHMEMPOOL_LOG(args) \
  MOZ_LOG(sShmemPoolLog, mozilla::LogLevel::Debug, args)
#define SHMEMPOOL_LOG_WARN(args) \
  MOZ_LOG(sShmemPoolLog, mozilla::LogLevel::Warning, args)
#define SHMEMPOOL_LOG_ERROR(args) \
  MOZ_LOG(sShmemPoolLog, mozilla::LogLevel::Error, args)

namespace mozilla {

class ShmemPool;

class ShmemBuffer {
 public:
  ShmemBuffer() : mInitialized(false) {}
  explicit ShmemBuffer(mozilla::ipc::Shmem aShmem) {
    mInitialized = true;
    mShmem = aShmem;
  }

  ShmemBuffer(ShmemBuffer&& rhs) {
    mInitialized = rhs.mInitialized;
    mShmem = std::move(rhs.mShmem);
  }

  ShmemBuffer& operator=(ShmemBuffer&& rhs) {
    MOZ_ASSERT(&rhs != this, "self-moves are prohibited");
    mInitialized = rhs.mInitialized;
    mShmem = std::move(rhs.mShmem);
    return *this;
  }

  // No copies allowed
  ShmemBuffer(const ShmemBuffer&) = delete;
  ShmemBuffer& operator=(const ShmemBuffer&) = delete;

  bool Valid() { return mInitialized; }

  uint8_t* GetBytes() { return mShmem.get<uint8_t>(); }

  mozilla::ipc::Shmem& Get() { return mShmem; }

 private:
  friend class ShmemPool;

  bool mInitialized;
  mozilla::ipc::Shmem mShmem;
};

class ShmemPool {
 public:
  explicit ShmemPool(size_t aPoolSize);
  ~ShmemPool();
  // Get/GetIfAvailable differ in what thread they can run on. GetIfAvailable
  // can run anywhere but won't allocate if the right size isn't available.
  ShmemBuffer GetIfAvailable(size_t aSize);
  void Put(ShmemBuffer&& aShmem);

  // We need to use the allocation/deallocation functions
  // of a specific IPC child/parent instance.
  template <class T>
  void Cleanup(T* aInstance) {
    MutexAutoLock lock(mMutex);
    for (size_t i = 0; i < mShmemPool.Length(); i++) {
      if (mShmemPool[i].mInitialized) {
        aInstance->DeallocShmem(mShmemPool[i].Get());
        mShmemPool[i].mInitialized = false;
      }
    }
  }

  template <class T>
  ShmemBuffer Get(T* aInstance, size_t aSize) {
    MutexAutoLock lock(mMutex);

    // Pool is empty, don't block caller.
    if (mPoolFree == 0) {
      if (!mErrorLogged) {
        // log "out of pool" once as error to avoid log spam
        mErrorLogged = true;
        SHMEMPOOL_LOG_ERROR(
            ("ShmemPool is empty, future occurrences "
             "will be logged as warnings"));
      } else {
        SHMEMPOOL_LOG_WARN(("ShmemPool is empty"));
      }
      // This isn't initialized, so will be understood as an error.
      return ShmemBuffer();
    }

    ShmemBuffer& res = mShmemPool[mPoolFree - 1];

    if (!res.mInitialized) {
      SHMEMPOOL_LOG(("Initializing new Shmem in pool"));
      if (!aInstance->AllocShmem(aSize, ipc::SharedMemory::TYPE_BASIC,
                                 &res.mShmem)) {
        SHMEMPOOL_LOG(("Failure allocating new Shmem buffer"));
        return ShmemBuffer();
      }
      res.mInitialized = true;
    }

    MOZ_ASSERT(res.mShmem.IsWritable(), "Shmem in Pool is not writable?");

    // Prepare buffer, increase size if needed (we never shrink as we don't
    // maintain seperate sized pools and we don't want to keep reallocating)
    if (res.mShmem.Size<char>() < aSize) {
      SHMEMPOOL_LOG(("Size change/increase in Shmem Pool"));
      aInstance->DeallocShmem(res.mShmem);
      res.mInitialized = false;
      // this may fail; always check return value
      if (!aInstance->AllocShmem(aSize, ipc::SharedMemory::TYPE_BASIC,
                                 &res.mShmem)) {
        SHMEMPOOL_LOG(("Failure allocating resized Shmem buffer"));
        return ShmemBuffer();
      } else {
        res.mInitialized = true;
      }
    }

    MOZ_ASSERT(res.mShmem.IsWritable(),
               "Shmem in Pool is not writable post resize?");

    mPoolFree--;
#ifdef DEBUG
    size_t poolUse = mShmemPool.Length() - mPoolFree;
    if (poolUse > mMaxPoolUse) {
      mMaxPoolUse = poolUse;
      SHMEMPOOL_LOG(
          ("Maximum ShmemPool use increased: %zu buffers", mMaxPoolUse));
    }
#endif
    return std::move(res);
  }

 private:
  Mutex mMutex;
  size_t mPoolFree;
  bool mErrorLogged;
#ifdef DEBUG
  size_t mMaxPoolUse;
#endif
  nsTArray<ShmemBuffer> mShmemPool;
};

}  // namespace mozilla

#endif  // mozilla_ShmemPool_h